Java tutorial
/* * Copyright (c) 1994, 2019, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.lang; import java.io.BufferedInputStream; import java.io.BufferedOutputStream; import java.io.Console; import java.io.FileDescriptor; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.PrintStream; import java.io.UnsupportedEncodingException; import java.lang.annotation.Annotation; import java.lang.module.ModuleDescriptor; import java.lang.reflect.Constructor; import java.lang.reflect.Executable; import java.lang.reflect.Method; import java.lang.reflect.Modifier; import java.net.URI; import java.nio.charset.CharacterCodingException; import java.security.AccessControlContext; import java.security.ProtectionDomain; import java.security.AccessController; import java.security.PrivilegedAction; import java.nio.channels.Channel; import java.nio.channels.spi.SelectorProvider; import java.nio.charset.Charset; import java.util.Iterator; import java.util.List; import java.util.Map; import java.util.Objects; import java.util.Properties; import java.util.PropertyPermission; import java.util.ResourceBundle; import java.util.function.Supplier; import java.util.concurrent.ConcurrentHashMap; import java.util.stream.Stream; import jdk.internal.util.StaticProperty; import jdk.internal.module.ModuleBootstrap; import jdk.internal.module.ServicesCatalog; import jdk.internal.reflect.CallerSensitive; import jdk.internal.reflect.Reflection; import jdk.internal.HotSpotIntrinsicCandidate; import jdk.internal.access.JavaLangAccess; import jdk.internal.access.SharedSecrets; import jdk.internal.misc.VM; import jdk.internal.logger.LoggerFinderLoader; import jdk.internal.logger.LazyLoggers; import jdk.internal.logger.LocalizedLoggerWrapper; import jdk.internal.util.SystemProps; import jdk.internal.vm.annotation.Stable; import sun.reflect.annotation.AnnotationType; import sun.nio.ch.Interruptible; import sun.security.util.SecurityConstants; /** * The {@code System} class contains several useful class fields * and methods. It cannot be instantiated. * * Among the facilities provided by the {@code System} class * are standard input, standard output, and error output streams; * access to externally defined properties and environment * variables; a means of loading files and libraries; and a utility * method for quickly copying a portion of an array. * * @since 1.0 */ public final class System { /* Register the natives via the static initializer. * * VM will invoke the initializeSystemClass method to complete * the initialization for this class separated from clinit. * Note that to use properties set by the VM, see the constraints * described in the initializeSystemClass method. */ private static native void registerNatives(); static { registerNatives(); } /** Don't let anyone instantiate this class */ private System() { } /** * The "standard" input stream. This stream is already * open and ready to supply input data. Typically this stream * corresponds to keyboard input or another input source specified by * the host environment or user. */ public static final InputStream in = null; /** * The "standard" output stream. This stream is already * open and ready to accept output data. Typically this stream * corresponds to display output or another output destination * specified by the host environment or user. * <p> * For simple stand-alone Java applications, a typical way to write * a line of output data is: * <blockquote><pre> * System.out.println(data) * </pre></blockquote> * <p> * See the {@code println} methods in class {@code PrintStream}. * * @see java.io.PrintStream#println() * @see java.io.PrintStream#println(boolean) * @see java.io.PrintStream#println(char) * @see java.io.PrintStream#println(char[]) * @see java.io.PrintStream#println(double) * @see java.io.PrintStream#println(float) * @see java.io.PrintStream#println(int) * @see java.io.PrintStream#println(long) * @see java.io.PrintStream#println(java.lang.Object) * @see java.io.PrintStream#println(java.lang.String) */ public static final PrintStream out = null; /** * The "standard" error output stream. This stream is already * open and ready to accept output data. * <p> * Typically this stream corresponds to display output or another * output destination specified by the host environment or user. By * convention, this output stream is used to display error messages * or other information that should come to the immediate attention * of a user even if the principal output stream, the value of the * variable {@code out}, has been redirected to a file or other * destination that is typically not continuously monitored. */ public static final PrintStream err = null; // indicates if a security manager is possible private static final int NEVER = 1; private static final int MAYBE = 2; private static @Stable int allowSecurityManager; // current security manager private static volatile SecurityManager security; // read by VM // return true if a security manager is allowed private static boolean allowSecurityManager() { return (allowSecurityManager != NEVER); } /** * Reassigns the "standard" input stream. * * First, if there is a security manager, its {@code checkPermission} * method is called with a {@code RuntimePermission("setIO")} permission * to see if it's ok to reassign the "standard" input stream. * * @param in the new standard input stream. * * @throws SecurityException * if a security manager exists and its * {@code checkPermission} method doesn't allow * reassigning of the standard input stream. * * @see SecurityManager#checkPermission * @see java.lang.RuntimePermission * * @since 1.1 */ public static void setIn(InputStream in) { checkIO(); setIn0(in); } /** * Reassigns the "standard" output stream. * * First, if there is a security manager, its {@code checkPermission} * method is called with a {@code RuntimePermission("setIO")} permission * to see if it's ok to reassign the "standard" output stream. * * @param out the new standard output stream * * @throws SecurityException * if a security manager exists and its * {@code checkPermission} method doesn't allow * reassigning of the standard output stream. * * @see SecurityManager#checkPermission * @see java.lang.RuntimePermission * * @since 1.1 */ public static void setOut(PrintStream out) { checkIO(); setOut0(out); } /** * Reassigns the "standard" error output stream. * * First, if there is a security manager, its {@code checkPermission} * method is called with a {@code RuntimePermission("setIO")} permission * to see if it's ok to reassign the "standard" error output stream. * * @param err the new standard error output stream. * * @throws SecurityException * if a security manager exists and its * {@code checkPermission} method doesn't allow * reassigning of the standard error output stream. * * @see SecurityManager#checkPermission * @see java.lang.RuntimePermission * * @since 1.1 */ public static void setErr(PrintStream err) { checkIO(); setErr0(err); } private static volatile Console cons; /** * Returns the unique {@link java.io.Console Console} object associated * with the current Java virtual machine, if any. * * @return The system console, if any, otherwise {@code null}. * * @since 1.6 */ public static Console console() { Console c; if ((c = cons) == null) { synchronized (System.class) { if ((c = cons) == null) { cons = c = SharedSecrets.getJavaIOAccess().console(); } } } return c; } /** * Returns the channel inherited from the entity that created this * Java virtual machine. * * This method returns the channel obtained by invoking the * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel * inheritedChannel} method of the system-wide default * {@link java.nio.channels.spi.SelectorProvider} object. * * <p> In addition to the network-oriented channels described in * {@link java.nio.channels.spi.SelectorProvider#inheritedChannel * inheritedChannel}, this method may return other kinds of * channels in the future. * * @return The inherited channel, if any, otherwise {@code null}. * * @throws IOException * If an I/O error occurs * * @throws SecurityException * If a security manager is present and it does not * permit access to the channel. * * @since 1.5 */ public static Channel inheritedChannel() throws IOException { return SelectorProvider.provider().inheritedChannel(); } private static void checkIO() { SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPermission(new RuntimePermission("setIO")); } } private static native void setIn0(InputStream in); private static native void setOut0(PrintStream out); private static native void setErr0(PrintStream err); /** * Sets the system-wide security manager. * * If there is a security manager already installed, this method first * calls the security manager's {@code checkPermission} method * with a {@code RuntimePermission("setSecurityManager")} * permission to ensure it's ok to replace the existing * security manager. * This may result in throwing a {@code SecurityException}. * * <p> Otherwise, the argument is established as the current * security manager. If the argument is {@code null} and no * security manager has been established, then no action is taken and * the method simply returns. * * @implNote In the JDK implementation, if the Java virtual machine is * started with the system property {@code java.security.manager} set to * the special token "{@code disallow}" then the {@code setSecurityManager} * method cannot be used to set a security manager. * * @param sm the security manager or {@code null} * @throws SecurityException * if the security manager has already been set and its {@code * checkPermission} method doesn't allow it to be replaced * @throws UnsupportedOperationException * if {@code sm} is non-null and a security manager is not allowed * to be set dynamically * @see #getSecurityManager * @see SecurityManager#checkPermission * @see java.lang.RuntimePermission */ public static void setSecurityManager(SecurityManager sm) { if (allowSecurityManager()) { if (security == null) { // ensure image reader is initialized Object.class.getResource("java/lang/ANY"); } if (sm != null) { try { // pre-populates the SecurityManager.packageAccess cache // to avoid recursive permission checking issues with custom // SecurityManager implementations sm.checkPackageAccess("java.lang"); } catch (Exception e) { // no-op } } setSecurityManager0(sm); } else { // security manager not allowed if (sm != null) { throw new UnsupportedOperationException("Runtime configured to disallow security manager"); } } } private static synchronized void setSecurityManager0(final SecurityManager s) { SecurityManager sm = getSecurityManager(); if (sm != null) { // ask the currently installed security manager if we // can replace it. sm.checkPermission(new RuntimePermission("setSecurityManager")); } if ((s != null) && (s.getClass().getClassLoader() != null)) { // New security manager class is not on bootstrap classpath. // Force policy to get initialized before we install the new // security manager, in order to prevent infinite loops when // trying to initialize the policy (which usually involves // accessing some security and/or system properties, which in turn // calls the installed security manager's checkPermission method // which will loop infinitely if there is a non-system class // (in this case: the new security manager class) on the stack). AccessController.doPrivileged(new PrivilegedAction<>() { public Object run() { s.getClass().getProtectionDomain().implies(SecurityConstants.ALL_PERMISSION); return null; } }); } security = s; } /** * Gets the system-wide security manager. * * @return if a security manager has already been established for the * current application, then that security manager is returned; * otherwise, {@code null} is returned. * @see #setSecurityManager */ public static SecurityManager getSecurityManager() { if (allowSecurityManager()) { return security; } else { return null; } } /** * Returns the current time in milliseconds. Note that * while the unit of time of the return value is a millisecond, * the granularity of the value depends on the underlying * operating system and may be larger. For example, many * operating systems measure time in units of tens of * milliseconds. * * <p> See the description of the class {@code Date} for * a discussion of slight discrepancies that may arise between * "computer time" and coordinated universal time (UTC). * * @return the difference, measured in milliseconds, between * the current time and midnight, January 1, 1970 UTC. * @see java.util.Date */ @HotSpotIntrinsicCandidate public static native long currentTimeMillis(); /** * Returns the current value of the running Java Virtual Machine's * high-resolution time source, in nanoseconds. * * This method can only be used to measure elapsed time and is * not related to any other notion of system or wall-clock time. * The value returned represents nanoseconds since some fixed but * arbitrary <i>origin</i> time (perhaps in the future, so values * may be negative). The same origin is used by all invocations of * this method in an instance of a Java virtual machine; other * virtual machine instances are likely to use a different origin. * * <p>This method provides nanosecond precision, but not necessarily * nanosecond resolution (that is, how frequently the value changes) * - no guarantees are made except that the resolution is at least as * good as that of {@link #currentTimeMillis()}. * * <p>Differences in successive calls that span greater than * approximately 292 years (2<sup>63</sup> nanoseconds) will not * correctly compute elapsed time due to numerical overflow. * * <p>The values returned by this method become meaningful only when * the difference between two such values, obtained within the same * instance of a Java virtual machine, is computed. * * <p>For example, to measure how long some code takes to execute: * <pre> {@code * long startTime = System.nanoTime(); * // ... the code being measured ... * long elapsedNanos = System.nanoTime() - startTime;}</pre> * * <p>To compare elapsed time against a timeout, use <pre> {@code * if (System.nanoTime() - startTime >= timeoutNanos) ...}</pre> * instead of <pre> {@code * if (System.nanoTime() >= startTime + timeoutNanos) ...}</pre> * because of the possibility of numerical overflow. * * @return the current value of the running Java Virtual Machine's * high-resolution time source, in nanoseconds * @since 1.5 */ @HotSpotIntrinsicCandidate public static native long nanoTime(); /** * Copies an array from the specified source array, beginning at the * specified position, to the specified position of the destination array. * A subsequence of array components are copied from the source * array referenced by {@code src} to the destination array * referenced by {@code dest}. The number of components copied is * equal to the {@code length} argument. The components at * positions {@code srcPos} through * {@code srcPos+length-1} in the source array are copied into * positions {@code destPos} through * {@code destPos+length-1}, respectively, of the destination * array. * <p> * If the {@code src} and {@code dest} arguments refer to the * same array object, then the copying is performed as if the * components at positions {@code srcPos} through * {@code srcPos+length-1} were first copied to a temporary * array with {@code length} components and then the contents of * the temporary array were copied into positions * {@code destPos} through {@code destPos+length-1} of the * destination array. * <p> * If {@code dest} is {@code null}, then a * {@code NullPointerException} is thrown. * <p> * If {@code src} is {@code null}, then a * {@code NullPointerException} is thrown and the destination * array is not modified. * <p> * Otherwise, if any of the following is true, an * {@code ArrayStoreException} is thrown and the destination is * not modified: * <ul> * <li>The {@code src} argument refers to an object that is not an * array. * <li>The {@code dest} argument refers to an object that is not an * array. * <li>The {@code src} argument and {@code dest} argument refer * to arrays whose component types are different primitive types. * <li>The {@code src} argument refers to an array with a primitive * component type and the {@code dest} argument refers to an array * with a reference component type. * <li>The {@code src} argument refers to an array with a reference * component type and the {@code dest} argument refers to an array * with a primitive component type. * </ul> * <p> * Otherwise, if any of the following is true, an * {@code IndexOutOfBoundsException} is * thrown and the destination is not modified: * <ul> * <li>The {@code srcPos} argument is negative. * <li>The {@code destPos} argument is negative. * <li>The {@code length} argument is negative. * <li>{@code srcPos+length} is greater than * {@code src.length}, the length of the source array. * <li>{@code destPos+length} is greater than * {@code dest.length}, the length of the destination array. * </ul> * <p> * Otherwise, if any actual component of the source array from * position {@code srcPos} through * {@code srcPos+length-1} cannot be converted to the component * type of the destination array by assignment conversion, an * {@code ArrayStoreException} is thrown. In this case, let * <b><i>k</i></b> be the smallest nonnegative integer less than * length such that {@code src[srcPos+}<i>k</i>{@code ]} * cannot be converted to the component type of the destination * array; when the exception is thrown, source array components from * positions {@code srcPos} through * {@code srcPos+}<i>k</i>{@code -1} * will already have been copied to destination array positions * {@code destPos} through * {@code destPos+}<i>k</I>{@code -1} and no other * positions of the destination array will have been modified. * (Because of the restrictions already itemized, this * paragraph effectively applies only to the situation where both * arrays have component types that are reference types.) * * @param src the source array. * @param srcPos starting position in the source array. * @param dest the destination array. * @param destPos starting position in the destination data. * @param length the number of array elements to be copied. * @throws IndexOutOfBoundsException if copying would cause * access of data outside array bounds. * @throws ArrayStoreException if an element in the {@code src} * array could not be stored into the {@code dest} array * because of a type mismatch. * @throws NullPointerException if either {@code src} or * {@code dest} is {@code null}. */ @HotSpotIntrinsicCandidate public static native void arraycopy(Object src, int srcPos, Object dest, int destPos, int length); /** * Returns the same hash code for the given object as * would be returned by the default method hashCode(), * whether or not the given object's class overrides * hashCode(). * The hash code for the null reference is zero. * * @param x object for which the hashCode is to be calculated * @return the hashCode * @since 1.1 * @see Object#hashCode * @see java.util.Objects#hashCode(Object) */ @HotSpotIntrinsicCandidate public static native int identityHashCode(Object x); /** * System properties. The following properties are guaranteed to be defined: * <dl> * <dt>java.version <dd>Java version number * <dt>java.version.date <dd>Java version date * <dt>java.vendor <dd>Java vendor specific string * <dt>java.vendor.url <dd>Java vendor URL * <dt>java.vendor.version <dd>Java vendor version * <dt>java.home <dd>Java installation directory * <dt>java.class.version <dd>Java class version number * <dt>java.class.path <dd>Java classpath * <dt>os.name <dd>Operating System Name * <dt>os.arch <dd>Operating System Architecture * <dt>os.version <dd>Operating System Version * <dt>file.separator <dd>File separator ("/" on Unix) * <dt>path.separator <dd>Path separator (":" on Unix) * <dt>line.separator <dd>Line separator ("\n" on Unix) * <dt>user.name <dd>User account name * <dt>user.home <dd>User home directory * <dt>user.dir <dd>User's current working directory * </dl> */ private static Properties props; /** * Determines the current system properties. * * First, if there is a security manager, its * {@code checkPropertiesAccess} method is called with no * arguments. This may result in a security exception. * <p> * The current set of system properties for use by the * {@link #getProperty(String)} method is returned as a * {@code Properties} object. If there is no current set of * system properties, a set of system properties is first created and * initialized. This set of system properties includes a value * for each of the following keys unless the description of the associated * value indicates that the value is optional. * <table class="striped" style="text-align:left"> * <caption style="display:none">Shows property keys and associated values</caption> * <thead> * <tr><th scope="col">Key</th> * <th scope="col">Description of Associated Value</th></tr> * </thead> * <tbody> * <tr><th scope="row">{@systemProperty java.version}</th> * <td>Java Runtime Environment version, which may be interpreted * as a {@link Runtime.Version}</td></tr> * <tr><th scope="row">{@systemProperty java.version.date}</th> * <td>Java Runtime Environment version date, in ISO-8601 YYYY-MM-DD * format, which may be interpreted as a {@link * java.time.LocalDate}</td></tr> * <tr><th scope="row">{@systemProperty java.vendor}</th> * <td>Java Runtime Environment vendor</td></tr> * <tr><th scope="row">{@systemProperty java.vendor.url}</th> * <td>Java vendor URL</td></tr> * <tr><th scope="row">{@systemProperty java.vendor.version}</th> * <td>Java vendor version <em>(optional)</em> </td></tr> * <tr><th scope="row">{@systemProperty java.home}</th> * <td>Java installation directory</td></tr> * <tr><th scope="row">{@systemProperty java.vm.specification.version}</th> * <td>Java Virtual Machine specification version, whose value is the * {@linkplain Runtime.Version#feature feature} element of the * {@linkplain Runtime#version() runtime version}</td></tr> * <tr><th scope="row">{@systemProperty java.vm.specification.vendor}</th> * <td>Java Virtual Machine specification vendor</td></tr> * <tr><th scope="row">{@systemProperty java.vm.specification.name}</th> * <td>Java Virtual Machine specification name</td></tr> * <tr><th scope="row">{@systemProperty java.vm.version}</th> * <td>Java Virtual Machine implementation version which may be * interpreted as a {@link Runtime.Version}</td></tr> * <tr><th scope="row">{@systemProperty java.vm.vendor}</th> * <td>Java Virtual Machine implementation vendor</td></tr> * <tr><th scope="row">{@systemProperty java.vm.name}</th> * <td>Java Virtual Machine implementation name</td></tr> * <tr><th scope="row">{@systemProperty java.specification.version}</th> * <td>Java Runtime Environment specification version, whose value is * the {@linkplain Runtime.Version#feature feature} element of the * {@linkplain Runtime#version() runtime version}</td></tr> * <tr><th scope="row">{@systemProperty java.specification.vendor}</th> * <td>Java Runtime Environment specification vendor</td></tr> * <tr><th scope="row">{@systemProperty java.specification.name}</th> * <td>Java Runtime Environment specification name</td></tr> * <tr><th scope="row">{@systemProperty java.class.version}</th> * <td>Java class format version number</td></tr> * <tr><th scope="row">{@systemProperty java.class.path}</th> * <td>Java class path (refer to * {@link ClassLoader#getSystemClassLoader()} for details)</td></tr> * <tr><th scope="row">{@systemProperty java.library.path}</th> * <td>List of paths to search when loading libraries</td></tr> * <tr><th scope="row">{@systemProperty java.io.tmpdir}</th> * <td>Default temp file path</td></tr> * <tr><th scope="row">{@systemProperty java.compiler}</th> * <td>Name of JIT compiler to use</td></tr> * <tr><th scope="row">{@systemProperty os.name}</th> * <td>Operating system name</td></tr> * <tr><th scope="row">{@systemProperty os.arch}</th> * <td>Operating system architecture</td></tr> * <tr><th scope="row">{@systemProperty os.version}</th> * <td>Operating system version</td></tr> * <tr><th scope="row">{@systemProperty file.separator}</th> * <td>File separator ("/" on UNIX)</td></tr> * <tr><th scope="row">{@systemProperty path.separator}</th> * <td>Path separator (":" on UNIX)</td></tr> * <tr><th scope="row">{@systemProperty line.separator}</th> * <td>Line separator ("\n" on UNIX)</td></tr> * <tr><th scope="row">{@systemProperty user.name}</th> * <td>User's account name</td></tr> * <tr><th scope="row">{@systemProperty user.home}</th> * <td>User's home directory</td></tr> * <tr><th scope="row">{@systemProperty user.dir}</th> * <td>User's current working directory</td></tr> * </tbody> * </table> * <p> * Multiple paths in a system property value are separated by the path * separator character of the platform. * <p> * Note that even if the security manager does not permit the * {@code getProperties} operation, it may choose to permit the * {@link #getProperty(String)} operation. * * @apiNote * <strong>Changing a standard system property may have unpredictable results * unless otherwise specified.</strong> * Property values may be cached during initialization or on first use. * Setting a standard property after initialization using {@link #getProperties()}, * {@link #setProperties(Properties)}, {@link #setProperty(String, String)}, or * {@link #clearProperty(String)} may not have the desired effect. * * @implNote * In addition to the standard system properties, the system * properties may include the following keys: * <table class="striped"> * <caption style="display:none">Shows property keys and associated values</caption> * <thead> * <tr><th scope="col">Key</th> * <th scope="col">Description of Associated Value</th></tr> * </thead> * <tbody> * <tr><th scope="row">{@systemProperty jdk.module.path}</th> * <td>The application module path</td></tr> * <tr><th scope="row">{@systemProperty jdk.module.upgrade.path}</th> * <td>The upgrade module path</td></tr> * <tr><th scope="row">{@systemProperty jdk.module.main}</th> * <td>The module name of the initial/main module</td></tr> * <tr><th scope="row">{@systemProperty jdk.module.main.class}</th> * <td>The main class name of the initial module</td></tr> * </tbody> * </table> * * @return the system properties * @throws SecurityException if a security manager exists and its * {@code checkPropertiesAccess} method doesn't allow access * to the system properties. * @see #setProperties * @see java.lang.SecurityException * @see java.lang.SecurityManager#checkPropertiesAccess() * @see java.util.Properties */ public static Properties getProperties() { SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPropertiesAccess(); } return props; } /** * Returns the system-dependent line separator string. It always * returns the same value - the initial value of the {@linkplain * #getProperty(String) system property} {@code line.separator}. * * <p>On UNIX systems, it returns {@code "\n"}; on Microsoft * Windows systems it returns {@code "\r\n"}. * * @return the system-dependent line separator string * @since 1.7 */ public static String lineSeparator() { return lineSeparator; } private static String lineSeparator; /** * Sets the system properties to the {@code Properties} argument. * * First, if there is a security manager, its * {@code checkPropertiesAccess} method is called with no * arguments. This may result in a security exception. * <p> * The argument becomes the current set of system properties for use * by the {@link #getProperty(String)} method. If the argument is * {@code null}, then the current set of system properties is * forgotten. * * @apiNote * <strong>Changing a standard system property may have unpredictable results * unless otherwise specified</strong>. * See {@linkplain #getProperties getProperties} for details. * * @param props the new system properties. * @throws SecurityException if a security manager exists and its * {@code checkPropertiesAccess} method doesn't allow access * to the system properties. * @see #getProperties * @see java.util.Properties * @see java.lang.SecurityException * @see java.lang.SecurityManager#checkPropertiesAccess() */ public static void setProperties(Properties props) { SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPropertiesAccess(); } if (props == null) { Map<String, String> tempProps = SystemProps.initProperties(); VersionProps.init(tempProps); props = createProperties(tempProps); } System.props = props; } /** * Gets the system property indicated by the specified key. * * First, if there is a security manager, its * {@code checkPropertyAccess} method is called with the key as * its argument. This may result in a SecurityException. * <p> * If there is no current set of system properties, a set of system * properties is first created and initialized in the same manner as * for the {@code getProperties} method. * * @apiNote * <strong>Changing a standard system property may have unpredictable results * unless otherwise specified</strong>. * See {@linkplain #getProperties getProperties} for details. * * @param key the name of the system property. * @return the string value of the system property, * or {@code null} if there is no property with that key. * * @throws SecurityException if a security manager exists and its * {@code checkPropertyAccess} method doesn't allow * access to the specified system property. * @throws NullPointerException if {@code key} is {@code null}. * @throws IllegalArgumentException if {@code key} is empty. * @see #setProperty * @see java.lang.SecurityException * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String) * @see java.lang.System#getProperties() */ public static String getProperty(String key) { checkKey(key); SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPropertyAccess(key); } return props.getProperty(key); } /** * Gets the system property indicated by the specified key. * * First, if there is a security manager, its * {@code checkPropertyAccess} method is called with the * {@code key} as its argument. * <p> * If there is no current set of system properties, a set of system * properties is first created and initialized in the same manner as * for the {@code getProperties} method. * * @param key the name of the system property. * @param def a default value. * @return the string value of the system property, * or the default value if there is no property with that key. * * @throws SecurityException if a security manager exists and its * {@code checkPropertyAccess} method doesn't allow * access to the specified system property. * @throws NullPointerException if {@code key} is {@code null}. * @throws IllegalArgumentException if {@code key} is empty. * @see #setProperty * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String) * @see java.lang.System#getProperties() */ public static String getProperty(String key, String def) { checkKey(key); SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPropertyAccess(key); } return props.getProperty(key, def); } /** * Sets the system property indicated by the specified key. * * First, if a security manager exists, its * {@code SecurityManager.checkPermission} method * is called with a {@code PropertyPermission(key, "write")} * permission. This may result in a SecurityException being thrown. * If no exception is thrown, the specified property is set to the given * value. * * @apiNote * <strong>Changing a standard system property may have unpredictable results * unless otherwise specified</strong>. * See {@linkplain #getProperties getProperties} for details. * * @param key the name of the system property. * @param value the value of the system property. * @return the previous value of the system property, * or {@code null} if it did not have one. * * @throws SecurityException if a security manager exists and its * {@code checkPermission} method doesn't allow * setting of the specified property. * @throws NullPointerException if {@code key} or * {@code value} is {@code null}. * @throws IllegalArgumentException if {@code key} is empty. * @see #getProperty * @see java.lang.System#getProperty(java.lang.String) * @see java.lang.System#getProperty(java.lang.String, java.lang.String) * @see java.util.PropertyPermission * @see SecurityManager#checkPermission * @since 1.2 */ public static String setProperty(String key, String value) { checkKey(key); SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPermission(new PropertyPermission(key, SecurityConstants.PROPERTY_WRITE_ACTION)); } return (String) props.setProperty(key, value); } /** * Removes the system property indicated by the specified key. * * First, if a security manager exists, its * {@code SecurityManager.checkPermission} method * is called with a {@code PropertyPermission(key, "write")} * permission. This may result in a SecurityException being thrown. * If no exception is thrown, the specified property is removed. * * @apiNote * <strong>Changing a standard system property may have unpredictable results * unless otherwise specified</strong>. * See {@linkplain #getProperties getProperties} method for details. * * @param key the name of the system property to be removed. * @return the previous string value of the system property, * or {@code null} if there was no property with that key. * * @throws SecurityException if a security manager exists and its * {@code checkPropertyAccess} method doesn't allow * access to the specified system property. * @throws NullPointerException if {@code key} is {@code null}. * @throws IllegalArgumentException if {@code key} is empty. * @see #getProperty * @see #setProperty * @see java.util.Properties * @see java.lang.SecurityException * @see java.lang.SecurityManager#checkPropertiesAccess() * @since 1.5 */ public static String clearProperty(String key) { checkKey(key); SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPermission(new PropertyPermission(key, "write")); } return (String) props.remove(key); } private static void checkKey(String key) { if (key == null) { throw new NullPointerException("key can't be null"); } if (key.isEmpty()) { throw new IllegalArgumentException("key can't be empty"); } } /** * Gets the value of the specified environment variable. An * environment variable is a system-dependent external named * value. * * <p>If a security manager exists, its * {@link SecurityManager#checkPermission checkPermission} * method is called with a * {@link RuntimePermission RuntimePermission("getenv."+name)} * permission. This may result in a {@link SecurityException} * being thrown. If no exception is thrown the value of the * variable {@code name} is returned. * * <p><a id="EnvironmentVSSystemProperties"><i>System * properties</i> and <i>environment variables</i></a> are both * conceptually mappings between names and values. Both * mechanisms can be used to pass user-defined information to a * Java process. Environment variables have a more global effect, * because they are visible to all descendants of the process * which defines them, not just the immediate Java subprocess. * They can have subtly different semantics, such as case * insensitivity, on different operating systems. For these * reasons, environment variables are more likely to have * unintended side effects. It is best to use system properties * where possible. Environment variables should be used when a * global effect is desired, or when an external system interface * requires an environment variable (such as {@code PATH}). * * <p>On UNIX systems the alphabetic case of {@code name} is * typically significant, while on Microsoft Windows systems it is * typically not. For example, the expression * {@code System.getenv("FOO").equals(System.getenv("foo"))} * is likely to be true on Microsoft Windows. * * @param name the name of the environment variable * @return the string value of the variable, or {@code null} * if the variable is not defined in the system environment * @throws NullPointerException if {@code name} is {@code null} * @throws SecurityException * if a security manager exists and its * {@link SecurityManager#checkPermission checkPermission} * method doesn't allow access to the environment variable * {@code name} * @see #getenv() * @see ProcessBuilder#environment() */ public static String getenv(String name) { SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPermission(new RuntimePermission("getenv." + name)); } return ProcessEnvironment.getenv(name); } /** * Returns an unmodifiable string map view of the current system environment. * The environment is a system-dependent mapping from names to * values which is passed from parent to child processes. * * <p>If the system does not support environment variables, an * empty map is returned. * * <p>The returned map will never contain null keys or values. * Attempting to query the presence of a null key or value will * throw a {@link NullPointerException}. Attempting to query * the presence of a key or value which is not of type * {@link String} will throw a {@link ClassCastException}. * * <p>The returned map and its collection views may not obey the * general contract of the {@link Object#equals} and * {@link Object#hashCode} methods. * * <p>The returned map is typically case-sensitive on all platforms. * * <p>If a security manager exists, its * {@link SecurityManager#checkPermission checkPermission} * method is called with a * {@link RuntimePermission RuntimePermission("getenv.*")} permission. * This may result in a {@link SecurityException} being thrown. * * <p>When passing information to a Java subprocess, * <a href=#EnvironmentVSSystemProperties>system properties</a> * are generally preferred over environment variables. * * @return the environment as a map of variable names to values * @throws SecurityException * if a security manager exists and its * {@link SecurityManager#checkPermission checkPermission} * method doesn't allow access to the process environment * @see #getenv(String) * @see ProcessBuilder#environment() * @since 1.5 */ public static java.util.Map<String, String> getenv() { SecurityManager sm = getSecurityManager(); if (sm != null) { sm.checkPermission(new RuntimePermission("getenv.*")); } return ProcessEnvironment.getenv(); } /** * {@code System.Logger} instances log messages that will be * routed to the underlying logging framework the {@link System.LoggerFinder * LoggerFinder} uses. * * {@code System.Logger} instances are typically obtained from * the {@link java.lang.System System} class, by calling * {@link java.lang.System#getLogger(java.lang.String) System.getLogger(loggerName)} * or {@link java.lang.System#getLogger(java.lang.String, java.util.ResourceBundle) * System.getLogger(loggerName, bundle)}. * * @see java.lang.System#getLogger(java.lang.String) * @see java.lang.System#getLogger(java.lang.String, java.util.ResourceBundle) * @see java.lang.System.LoggerFinder * * @since 9 */ public interface Logger { /** * System {@linkplain Logger loggers} levels. * * A level has a {@linkplain #getName() name} and {@linkplain * #getSeverity() severity}. * Level values are {@link #ALL}, {@link #TRACE}, {@link #DEBUG}, * {@link #INFO}, {@link #WARNING}, {@link #ERROR}, {@link #OFF}, * by order of increasing severity. * <br> * {@link #ALL} and {@link #OFF} * are simple markers with severities mapped respectively to * {@link java.lang.Integer#MIN_VALUE Integer.MIN_VALUE} and * {@link java.lang.Integer#MAX_VALUE Integer.MAX_VALUE}. * <p> * <b>Severity values and Mapping to {@code java.util.logging.Level}.</b> * <p> * {@linkplain System.Logger.Level System logger levels} are mapped to * {@linkplain java.util.logging.Level java.util.logging levels} * of corresponding severity. * <br>The mapping is as follows: * <br><br> * <table class="striped"> * <caption>System.Logger Severity Level Mapping</caption> * <thead> * <tr><th scope="col">System.Logger Levels</th> * <th scope="col">java.util.logging Levels</th> * </thead> * <tbody> * <tr><th scope="row">{@link Logger.Level#ALL ALL}</th> * <td>{@link java.util.logging.Level#ALL ALL}</td> * <tr><th scope="row">{@link Logger.Level#TRACE TRACE}</th> * <td>{@link java.util.logging.Level#FINER FINER}</td> * <tr><th scope="row">{@link Logger.Level#DEBUG DEBUG}</th> * <td>{@link java.util.logging.Level#FINE FINE}</td> * <tr><th scope="row">{@link Logger.Level#INFO INFO}</th> * <td>{@link java.util.logging.Level#INFO INFO}</td> * <tr><th scope="row">{@link Logger.Level#WARNING WARNING}</th> * <td>{@link java.util.logging.Level#WARNING WARNING}</td> * <tr><th scope="row">{@link Logger.Level#ERROR ERROR}</th> * <td>{@link java.util.logging.Level#SEVERE SEVERE}</td> * <tr><th scope="row">{@link Logger.Level#OFF OFF}</th> * <td>{@link java.util.logging.Level#OFF OFF}</td> * </tbody> * </table> * * @since 9 * * @see java.lang.System.LoggerFinder * @see java.lang.System.Logger */ public enum Level { // for convenience, we're reusing java.util.logging.Level int values // the mapping logic in sun.util.logging.PlatformLogger depends // on this. /** * A marker to indicate that all levels are enabled. * This level {@linkplain #getSeverity() severity} is * {@link Integer#MIN_VALUE}. */ ALL(Integer.MIN_VALUE), // typically mapped to/from j.u.l.Level.ALL /** * {@code TRACE} level: usually used to log diagnostic information. * This level {@linkplain #getSeverity() severity} is * {@code 400}. */ TRACE(400), // typically mapped to/from j.u.l.Level.FINER /** * {@code DEBUG} level: usually used to log debug information traces. * This level {@linkplain #getSeverity() severity} is * {@code 500}. */ DEBUG(500), // typically mapped to/from j.u.l.Level.FINEST/FINE/CONFIG /** * {@code INFO} level: usually used to log information messages. * This level {@linkplain #getSeverity() severity} is * {@code 800}. */ INFO(800), // typically mapped to/from j.u.l.Level.INFO /** * {@code WARNING} level: usually used to log warning messages. * This level {@linkplain #getSeverity() severity} is * {@code 900}. */ WARNING(900), // typically mapped to/from j.u.l.Level.WARNING /** * {@code ERROR} level: usually used to log error messages. * This level {@linkplain #getSeverity() severity} is * {@code 1000}. */ ERROR(1000), // typically mapped to/from j.u.l.Level.SEVERE /** * A marker to indicate that all levels are disabled. * This level {@linkplain #getSeverity() severity} is * {@link Integer#MAX_VALUE}. */ OFF(Integer.MAX_VALUE); // typically mapped to/from j.u.l.Level.OFF private final int severity; private Level(int severity) { this.severity = severity; } /** * Returns the name of this level. * @return this level {@linkplain #name()}. */ public final String getName() { return name(); } /** * Returns the severity of this level. * A higher severity means a more severe condition. * @return this level severity. */ public final int getSeverity() { return severity; } } /** * Returns the name of this logger. * * @return the logger name. */ public String getName(); /** * Checks if a message of the given level would be logged by * this logger. * * @param level the log message level. * @return {@code true} if the given log message level is currently * being logged. * * @throws NullPointerException if {@code level} is {@code null}. */ public boolean isLoggable(Level level); /** * Logs a message. * * @implSpec The default implementation for this method calls * {@code this.log(level, (ResourceBundle)null, msg, (Object[])null);} * * @param level the log message level. * @param msg the string message (or a key in the message catalog, if * this logger is a {@link * LoggerFinder#getLocalizedLogger(java.lang.String, * java.util.ResourceBundle, java.lang.Module) localized logger}); * can be {@code null}. * * @throws NullPointerException if {@code level} is {@code null}. */ public default void log(Level level, String msg) { log(level, (ResourceBundle) null, msg, (Object[]) null); } /** * Logs a lazily supplied message. * * If the logger is currently enabled for the given log message level * then a message is logged that is the result produced by the * given supplier function. Otherwise, the supplier is not operated on. * * @implSpec When logging is enabled for the given level, the default * implementation for this method calls * {@code this.log(level, (ResourceBundle)null, msgSupplier.get(), (Object[])null);} * * @param level the log message level. * @param msgSupplier a supplier function that produces a message. * * @throws NullPointerException if {@code level} is {@code null}, * or {@code msgSupplier} is {@code null}. */ public default void log(Level level, Supplier<String> msgSupplier) { Objects.requireNonNull(msgSupplier); if (isLoggable(Objects.requireNonNull(level))) { log(level, (ResourceBundle) null, msgSupplier.get(), (Object[]) null); } } /** * Logs a message produced from the given object. * * If the logger is currently enabled for the given log message level then * a message is logged that, by default, is the result produced from * calling toString on the given object. * Otherwise, the object is not operated on. * * @implSpec When logging is enabled for the given level, the default * implementation for this method calls * {@code this.log(level, (ResourceBundle)null, obj.toString(), (Object[])null);} * * @param level the log message level. * @param obj the object to log. * * @throws NullPointerException if {@code level} is {@code null}, or * {@code obj} is {@code null}. */ public default void log(Level level, Object obj) { Objects.requireNonNull(obj); if (isLoggable(Objects.requireNonNull(level))) { this.log(level, (ResourceBundle) null, obj.toString(), (Object[]) null); } } /** * Logs a message associated with a given throwable. * * @implSpec The default implementation for this method calls * {@code this.log(level, (ResourceBundle)null, msg, thrown);} * * @param level the log message level. * @param msg the string message (or a key in the message catalog, if * this logger is a {@link * LoggerFinder#getLocalizedLogger(java.lang.String, * java.util.ResourceBundle, java.lang.Module) localized logger}); * can be {@code null}. * @param thrown a {@code Throwable} associated with the log message; * can be {@code null}. * * @throws NullPointerException if {@code level} is {@code null}. */ public default void log(Level level, String msg, Throwable thrown) { this.log(level, null, msg, thrown); } /** * Logs a lazily supplied message associated with a given throwable. * * If the logger is currently enabled for the given log message level * then a message is logged that is the result produced by the * given supplier function. Otherwise, the supplier is not operated on. * * @implSpec When logging is enabled for the given level, the default * implementation for this method calls * {@code this.log(level, (ResourceBundle)null, msgSupplier.get(), thrown);} * * @param level one of the log message level identifiers. * @param msgSupplier a supplier function that produces a message. * @param thrown a {@code Throwable} associated with log message; * can be {@code null}. * * @throws NullPointerException if {@code level} is {@code null}, or * {@code msgSupplier} is {@code null}. */ public default void log(Level level, Supplier<String> msgSupplier, Throwable thrown) { Objects.requireNonNull(msgSupplier); if (isLoggable(Objects.requireNonNull(level))) { this.log(level, null, msgSupplier.get(), thrown); } } /** * Logs a message with an optional list of parameters. * * @implSpec The default implementation for this method calls * {@code this.log(level, (ResourceBundle)null, format, params);} * * @param level one of the log message level identifiers. * @param format the string message format in {@link * java.text.MessageFormat} format, (or a key in the message * catalog, if this logger is a {@link * LoggerFinder#getLocalizedLogger(java.lang.String, * java.util.ResourceBundle, java.lang.Module) localized logger}); * can be {@code null}. * @param params an optional list of parameters to the message (may be * none). * * @throws NullPointerException if {@code level} is {@code null}. */ public default void log(Level level, String format, Object... params) { this.log(level, null, format, params); } /** * Logs a localized message associated with a given throwable. * * If the given resource bundle is non-{@code null}, the {@code msg} * string is localized using the given resource bundle. * Otherwise the {@code msg} string is not localized. * * @param level the log message level. * @param bundle a resource bundle to localize {@code msg}; can be * {@code null}. * @param msg the string message (or a key in the message catalog, * if {@code bundle} is not {@code null}); can be {@code null}. * @param thrown a {@code Throwable} associated with the log message; * can be {@code null}. * * @throws NullPointerException if {@code level} is {@code null}. */ public void log(Level level, ResourceBundle bundle, String msg, Throwable thrown); /** * Logs a message with resource bundle and an optional list of * parameters. * * If the given resource bundle is non-{@code null}, the {@code format} * string is localized using the given resource bundle. * Otherwise the {@code format} string is not localized. * * @param level the log message level. * @param bundle a resource bundle to localize {@code format}; can be * {@code null}. * @param format the string message format in {@link * java.text.MessageFormat} format, (or a key in the message * catalog if {@code bundle} is not {@code null}); can be {@code null}. * @param params an optional list of parameters to the message (may be * none). * * @throws NullPointerException if {@code level} is {@code null}. */ public void log(Level level, ResourceBundle bundle, String format, Object... params); } /** * The {@code LoggerFinder} service is responsible for creating, managing, * and configuring loggers to the underlying framework it uses. * * A logger finder is a concrete implementation of this class that has a * zero-argument constructor and implements the abstract methods defined * by this class. * The loggers returned from a logger finder are capable of routing log * messages to the logging backend this provider supports. * A given invocation of the Java Runtime maintains a single * system-wide LoggerFinder instance that is loaded as follows: * <ul> * <li>First it finds any custom {@code LoggerFinder} provider * using the {@link java.util.ServiceLoader} facility with the * {@linkplain ClassLoader#getSystemClassLoader() system class * loader}.</li> * <li>If no {@code LoggerFinder} provider is found, the system default * {@code LoggerFinder} implementation will be used.</li> * </ul> * <p> * An application can replace the logging backend * <i>even when the java.logging module is present</i>, by simply providing * and declaring an implementation of the {@link LoggerFinder} service. * <p> * <b>Default Implementation</b> * <p> * The system default {@code LoggerFinder} implementation uses * {@code java.util.logging} as the backend framework when the * {@code java.logging} module is present. * It returns a {@linkplain System.Logger logger} instance * that will route log messages to a {@link java.util.logging.Logger * java.util.logging.Logger}. Otherwise, if {@code java.logging} is not * present, the default implementation will return a simple logger * instance that will route log messages of {@code INFO} level and above to * the console ({@code System.err}). * <p> * <b>Logging Configuration</b> * <p> * {@linkplain Logger Logger} instances obtained from the * {@code LoggerFinder} factory methods are not directly configurable by * the application. Configuration is the responsibility of the underlying * logging backend, and usually requires using APIs specific to that backend. * <p>For the default {@code LoggerFinder} implementation * using {@code java.util.logging} as its backend, refer to * {@link java.util.logging java.util.logging} for logging configuration. * For the default {@code LoggerFinder} implementation returning simple loggers * when the {@code java.logging} module is absent, the configuration * is implementation dependent. * <p> * Usually an application that uses a logging framework will log messages * through a logger facade defined (or supported) by that framework. * Applications that wish to use an external framework should log * through the facade associated with that framework. * <p> * A system class that needs to log messages will typically obtain * a {@link System.Logger} instance to route messages to the logging * framework selected by the application. * <p> * Libraries and classes that only need loggers to produce log messages * should not attempt to configure loggers by themselves, as that * would make them dependent from a specific implementation of the * {@code LoggerFinder} service. * <p> * In addition, when a security manager is present, loggers provided to * system classes should not be directly configurable through the logging * backend without requiring permissions. * <br> * It is the responsibility of the provider of * the concrete {@code LoggerFinder} implementation to ensure that * these loggers are not configured by untrusted code without proper * permission checks, as configuration performed on such loggers usually * affects all applications in the same Java Runtime. * <p> * <b>Message Levels and Mapping to backend levels</b> * <p> * A logger finder is responsible for mapping from a {@code * System.Logger.Level} to a level supported by the logging backend it uses. * <br>The default LoggerFinder using {@code java.util.logging} as the backend * maps {@code System.Logger} levels to * {@linkplain java.util.logging.Level java.util.logging} levels * of corresponding severity - as described in {@link Logger.Level * Logger.Level}. * * @see java.lang.System * @see java.lang.System.Logger * * @since 9 */ public static abstract class LoggerFinder { /** * The {@code RuntimePermission("loggerFinder")} is * necessary to subclass and instantiate the {@code LoggerFinder} class, * as well as to obtain loggers from an instance of that class. */ static final RuntimePermission LOGGERFINDER_PERMISSION = new RuntimePermission("loggerFinder"); /** * Creates a new instance of {@code LoggerFinder}. * * @implNote It is recommended that a {@code LoggerFinder} service * implementation does not perform any heavy initialization in its * constructor, in order to avoid possible risks of deadlock or class * loading cycles during the instantiation of the service provider. * * @throws SecurityException if a security manager is present and its * {@code checkPermission} method doesn't allow the * {@code RuntimePermission("loggerFinder")}. */ protected LoggerFinder() { this(checkPermission()); } private LoggerFinder(Void unused) { // nothing to do. } private static Void checkPermission() { final SecurityManager sm = System.getSecurityManager(); if (sm != null) { sm.checkPermission(LOGGERFINDER_PERMISSION); } return null; } /** * Returns an instance of {@link Logger Logger} * for the given {@code module}. * * @param name the name of the logger. * @param module the module for which the logger is being requested. * * @return a {@link Logger logger} suitable for use within the given * module. * @throws NullPointerException if {@code name} is {@code null} or * {@code module} is {@code null}. * @throws SecurityException if a security manager is present and its * {@code checkPermission} method doesn't allow the * {@code RuntimePermission("loggerFinder")}. */ public abstract Logger getLogger(String name, Module module); /** * Returns a localizable instance of {@link Logger Logger} * for the given {@code module}. * The returned logger will use the provided resource bundle for * message localization. * * @implSpec By default, this method calls {@link * #getLogger(java.lang.String, java.lang.Module) * this.getLogger(name, module)} to obtain a logger, then wraps that * logger in a {@link Logger} instance where all methods that do not * take a {@link ResourceBundle} as parameter are redirected to one * which does - passing the given {@code bundle} for * localization. So for instance, a call to {@link * Logger#log(Logger.Level, String) Logger.log(Level.INFO, msg)} * will end up as a call to {@link * Logger#log(Logger.Level, ResourceBundle, String, Object...) * Logger.log(Level.INFO, bundle, msg, (Object[])null)} on the wrapped * logger instance. * Note however that by default, string messages returned by {@link * java.util.function.Supplier Supplier<String>} will not be * localized, as it is assumed that such strings are messages which are * already constructed, rather than keys in a resource bundle. * <p> * An implementation of {@code LoggerFinder} may override this method, * for example, when the underlying logging backend provides its own * mechanism for localizing log messages, then such a * {@code LoggerFinder} would be free to return a logger * that makes direct use of the mechanism provided by the backend. * * @param name the name of the logger. * @param bundle a resource bundle; can be {@code null}. * @param module the module for which the logger is being requested. * @return an instance of {@link Logger Logger} which will use the * provided resource bundle for message localization. * * @throws NullPointerException if {@code name} is {@code null} or * {@code module} is {@code null}. * @throws SecurityException if a security manager is present and its * {@code checkPermission} method doesn't allow the * {@code RuntimePermission("loggerFinder")}. */ public Logger getLocalizedLogger(String name, ResourceBundle bundle, Module module) { return new LocalizedLoggerWrapper<>(getLogger(name, module), bundle); } /** * Returns the {@code LoggerFinder} instance. There is one * single system-wide {@code LoggerFinder} instance in * the Java Runtime. See the class specification of how the * {@link LoggerFinder LoggerFinder} implementation is located and * loaded. * @return the {@link LoggerFinder LoggerFinder} instance. * @throws SecurityException if a security manager is present and its * {@code checkPermission} method doesn't allow the * {@code RuntimePermission("loggerFinder")}. */ public static LoggerFinder getLoggerFinder() { final SecurityManager sm = System.getSecurityManager(); if (sm != null) { sm.checkPermission(LOGGERFINDER_PERMISSION); } return accessProvider(); } private static volatile LoggerFinder service; static LoggerFinder accessProvider() { // We do not need to synchronize: LoggerFinderLoader will // always return the same instance, so if we don't have it, // just fetch it again. if (service == null) { PrivilegedAction<LoggerFinder> pa = () -> LoggerFinderLoader.getLoggerFinder(); service = AccessController.doPrivileged(pa, null, LOGGERFINDER_PERMISSION); } return service; } } /** * Returns an instance of {@link Logger Logger} for the caller's * use. * * @implSpec * Instances returned by this method route messages to loggers * obtained by calling {@link LoggerFinder#getLogger(java.lang.String, * java.lang.Module) LoggerFinder.getLogger(name, module)}, where * {@code module} is the caller's module. * In cases where {@code System.getLogger} is called from a context where * there is no caller frame on the stack (e.g when called directly * from a JNI attached thread), {@code IllegalCallerException} is thrown. * To obtain a logger in such a context, use an auxiliary class that will * implicitly be identified as the caller, or use the system {@link * LoggerFinder#getLoggerFinder() LoggerFinder} to obtain a logger instead. * Note that doing the latter may eagerly initialize the underlying * logging system. * * @apiNote * This method may defer calling the {@link * LoggerFinder#getLogger(java.lang.String, java.lang.Module) * LoggerFinder.getLogger} method to create an actual logger supplied by * the logging backend, for instance, to allow loggers to be obtained during * the system initialization time. * * @param name the name of the logger. * @return an instance of {@link Logger} that can be used by the calling * class. * @throws NullPointerException if {@code name} is {@code null}. * @throws IllegalCallerException if there is no Java caller frame on the * stack. * * @since 9 */ @CallerSensitive public static Logger getLogger(String name) { Objects.requireNonNull(name); final Class<?> caller = Reflection.getCallerClass(); if (caller == null) { throw new IllegalCallerException("no caller frame"); } return LazyLoggers.getLogger(name, caller.getModule()); } /** * Returns a localizable instance of {@link Logger * Logger} for the caller's use. * The returned logger will use the provided resource bundle for message * localization. * * @implSpec * The returned logger will perform message localization as specified * by {@link LoggerFinder#getLocalizedLogger(java.lang.String, * java.util.ResourceBundle, java.lang.Module) * LoggerFinder.getLocalizedLogger(name, bundle, module)}, where * {@code module} is the caller's module. * In cases where {@code System.getLogger} is called from a context where * there is no caller frame on the stack (e.g when called directly * from a JNI attached thread), {@code IllegalCallerException} is thrown. * To obtain a logger in such a context, use an auxiliary class that * will implicitly be identified as the caller, or use the system {@link * LoggerFinder#getLoggerFinder() LoggerFinder} to obtain a logger instead. * Note that doing the latter may eagerly initialize the underlying * logging system. * * @apiNote * This method is intended to be used after the system is fully initialized. * This method may trigger the immediate loading and initialization * of the {@link LoggerFinder} service, which may cause issues if the * Java Runtime is not ready to initialize the concrete service * implementation yet. * System classes which may be loaded early in the boot sequence and * need to log localized messages should create a logger using * {@link #getLogger(java.lang.String)} and then use the log methods that * take a resource bundle as parameter. * * @param name the name of the logger. * @param bundle a resource bundle. * @return an instance of {@link Logger} which will use the provided * resource bundle for message localization. * @throws NullPointerException if {@code name} is {@code null} or * {@code bundle} is {@code null}. * @throws IllegalCallerException if there is no Java caller frame on the * stack. * * @since 9 */ @CallerSensitive public static Logger getLogger(String name, ResourceBundle bundle) { final ResourceBundle rb = Objects.requireNonNull(bundle); Objects.requireNonNull(name); final Class<?> caller = Reflection.getCallerClass(); if (caller == null) { throw new IllegalCallerException("no caller frame"); } final SecurityManager sm = System.getSecurityManager(); // We don't use LazyLoggers if a resource bundle is specified. // Bootstrap sensitive classes in the JDK do not use resource bundles // when logging. This could be revisited later, if it needs to. if (sm != null) { final PrivilegedAction<Logger> pa = () -> LoggerFinder.accessProvider().getLocalizedLogger(name, rb, caller.getModule()); return AccessController.doPrivileged(pa, null, LoggerFinder.LOGGERFINDER_PERMISSION); } return LoggerFinder.accessProvider().getLocalizedLogger(name, rb, caller.getModule()); } /** * Terminates the currently running Java Virtual Machine. The * argument serves as a status code; by convention, a nonzero status * code indicates abnormal termination. * <p> * This method calls the {@code exit} method in class * {@code Runtime}. This method never returns normally. * <p> * The call {@code System.exit(n)} is effectively equivalent to * the call: * <blockquote><pre> * Runtime.getRuntime().exit(n) * </pre></blockquote> * * @param status exit status. * @throws SecurityException * if a security manager exists and its {@code checkExit} * method doesn't allow exit with the specified status. * @see java.lang.Runtime#exit(int) */ public static void exit(int status) { Runtime.getRuntime().exit(status); } /** * Runs the garbage collector in the Java Virtual Machine. * <p> * Calling the {@code gc} method suggests that the Java Virtual Machine * expend effort toward recycling unused objects in order to * make the memory they currently occupy available for reuse * by the Java Virtual Machine. * When control returns from the method call, the Java Virtual Machine * has made a best effort to reclaim space from all unused objects. * There is no guarantee that this effort will recycle any particular * number of unused objects, reclaim any particular amount of space, or * complete at any particular time, if at all, before the method returns or ever. * <p> * The call {@code System.gc()} is effectively equivalent to the * call: * <blockquote><pre> * Runtime.getRuntime().gc() * </pre></blockquote> * * @see java.lang.Runtime#gc() */ public static void gc() { Runtime.getRuntime().gc(); } /** * Runs the finalization methods of any objects pending finalization. * * Calling this method suggests that the Java Virtual Machine expend * effort toward running the {@code finalize} methods of objects * that have been found to be discarded but whose {@code finalize} * methods have not yet been run. When control returns from the * method call, the Java Virtual Machine has made a best effort to * complete all outstanding finalizations. * <p> * The call {@code System.runFinalization()} is effectively * equivalent to the call: * <blockquote><pre> * Runtime.getRuntime().runFinalization() * </pre></blockquote> * * @see java.lang.Runtime#runFinalization() */ public static void runFinalization() { Runtime.getRuntime().runFinalization(); } /** * Loads the native library specified by the filename argument. The filename * argument must be an absolute path name. * * If the filename argument, when stripped of any platform-specific library * prefix, path, and file extension, indicates a library whose name is, * for example, L, and a native library called L is statically linked * with the VM, then the JNI_OnLoad_L function exported by the library * is invoked rather than attempting to load a dynamic library. * A filename matching the argument does not have to exist in the * file system. * See the <a href="{@docRoot}/../specs/jni/index.html"> JNI Specification</a> * for more details. * * Otherwise, the filename argument is mapped to a native library image in * an implementation-dependent manner. * * <p> * The call {@code System.load(name)} is effectively equivalent * to the call: * <blockquote><pre> * Runtime.getRuntime().load(name) * </pre></blockquote> * * @param filename the file to load. * @throws SecurityException if a security manager exists and its * {@code checkLink} method doesn't allow * loading of the specified dynamic library * @throws UnsatisfiedLinkError if either the filename is not an * absolute path name, the native library is not statically * linked with the VM, or the library cannot be mapped to * a native library image by the host system. * @throws NullPointerException if {@code filename} is {@code null} * @see java.lang.Runtime#load(java.lang.String) * @see java.lang.SecurityManager#checkLink(java.lang.String) */ @CallerSensitive public static void load(String filename) { Runtime.getRuntime().load0(Reflection.getCallerClass(), filename); } /** * Loads the native library specified by the {@code libname} * argument. The {@code libname} argument must not contain any platform * specific prefix, file extension or path. If a native library * called {@code libname} is statically linked with the VM, then the * JNI_OnLoad_{@code libname} function exported by the library is invoked. * See the <a href="{@docRoot}/../specs/jni/index.html"> JNI Specification</a> * for more details. * * Otherwise, the libname argument is loaded from a system library * location and mapped to a native library image in an implementation- * dependent manner. * <p> * The call {@code System.loadLibrary(name)} is effectively * equivalent to the call * <blockquote><pre> * Runtime.getRuntime().loadLibrary(name) * </pre></blockquote> * * @param libname the name of the library. * @throws SecurityException if a security manager exists and its * {@code checkLink} method doesn't allow * loading of the specified dynamic library * @throws UnsatisfiedLinkError if either the libname argument * contains a file path, the native library is not statically * linked with the VM, or the library cannot be mapped to a * native library image by the host system. * @throws NullPointerException if {@code libname} is {@code null} * @see java.lang.Runtime#loadLibrary(java.lang.String) * @see java.lang.SecurityManager#checkLink(java.lang.String) */ @CallerSensitive public static void loadLibrary(String libname) { Runtime.getRuntime().loadLibrary0(Reflection.getCallerClass(), libname); } /** * Maps a library name into a platform-specific string representing * a native library. * * @param libname the name of the library. * @return a platform-dependent native library name. * @throws NullPointerException if {@code libname} is {@code null} * @see java.lang.System#loadLibrary(java.lang.String) * @see java.lang.ClassLoader#findLibrary(java.lang.String) * @since 1.2 */ public static native String mapLibraryName(String libname); /** * Create PrintStream for stdout/err based on encoding. */ private static PrintStream newPrintStream(FileOutputStream fos, String enc) { if (enc != null) { try { return new PrintStream(new BufferedOutputStream(fos, 128), true, enc); } catch (UnsupportedEncodingException uee) { } } return new PrintStream(new BufferedOutputStream(fos, 128), true); } /** * Logs an exception/error at initialization time to stdout or stderr. * * @param printToStderr to print to stderr rather than stdout * @param printStackTrace to print the stack trace * @param msg the message to print before the exception, can be {@code null} * @param e the exception or error */ private static void logInitException(boolean printToStderr, boolean printStackTrace, String msg, Throwable e) { if (VM.initLevel() < 1) { throw new InternalError("system classes not initialized"); } PrintStream log = (printToStderr) ? err : out; if (msg != null) { log.println(msg); } if (printStackTrace) { e.printStackTrace(log); } else { log.println(e); for (Throwable suppressed : e.getSuppressed()) { log.println("Suppressed: " + suppressed); } Throwable cause = e.getCause(); if (cause != null) { log.println("Caused by: " + cause); } } } /** * Create the Properties object from a map - masking out system properties * that are not intended for public access. */ private static Properties createProperties(Map<String, String> initialProps) { Properties properties = new Properties(initialProps.size()); for (var entry : initialProps.entrySet()) { String prop = entry.getKey(); switch (prop) { // Do not add private system properties to the Properties case "sun.nio.MaxDirectMemorySize": case "sun.nio.PageAlignDirectMemory": // used by java.lang.Integer.IntegerCache case "java.lang.Integer.IntegerCache.high": // used by sun.launcher.LauncherHelper case "sun.java.launcher.diag": // used by jdk.internal.loader.ClassLoaders case "jdk.boot.class.path.append": break; default: properties.put(prop, entry.getValue()); } } return properties; } /** * Initialize the system class. Called after thread initialization. */ private static void initPhase1() { // VM might invoke JNU_NewStringPlatform() to set those encoding // sensitive properties (user.home, user.name, boot.class.path, etc.) // during "props" initialization. // The charset is initialized in System.c and does not depend on the Properties. Map<String, String> tempProps = SystemProps.initProperties(); VersionProps.init(tempProps); // There are certain system configurations that may be controlled by // VM options such as the maximum amount of direct memory and // Integer cache size used to support the object identity semantics // of autoboxing. Typically, the library will obtain these values // from the properties set by the VM. If the properties are for // internal implementation use only, these properties should be // masked from the system properties. // // Save a private copy of the system properties object that // can only be accessed by the internal implementation. VM.saveProperties(tempProps); props = createProperties(tempProps); StaticProperty.javaHome(); // Load StaticProperty to cache the property values lineSeparator = props.getProperty("line.separator"); FileInputStream fdIn = new FileInputStream(FileDescriptor.in); FileOutputStream fdOut = new FileOutputStream(FileDescriptor.out); FileOutputStream fdErr = new FileOutputStream(FileDescriptor.err); setIn0(new BufferedInputStream(fdIn)); setOut0(newPrintStream(fdOut, props.getProperty("sun.stdout.encoding"))); setErr0(newPrintStream(fdErr, props.getProperty("sun.stderr.encoding"))); // Setup Java signal handlers for HUP, TERM, and INT (where available). Terminator.setup(); // Initialize any miscellaneous operating system settings that need to be // set for the class libraries. Currently this is no-op everywhere except // for Windows where the process-wide error mode is set before the java.io // classes are used. VM.initializeOSEnvironment(); // The main thread is not added to its thread group in the same // way as other threads; we must do it ourselves here. Thread current = Thread.currentThread(); current.getThreadGroup().add(current); // register shared secrets setJavaLangAccess(); // Subsystems that are invoked during initialization can invoke // VM.isBooted() in order to avoid doing things that should // wait until the VM is fully initialized. The initialization level // is incremented from 0 to 1 here to indicate the first phase of // initialization has completed. // IMPORTANT: Ensure that this remains the last initialization action! VM.initLevel(1); } // @see #initPhase2() static ModuleLayer bootLayer; /* * Invoked by VM. Phase 2 module system initialization. * Only classes in java.base can be loaded in this phase. * * @param printToStderr print exceptions to stderr rather than stdout * @param printStackTrace print stack trace when exception occurs * * @return JNI_OK for success, JNI_ERR for failure */ private static int initPhase2(boolean printToStderr, boolean printStackTrace) { try { bootLayer = ModuleBootstrap.boot(); } catch (Exception | Error e) { logInitException(printToStderr, printStackTrace, "Error occurred during initialization of boot layer", e); return -1; // JNI_ERR } // module system initialized VM.initLevel(2); return 0; // JNI_OK } /* * Invoked by VM. Phase 3 is the final system initialization: * 1. set security manager * 2. set system class loader * 3. set TCCL * * This method must be called after the module system initialization. * The security manager and system class loader may be a custom class from * the application classpath or modulepath. */ private static void initPhase3() { String smProp = System.getProperty("java.security.manager"); if (smProp != null) { switch (smProp) { case "disallow": allowSecurityManager = NEVER; break; case "allow": allowSecurityManager = MAYBE; break; case "": case "default": setSecurityManager(new SecurityManager()); allowSecurityManager = MAYBE; break; default: try { ClassLoader cl = ClassLoader.getBuiltinAppClassLoader(); Class<?> c = Class.forName(smProp, false, cl); Constructor<?> ctor = c.getConstructor(); // Must be a public subclass of SecurityManager with // a public no-arg constructor if (!SecurityManager.class.isAssignableFrom(c) || !Modifier.isPublic(c.getModifiers()) || !Modifier.isPublic(ctor.getModifiers())) { throw new Error("Could not create SecurityManager: " + ctor.toString()); } // custom security manager may be in non-exported package ctor.setAccessible(true); SecurityManager sm = (SecurityManager) ctor.newInstance(); setSecurityManager(sm); } catch (Exception e) { throw new InternalError("Could not create SecurityManager", e); } allowSecurityManager = MAYBE; } } else { allowSecurityManager = MAYBE; } // initializing the system class loader VM.initLevel(3); // system class loader initialized ClassLoader scl = ClassLoader.initSystemClassLoader(); // set TCCL Thread.currentThread().setContextClassLoader(scl); // system is fully initialized VM.initLevel(4); } private static void setJavaLangAccess() { // Allow privileged classes outside of java.lang SharedSecrets.setJavaLangAccess(new JavaLangAccess() { public List<Method> getDeclaredPublicMethods(Class<?> klass, String name, Class<?>... parameterTypes) { return klass.getDeclaredPublicMethods(name, parameterTypes); } public jdk.internal.reflect.ConstantPool getConstantPool(Class<?> klass) { return klass.getConstantPool(); } public boolean casAnnotationType(Class<?> klass, AnnotationType oldType, AnnotationType newType) { return klass.casAnnotationType(oldType, newType); } public AnnotationType getAnnotationType(Class<?> klass) { return klass.getAnnotationType(); } public Map<Class<? extends Annotation>, Annotation> getDeclaredAnnotationMap(Class<?> klass) { return klass.getDeclaredAnnotationMap(); } public byte[] getRawClassAnnotations(Class<?> klass) { return klass.getRawAnnotations(); } public byte[] getRawClassTypeAnnotations(Class<?> klass) { return klass.getRawTypeAnnotations(); } public byte[] getRawExecutableTypeAnnotations(Executable executable) { return Class.getExecutableTypeAnnotationBytes(executable); } public <E extends Enum<E>> E[] getEnumConstantsShared(Class<E> klass) { return klass.getEnumConstantsShared(); } public void blockedOn(Interruptible b) { Thread.blockedOn(b); } public void registerShutdownHook(int slot, boolean registerShutdownInProgress, Runnable hook) { Shutdown.add(slot, registerShutdownInProgress, hook); } public Thread newThreadWithAcc(Runnable target, AccessControlContext acc) { return new Thread(target, acc); } @SuppressWarnings("deprecation") public void invokeFinalize(Object o) throws Throwable { o.finalize(); } public ConcurrentHashMap<?, ?> createOrGetClassLoaderValueMap(ClassLoader cl) { return cl.createOrGetClassLoaderValueMap(); } public Class<?> defineClass(ClassLoader loader, String name, byte[] b, ProtectionDomain pd, String source) { return ClassLoader.defineClass1(loader, name, b, 0, b.length, pd, source); } public Class<?> findBootstrapClassOrNull(ClassLoader cl, String name) { return cl.findBootstrapClassOrNull(name); } public Package definePackage(ClassLoader cl, String name, Module module) { return cl.definePackage(name, module); } public String fastUUID(long lsb, long msb) { return Long.fastUUID(lsb, msb); } public void addNonExportedPackages(ModuleLayer layer) { SecurityManager.addNonExportedPackages(layer); } public void invalidatePackageAccessCache() { SecurityManager.invalidatePackageAccessCache(); } public Module defineModule(ClassLoader loader, ModuleDescriptor descriptor, URI uri) { return new Module(null, loader, descriptor, uri); } public Module defineUnnamedModule(ClassLoader loader) { return new Module(loader); } public void addReads(Module m1, Module m2) { m1.implAddReads(m2); } public void addReadsAllUnnamed(Module m) { m.implAddReadsAllUnnamed(); } public void addExports(Module m, String pn, Module other) { m.implAddExports(pn, other); } public void addExportsToAllUnnamed(Module m, String pn) { m.implAddExportsToAllUnnamed(pn); } public void addOpens(Module m, String pn, Module other) { m.implAddOpens(pn, other); } public void addOpensToAllUnnamed(Module m, String pn) { m.implAddOpensToAllUnnamed(pn); } public void addOpensToAllUnnamed(Module m, Iterator<String> packages) { m.implAddOpensToAllUnnamed(packages); } public void addUses(Module m, Class<?> service) { m.implAddUses(service); } public boolean isReflectivelyExported(Module m, String pn, Module other) { return m.isReflectivelyExported(pn, other); } public boolean isReflectivelyOpened(Module m, String pn, Module other) { return m.isReflectivelyOpened(pn, other); } public ServicesCatalog getServicesCatalog(ModuleLayer layer) { return layer.getServicesCatalog(); } public Stream<ModuleLayer> layers(ModuleLayer layer) { return layer.layers(); } public Stream<ModuleLayer> layers(ClassLoader loader) { return ModuleLayer.layers(loader); } public String newStringNoRepl(byte[] bytes, Charset cs) throws CharacterCodingException { return StringCoding.newStringNoRepl(bytes, cs); } public byte[] getBytesNoRepl(String s, Charset cs) throws CharacterCodingException { return StringCoding.getBytesNoRepl(s, cs); } public String newStringUTF8NoRepl(byte[] bytes, int off, int len) { return StringCoding.newStringUTF8NoRepl(bytes, off, len); } public byte[] getBytesUTF8NoRepl(String s) { return StringCoding.getBytesUTF8NoRepl(s); } public void setCause(Throwable t, Throwable cause) { t.setCause(cause); } }); } }