Java tutorial
/* * Copyright 2002-2008 the original author or authors. * * Licensed under the Apache License, Version 2.0 (the "License"); you may not * use this file except in compliance with the License. You may obtain a copy of * the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations under * the License. */ package com.liferay.cli.support.util; import java.lang.reflect.Constructor; import java.lang.reflect.Field; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.lang.reflect.Modifier; import java.sql.SQLException; import java.util.ArrayList; import java.util.Arrays; import java.util.List; import org.apache.commons.lang3.Validate; /** * Simple utility class for working with the reflection API and handling * reflection exceptions. * <p> * Only intended for internal use. * * @author Juergen Hoeller * @author Rob Harrop * @author Rod Johnson * @author Costin Leau * @author Sam Brannen * @since 1.2.2 */ @Deprecated public abstract class ReflectionUtils { /** * Callback interface invoked on each field in the hierarchy. */ public static interface FieldCallback { /** * Perform an operation using the given field. * * @param field the field to operate on */ void doWith(Field field) throws IllegalArgumentException, IllegalAccessException; } /** * Callback optionally used to filter fields to be operated on by a field * callback. */ public static interface FieldFilter { /** * Determine whether the given field matches. * * @param field the field to check */ boolean matches(Field field); } /** * Action to take on each method. */ public static interface MethodCallback { /** * Perform an operation using the given method. * * @param method the method to operate on */ void doWith(Method method) throws IllegalArgumentException, IllegalAccessException; } /** * Callback optionally used to method fields to be operated on by a method * callback. */ public static interface MethodFilter { /** * Determine whether the given method matches. * * @param method the method to check */ boolean matches(Method method); } /** * Pre-built FieldFilter that matches all non-static, non-final fields. */ public static FieldFilter COPYABLE_FIELDS = new FieldFilter() { public boolean matches(final Field field) { return !(Modifier.isStatic(field.getModifiers()) || Modifier.isFinal(field.getModifiers())); } }; /** * Determine whether the given method explicitly declares the given * exception or one of its superclasses, which means that an exception of * that type can be propagated as-is within a reflective invocation. * * @param method the declaring method * @param exceptionType the exception to throw * @return <code>true</code> if the exception can be thrown as-is; * <code>false</code> if it needs to be wrapped */ public static boolean declaresException(final Method method, final Class<?> exceptionType) { Validate.notNull(method, "Method must not be null"); final Class<?>[] declaredExceptions = method.getExceptionTypes(); for (final Class<?> declaredException : declaredExceptions) { if (declaredException.isAssignableFrom(exceptionType)) { return true; } } return false; } /** * Invoke the given callback on all fields in the target class, going up the * class hierarchy to get all declared fields. * * @param targetClass the target class to analyze * @param fc the callback to invoke for each field */ public static void doWithFields(final Class<?> targetClass, final FieldCallback fc) throws IllegalArgumentException { doWithFields(targetClass, fc, null); } /** * Invoke the given callback on all fields in the target class, going up the * class hierarchy to get all declared fields. * * @param targetClass the target class to analyze * @param fc the callback to invoke for each field * @param ff the filter that determines the fields to apply the callback to */ public static void doWithFields(Class<?> targetClass, final FieldCallback fc, final FieldFilter ff) throws IllegalArgumentException { // Keep backing up the inheritance hierarchy. do { // Copy each field declared on this class unless it's static or // file. final Field[] fields = targetClass.getDeclaredFields(); for (final Field field : fields) { // Skip static and final fields. if (ff != null && !ff.matches(field)) { continue; } try { fc.doWith(field); } catch (final IllegalAccessException ex) { throw new IllegalStateException( "Shouldn't be illegal to access field '" + field.getName() + "': " + ex); } } targetClass = targetClass.getSuperclass(); } while (targetClass != null && targetClass != Object.class); } /** * Perform the given callback operation on all matching methods of the given * class and superclasses. * <p> * The same named method occurring on subclass and superclass will appear * twice, unless excluded by a {@link MethodFilter}. * * @param targetClass class to start looking at * @param mc the callback to invoke for each method * @see #doWithMethods(Class, MethodCallback, MethodFilter) */ public static void doWithMethods(final Class<?> targetClass, final MethodCallback mc) throws IllegalArgumentException { doWithMethods(targetClass, mc, null); } /** * Perform the given callback operation on all matching methods of the given * class and superclasses. * <p> * The same named method occurring on subclass and superclass will appear * twice, unless excluded by the specified {@link MethodFilter}. * * @param targetClass class to start looking at * @param mc the callback to invoke for each method * @param mf the filter that determines the methods to apply the callback to */ public static void doWithMethods(Class<?> targetClass, final MethodCallback mc, final MethodFilter mf) throws IllegalArgumentException { // Keep backing up the inheritance hierarchy. do { final Method[] methods = targetClass.getDeclaredMethods(); for (final Method method : methods) { if (mf != null && !mf.matches(method)) { continue; } try { mc.doWith(method); } catch (final IllegalAccessException ex) { throw new IllegalStateException( "Shouldn't be illegal to access method '" + method.getName() + "': " + ex); } } targetClass = targetClass.getSuperclass(); } while (targetClass != null); } /** * Attempt to find a {@link Field field} on the supplied {@link Class} with * the supplied <code>name</code>. Searches all superclasses up to * {@link Object}. * * @param clazz the class to introspect * @param name the name of the field * @return the corresponding Field object, or <code>null</code> if not found */ public static Field findField(final Class<?> clazz, final String name) { return findField(clazz, name, null); } /** * Attempt to find a {@link Field field} on the supplied {@link Class} with * the supplied <code>name</code> and/or {@link Class type}. Searches all * superclasses up to {@link Object}. * * @param clazz the class to introspect * @param name the name of the field (may be <code>null</code> if type is * specified) * @param type the type of the field (may be <code>null</code> if name is * specified) * @return the corresponding Field object, or <code>null</code> if not found */ public static Field findField(final Class<?> clazz, final String name, final Class<?> type) { Validate.notNull(clazz, "Class must not be null"); Validate.isTrue(name != null || type != null, "Either name or type of the field must be specified"); Class<?> searchType = clazz; while (!Object.class.equals(searchType) && searchType != null) { final Field[] fields = searchType.getDeclaredFields(); for (final Field field : fields) { if ((name == null || name.equals(field.getName())) && (type == null || type.equals(field.getType()))) { return field; } } searchType = searchType.getSuperclass(); } return null; } /** * Attempt to find a {@link Method} on the supplied class with the supplied * name and no parameters. Searches all superclasses up to * <code>Object</code>. * <p> * Returns <code>null</code> if no {@link Method} can be found. * * @param clazz the class to introspect * @param name the name of the method * @return the Method object, or <code>null</code> if none found */ public static Method findMethod(final Class<?> clazz, final String name) { return findMethod(clazz, name, new Class[0]); } /** * Attempt to find a {@link Method} on the supplied class with the supplied * name and parameter types. Searches all superclasses up to * <code>Object</code>. * <p> * Returns <code>null</code> if no {@link Method} can be found. * * @param clazz the class to introspect * @param name the name of the method * @param parameterTypes the parameter types of the method (may be * <code>null</code> to indicate any signature) * @return the Method object, or <code>null</code> if none found */ public static Method findMethod(final Class<?> clazz, final String name, final Class<?>[] parameterTypes) { Validate.notNull(clazz, "Class must not be null"); Validate.notNull(name, "Method name must not be null"); Class<?> searchType = clazz; while (!Object.class.equals(searchType) && searchType != null) { final Method[] methods = searchType.isInterface() ? searchType.getMethods() : searchType.getDeclaredMethods(); for (final Method method : methods) { if (name.equals(method.getName()) && (parameterTypes == null || Arrays.equals(parameterTypes, method.getParameterTypes()))) { return method; } } searchType = searchType.getSuperclass(); } return null; } /** * Get all declared methods on the leaf class and all superclasses. Leaf * class methods are included first. */ public static Method[] getAllDeclaredMethods(final Class<?> leafClass) throws IllegalArgumentException { final List<Method> methods = new ArrayList<Method>(32); doWithMethods(leafClass, new MethodCallback() { public void doWith(final Method method) { methods.add(method); } }); return methods.toArray(new Method[methods.size()]); } /** * Get the field represented by the supplied {@link Field field object} on * the specified {@link Object target object}. In accordance with * {@link Field#get(Object)} semantics, the returned value is automatically * wrapped if the underlying field has a primitive type. * <p> * Thrown exceptions are handled via a call to * {@link #handleReflectionException(Exception)}. * * @param field the field to get * @param target the target object from which to get the field * @return the field's current value */ public static Object getField(final Field field, final Object target) { try { return field.get(target); } catch (final IllegalAccessException ex) { handleReflectionException(ex); throw new IllegalStateException( "Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage()); } } /** * Handle the given invocation target exception. Should only be called if no * checked exception is expected to be thrown by the target method. * <p> * Throws the underlying RuntimeException or Error in case of such a root * cause. Throws an IllegalStateException else. * * @param ex the invocation target exception to handle */ public static void handleInvocationTargetException(final InvocationTargetException ex) { rethrowRuntimeException(ex.getTargetException()); } /** * Handle the given reflection exception. Should only be called if no * checked exception is expected to be thrown by the target method. * <p> * Throws the underlying RuntimeException or Error in case of an * InvocationTargetException with such a root cause. Throws an * IllegalStateException with an appropriate message else. * * @param ex the reflection exception to handle */ public static void handleReflectionException(final Exception ex) { if (ex instanceof NoSuchMethodException) { throw new IllegalStateException("Method not found: " + ex.getMessage()); } if (ex instanceof IllegalAccessException) { throw new IllegalStateException("Could not access method: " + ex.getMessage()); } if (ex instanceof InvocationTargetException) { handleInvocationTargetException((InvocationTargetException) ex); } if (ex instanceof RuntimeException) { throw (RuntimeException) ex; } handleUnexpectedException(ex); } /** * Throws an IllegalStateException with the given exception as root cause. * * @param ex the unexpected exception */ private static void handleUnexpectedException(final Throwable ex) { throw new IllegalStateException("Unexpected exception thrown", ex); } /** * Invoke the specified JDBC API {@link Method} against the supplied target * object with no arguments. * * @param method the method to invoke * @param target the target object to invoke the method on * @return the invocation result, if any * @throws SQLException the JDBC API SQLException to rethrow (if any) * @see #invokeJdbcMethod(java.lang.reflect.Method, Object, Object[]) */ public static Object invokeJdbcMethod(final Method method, final Object target) throws SQLException { return invokeJdbcMethod(method, target, null); } /** * Invoke the specified JDBC API {@link Method} against the supplied target * object with the supplied arguments. * * @param method the method to invoke * @param target the target object to invoke the method on * @param args the invocation arguments (may be <code>null</code>) * @return the invocation result, if any * @throws SQLException the JDBC API SQLException to rethrow (if any) * @see #invokeMethod(java.lang.reflect.Method, Object, Object[]) */ public static Object invokeJdbcMethod(final Method method, final Object target, final Object[] args) throws SQLException { try { return method.invoke(target, args); } catch (final IllegalAccessException ex) { handleReflectionException(ex); } catch (final InvocationTargetException ex) { if (ex.getTargetException() instanceof SQLException) { throw (SQLException) ex.getTargetException(); } handleInvocationTargetException(ex); } throw new IllegalStateException("Should never get here"); } /** * Invoke the specified {@link Method} against the supplied target object * with no arguments. The target object can be <code>null</code> when * invoking a static {@link Method}. * <p> * Thrown exceptions are handled via a call to * {@link #handleReflectionException}. * * @param method the method to invoke * @param target the target object to invoke the method on * @return the invocation result, if any * @see #invokeMethod(java.lang.reflect.Method, Object, Object[]) */ public static Object invokeMethod(final Method method, final Object target) { return invokeMethod(method, target, null); } /** * Invoke the specified {@link Method} against the supplied target object * with the supplied arguments. The target object can be <code>null</code> * when invoking a static {@link Method}. * <p> * Thrown exceptions are handled via a call to * {@link #handleReflectionException}. * * @param method the method to invoke * @param target the target object to invoke the method on * @param args the invocation arguments (may be <code>null</code>) * @return the invocation result, if any */ public static Object invokeMethod(final Method method, final Object target, final Object[] args) { try { return method.invoke(target, args); } catch (final Exception ex) { handleReflectionException(ex); } throw new IllegalStateException("Should never get here"); } /** * Determine whether the given method is an "equals" method. * * @see java.lang.Object#equals */ public static boolean isEqualsMethod(final Method method) { if (method == null || !method.getName().equals("equals")) { return false; } final Class<?>[] parameterTypes = method.getParameterTypes(); return parameterTypes.length == 1 && parameterTypes[0] == Object.class; } /** * Determine whether the given method is a "hashCode" method. * * @see java.lang.Object#hashCode */ public static boolean isHashCodeMethod(final Method method) { return method != null && method.getName().equals("hashCode") && method.getParameterTypes().length == 0; } /** * Determine whether the given field is a "public static final" constant. * * @param field the field to check */ public static boolean isPublicStaticFinal(final Field field) { final int modifiers = field.getModifiers(); return Modifier.isPublic(modifiers) && Modifier.isStatic(modifiers) && Modifier.isFinal(modifiers); } /** * Determine whether the given method is a "toString" method. * * @see java.lang.Object#toString() */ public static boolean isToStringMethod(final Method method) { return method != null && method.getName().equals("toString") && method.getParameterTypes().length == 0; } /** * Make the given constructor accessible, explicitly setting it accessible * if necessary. The <code>setAccessible(true)</code> method is only called * when actually necessary, to avoid unnecessary conflicts with a JVM * SecurityManager (if active). * * @param ctor the constructor to make accessible * @see java.lang.reflect.Constructor#setAccessible */ public static void makeAccessible(final Constructor<?> ctor) { if (!Modifier.isPublic(ctor.getModifiers()) || !Modifier.isPublic(ctor.getDeclaringClass().getModifiers())) { ctor.setAccessible(true); } } /** * Make the given field accessible, explicitly setting it accessible if * necessary. The <code>setAccessible(true)</code> method is only called * when actually necessary, to avoid unnecessary conflicts with a JVM * SecurityManager (if active). * * @param field the field to make accessible * @see java.lang.reflect.Field#setAccessible */ public static void makeAccessible(final Field field) { if (!Modifier.isPublic(field.getModifiers()) || !Modifier.isPublic(field.getDeclaringClass().getModifiers())) { field.setAccessible(true); } } /** * Make the given method accessible, explicitly setting it accessible if * necessary. The <code>setAccessible(true)</code> method is only called * when actually necessary, to avoid unnecessary conflicts with a JVM * SecurityManager (if active). * * @param method the method to make accessible * @see java.lang.reflect.Method#setAccessible */ public static void makeAccessible(final Method method) { if (!Modifier.isPublic(method.getModifiers()) || !Modifier.isPublic(method.getDeclaringClass().getModifiers())) { method.setAccessible(true); } } /** * Rethrow the given {@link Throwable exception}, which is presumably the * <em>target exception</em> of an {@link InvocationTargetException}. Should * only be called if no checked exception is expected to be thrown by the * target method. * <p> * Rethrows the underlying exception cast to an {@link Exception} or * {@link Error} if appropriate; otherwise, throws an * {@link IllegalStateException}. * * @param ex the exception to rethrow * @throws Exception the rethrown exception (in case of a checked exception) */ public static void rethrowException(final Throwable ex) throws Exception { if (ex instanceof Exception) { throw (Exception) ex; } if (ex instanceof Error) { throw (Error) ex; } handleUnexpectedException(ex); } /** * Rethrow the given {@link Throwable exception}, which is presumably the * <em>target exception</em> of an {@link InvocationTargetException}. Should * only be called if no checked exception is expected to be thrown by the * target method. * <p> * Rethrows the underlying exception cast to an {@link RuntimeException} or * {@link Error} if appropriate; otherwise, throws an * {@link IllegalStateException}. * * @param ex the exception to rethrow * @throws RuntimeException the rethrown exception */ public static void rethrowRuntimeException(final Throwable ex) { if (ex instanceof RuntimeException) { throw (RuntimeException) ex; } if (ex instanceof Error) { throw (Error) ex; } handleUnexpectedException(ex); } /** * Set the field represented by the supplied {@link Field field object} on * the specified {@link Object target object} to the specified * <code>value</code>. In accordance with {@link Field#set(Object, Object)} * semantics, the new value is automatically unwrapped if the underlying * field has a primitive type. * <p> * Thrown exceptions are handled via a call to * {@link #handleReflectionException(Exception)}. * * @param field the field to set * @param target the target object on which to set the field * @param value the value to set; may be <code>null</code> */ public static void setField(final Field field, final Object target, final Object value) { try { field.set(target, value); } catch (final IllegalAccessException ex) { handleReflectionException(ex); throw new IllegalStateException( "Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage()); } } /** * Given the source object and the destination, which must be the same class * or a subclass, copy all fields, including inherited fields. Designed to * work on objects with public no-arg constructors. * * @throws IllegalArgumentException if the arguments are incompatible */ public static void shallowCopyFieldState(final Object src, final Object dest) throws IllegalArgumentException { if (src == null) { throw new IllegalArgumentException("Source for field copy cannot be null"); } if (dest == null) { throw new IllegalArgumentException("Destination for field copy cannot be null"); } if (!src.getClass().isAssignableFrom(dest.getClass())) { throw new IllegalArgumentException("Destination class [" + dest.getClass().getName() + "] must be same or subclass as source class [" + src.getClass().getName() + "]"); } doWithFields(src.getClass(), new FieldCallback() { public void doWith(final Field field) throws IllegalArgumentException, IllegalAccessException { makeAccessible(field); final Object srcValue = field.get(src); field.set(dest, srcValue); } }, COPYABLE_FIELDS); } }