Java tutorial
/* * Copyright (c) 2005, 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.management; import javax.management.openmbean.CompositeData; import sun.management.MonitorInfoCompositeData; /** * Information about an object monitor lock. An object monitor is locked * when entering a synchronization block or method on that object. * * <h2>MXBean Mapping</h2> * {@code MonitorInfo} is mapped to a {@link CompositeData CompositeData} * with attributes as specified in * the {@link #from from} method. * * @author Mandy Chung * @since 1.6 */ public class MonitorInfo extends LockInfo { private int stackDepth; private StackTraceElement stackFrame; /** * Construct a {@code MonitorInfo} object. * * @param className the fully qualified name of the class of the lock object. * @param identityHashCode the {@link System#identityHashCode * identity hash code} of the lock object. * @param stackDepth the depth in the stack trace where the object monitor * was locked. * @param stackFrame the stack frame that locked the object monitor. * @throws IllegalArgumentException if * {@code stackDepth} ≥ 0 but {@code stackFrame} is {@code null}, * or {@code stackDepth} < 0 but {@code stackFrame} is not * {@code null}. */ public MonitorInfo(String className, int identityHashCode, int stackDepth, StackTraceElement stackFrame) { super(className, identityHashCode); if (stackDepth >= 0 && stackFrame == null) { throw new IllegalArgumentException("Parameter stackDepth is " + stackDepth + " but stackFrame is null"); } if (stackDepth < 0 && stackFrame != null) { throw new IllegalArgumentException( "Parameter stackDepth is " + stackDepth + " but stackFrame is not null"); } this.stackDepth = stackDepth; this.stackFrame = stackFrame; } /** * Returns the depth in the stack trace where the object monitor * was locked. The depth is the index to the {@code StackTraceElement} * array returned in the {@link ThreadInfo#getStackTrace} method. * * @return the depth in the stack trace where the object monitor * was locked, or a negative number if not available. */ public int getLockedStackDepth() { return stackDepth; } /** * Returns the stack frame that locked the object monitor. * * @return {@code StackTraceElement} that locked the object monitor, * or {@code null} if not available. */ public StackTraceElement getLockedStackFrame() { return stackFrame; } /** * Returns a {@code MonitorInfo} object represented by the * given {@code CompositeData}. * The given {@code CompositeData} must contain the following attributes * as well as the attributes specified in the * <a href="LockInfo.html#MappedType"> * mapped type</a> for the {@link LockInfo} class: * <table class="striped" style="margin-left:2em"> * <caption style="display:none">The attributes and their types the given CompositeData contains</caption> * <thead> * <tr> * <th scope="col">Attribute Name</th> * <th scope="col">Type</th> * </tr> * </thead> * <tbody style="text-align:left"> * <tr> * <th scope="row">lockedStackFrame</th> * <td><a href="ThreadInfo.html#stackTraceElement"> * {@code CompositeData} for {@code StackTraceElement}</a> as specified * in {@link ThreadInfo#from(CompositeData)} method. * </td> * </tr> * <tr> * <th scope="row">lockedStackDepth</th> * <td>{@code java.lang.Integer}</td> * </tr> * </tbody> * </table> * * @param cd {@code CompositeData} representing a {@code MonitorInfo} * * @throws IllegalArgumentException if {@code cd} does not * represent a {@code MonitorInfo} with the attributes described * above. * * @return a {@code MonitorInfo} object represented * by {@code cd} if {@code cd} is not {@code null}; * {@code null} otherwise. */ public static MonitorInfo from(CompositeData cd) { if (cd == null) { return null; } if (cd instanceof MonitorInfoCompositeData) { return ((MonitorInfoCompositeData) cd).getMonitorInfo(); } else { MonitorInfoCompositeData.validateCompositeData(cd); String className = MonitorInfoCompositeData.getClassName(cd); int identityHashCode = MonitorInfoCompositeData.getIdentityHashCode(cd); int stackDepth = MonitorInfoCompositeData.getLockedStackDepth(cd); StackTraceElement stackFrame = MonitorInfoCompositeData.getLockedStackFrame(cd); return new MonitorInfo(className, identityHashCode, stackDepth, stackFrame); } } }