1 /*
   2  * Copyright (c) 2005, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.lang.management;
  27 
  28 import javax.management.openmbean.CompositeData;
  29 import java.util.concurrent.locks.*;
  30 import sun.management.LockInfoCompositeData;
  31 
  32 /**
  33  * Information about a <em>lock</em>.  A lock can be a built-in object monitor,
  34  * an <em>ownable synchronizer</em>, or the {@link Condition Condition}
  35  * object associated with synchronizers.
  36  * <p>
  37  * <a id="OwnableSynchronizer">An ownable synchronizer</a> is
  38  * a synchronizer that may be exclusively owned by a thread and uses
  39  * {@link AbstractOwnableSynchronizer AbstractOwnableSynchronizer}
  40  * (or its subclass) to implement its synchronization property.
  41  * {@link ReentrantLock ReentrantLock} and the write-lock (but not
  42  * the read-lock) of {@link ReentrantReadWriteLock ReentrantReadWriteLock} are
  43  * two examples of ownable synchronizers provided by the platform.
  44  *
  45  * <h3><a id="MappedType">MXBean Mapping</a></h3>
  46  * {@code LockInfo} is mapped to a {@link CompositeData CompositeData}
  47  * as specified in the {@link #from from} method.
  48  *
  49  * @see java.util.concurrent.locks.AbstractOwnableSynchronizer
  50  * @see java.util.concurrent.locks.Condition
  51  *
  52  * @author  Mandy Chung
  53  * @since   1.6
  54  */
  55 
  56 public class LockInfo {
  57 
  58     private String className;
  59     private int    identityHashCode;
  60 
  61     /**
  62      * Constructs a {@code LockInfo} object.
  63      *
  64      * @param className the fully qualified name of the class of the lock object.
  65      * @param identityHashCode the {@link System#identityHashCode
  66      *                         identity hash code} of the lock object.
  67      */
  68     public LockInfo(String className, int identityHashCode) {
  69         if (className == null) {
  70             throw new NullPointerException("Parameter className cannot be null");
  71         }
  72         this.className = className;
  73         this.identityHashCode = identityHashCode;
  74     }
  75 
  76     /**
  77      * package-private constructors
  78      */
  79     LockInfo(Object lock) {
  80         this.className = lock.getClass().getName();
  81         this.identityHashCode = System.identityHashCode(lock);
  82     }
  83 
  84     /**
  85      * Returns the fully qualified name of the class of the lock object.
  86      *
  87      * @return the fully qualified name of the class of the lock object.
  88      */
  89     public String getClassName() {
  90         return className;
  91     }
  92 
  93     /**
  94      * Returns the identity hash code of the lock object
  95      * returned from the {@link System#identityHashCode} method.
  96      *
  97      * @return the identity hash code of the lock object.
  98      */
  99     public int getIdentityHashCode() {
 100         return identityHashCode;
 101     }
 102 
 103     /**
 104      * Returns a {@code LockInfo} object represented by the
 105      * given {@code CompositeData}.
 106      * The given {@code CompositeData} must contain the following attributes:
 107      * <table class="striped" style="margin-left:2em;">
 108      * <caption style="display:none">The attributes and the types the given CompositeData contains</caption>
 109      * <thead style="text-align:left">
 110      * <tr>
 111      *   <th scope="col">Attribute Name</th>
 112      *   <th scope="col">Type</th>
 113      * </tr>
 114      * </thead>
 115      * <tbody style="text-align:left">
 116      * <tr>
 117      *   <th scope="row">className</th>
 118      *   <td>{@code java.lang.String}</td>
 119      * </tr>
 120      * <tr>
 121      *   <th scope="row">identityHashCode</th>
 122      *   <td>{@code java.lang.Integer}</td>
 123      * </tr>
 124      * </tbody>
 125      * </table>
 126      *
 127      * @param cd {@code CompositeData} representing a {@code LockInfo}
 128      *
 129      * @throws IllegalArgumentException if {@code cd} does not
 130      *   represent a {@code LockInfo} with the attributes described
 131      *   above.
 132      * @return a {@code LockInfo} object represented
 133      *         by {@code cd} if {@code cd} is not {@code null};
 134      *         {@code null} otherwise.
 135      *
 136      * @since 1.8
 137      */
 138     public static LockInfo from(CompositeData cd) {
 139         if (cd == null) {
 140             return null;
 141         }
 142 
 143         if (cd instanceof LockInfoCompositeData) {
 144             return ((LockInfoCompositeData) cd).getLockInfo();
 145         } else {
 146             return LockInfoCompositeData.toLockInfo(cd);
 147         }
 148     }
 149 
 150     /**
 151      * Returns a string representation of a lock.  The returned
 152      * string representation consists of the name of the class of the
 153      * lock object, the at-sign character `@', and the unsigned
 154      * hexadecimal representation of the <em>identity</em> hash code
 155      * of the object.  This method returns a string equals to the value of:
 156      * <blockquote>
 157      * <pre>
 158      * lock.getClass().getName() + '@' + Integer.toHexString(System.identityHashCode(lock))
 159      * </pre></blockquote>
 160      * where {@code lock} is the lock object.
 161      *
 162      * @return the string representation of a lock.
 163      */
 164     public String toString() {
 165         return className + '@' + Integer.toHexString(identityHashCode);
 166     }
 167 }