001    /* MonitorInfo.java - Information on a monitor lock.
002       Copyright (C) 2006 Free Software Foundation
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    package java.lang.management;
039    
040    import javax.management.openmbean.CompositeData;
041    import javax.management.openmbean.CompositeType;
042    import javax.management.openmbean.SimpleType;
043    
044    /**
045     * Provides information on a monitor lock held by a thread.
046     * A monitor lock is obtained when a thread enters a synchronized
047     * block or method.
048     *
049     * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
050     * @since 1.6
051     */
052    public class MonitorInfo
053      extends LockInfo
054    {
055    
056      /**
057       * The stack depth at which the lock was obtained.
058       */
059      private int stackDepth;
060    
061      /**
062       * The stack frame at which the lock was obtained.
063       */
064      private StackTraceElement stackFrame;
065    
066      /**
067       * Constructs a new {@link MonitorInfo} using the specified
068       * lock class name and identity hash code, and the given
069       * stack depth and frame.
070       *
071       * @param className the class name of the lock object.
072       * @param identityHashCode the identity hash code of the lock object.
073       * @param stackDepth the depth of the stack at which the lock
074       *                   was obtained.
075       * @param stackFrame the frame of the stack at which the lock was
076       *                   obtained.
077       * @throws IllegalArgumentException if the stack depth and frame are
078       *                                  inconsistent i.e. the frame is
079       *                                  <code>null</code> but the depth is
080       *                                  &ge; 0, or the frame is not
081       *                                  <code>null</code> but the depth is
082       *                                  &lt; 0.
083       */
084      public MonitorInfo(String className, int identityHashCode, int stackDepth,
085                         StackTraceElement stackFrame)
086      {
087        super(className, identityHashCode);
088        if (stackFrame == null && stackDepth >= 0)
089          throw new IllegalArgumentException("The stack frame is null, but the " +
090                                             "stack depth is greater than or equal " +
091                                             "to zero.");
092        if (stackFrame != null && stackDepth < 0)
093          throw new IllegalArgumentException("The stack frame is not null, but the " +
094                                             "stack depth is less than zero.");
095        this.stackDepth = stackDepth;
096        this.stackFrame = stackFrame;
097      }
098    
099      /**
100       * <p>
101       * Returns a {@link MonitorInfo} instance using the values
102       * given in the supplied
103       * {@link javax.management.openmbean.CompositeData} object.
104       * The composite data instance should contain the following
105       * attributes with the specified types:
106       * </p>
107       * <table>
108       * <th><td>Name</td><td>Type</td></th>
109       * <tr><td>className</td><td>java.lang.String</td></tr>
110       * <tr><td>identityHashCode</td><td>java.lang.Integer</td></tr>
111       * <tr><td>lockedStackDepth</td><td>java.lang.Integer</td></tr>
112       * <tr><td>lockedStackFrame</td><td>javax.management.openmbean.CompositeData
113       * </td></tr>
114       * </table>
115       * <p>
116       * The stack trace is further described as:
117       * </p>
118       * <table>
119       * <th><td>Name</td><td>Type</td></th>
120       * <tr><td>className</td><td>java.lang.String</td></tr>
121       * <tr><td>methodName</td><td>java.lang.String</td></tr>
122       * <tr><td>fileName</td><td>java.lang.String</td></tr>
123       * <tr><td>lineNumber</td><td>java.lang.Integer</td></tr>
124       * <tr><td>nativeMethod</td><td>java.lang.Boolean</td></tr>
125       * </table>
126       *
127       * @param data the composite data structure to take values from.
128       * @return a new instance containing the values from the
129       *         composite data structure, or <code>null</code>
130       *         if the data structure was also <code>null</code>.
131       * @throws IllegalArgumentException if the composite data structure
132       *                                  does not match the structure
133       *                                  outlined above.
134       */
135      public static MonitorInfo from(CompositeData data)
136      {
137        if (data == null)
138          return null;
139        CompositeType type = data.getCompositeType();
140        ThreadInfo.checkAttribute(type, "ClassName", SimpleType.STRING);
141        ThreadInfo.checkAttribute(type, "IdentityHashCode", SimpleType.INTEGER);
142        ThreadInfo.checkAttribute(type, "LockedStackDepth", SimpleType.INTEGER);
143        ThreadInfo.checkAttribute(type, "LockedStackFrame",
144                                  ThreadInfo.getStackTraceType());
145        CompositeData frame = (CompositeData) data.get("LockedStackFrame");
146        return new MonitorInfo((String) data.get("ClassName"),
147                               (Integer) data.get("IdentityHashCode"),
148                               (Integer) data.get("LockedStackDepth"),
149                               new StackTraceElement((String) frame.get("ClassName"),
150                                                     (String) frame.get("MethodName"),
151                                                     (String) frame.get("FileName"),
152                                                     (Integer) frame.get("LineNumber")));
153      }
154    
155      /**
156       * Returns the depth of the stack at which the lock was obtained.
157       * This works as an index into the array returned by
158       * {@link ThreadInfo#getStackTrace()}.
159       *
160       * @return the depth of the stack at which the lock was obtained,
161       *         or a negative number if this information is unavailable.
162       */
163      public int getLockedStackDepth()
164      {
165        return stackDepth;
166      }
167    
168      /**
169       * Returns the stack frame at which the lock was obtained.
170       *
171       * @return the stack frame at which the lock was obtained,
172       *         or <code>null</code> if this informati0on is unavailable.
173       */
174      public StackTraceElement getLockedStackFrame()
175      {
176        return stackFrame;
177      }
178    
179    }