Source for gnu.classpath.jdwp.id.ObjectId

   1: /* ObjectId.java -- object IDs
   2:    Copyright (C) 2005, 2006 Free Software Foundation
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: terms of your choice, provided that you also meet, for each linked
  32: independent module, the terms and conditions of the license of that
  33: module.  An independent module is a module which is not derived from
  34: or based on this library.  If you modify this library, you may extend
  35: this exception to your version of the library, but you are not
  36: obligated to do so.  If you do not wish to do so, delete this
  37: exception statement from your version. */
  38: 
  39: 
  40: package gnu.classpath.jdwp.id;
  41: 
  42: import gnu.classpath.jdwp.JdwpConstants;
  43: import gnu.classpath.jdwp.exception.InvalidObjectException;
  44: 
  45: import java.io.DataOutputStream;
  46: import java.io.IOException;
  47: 
  48: /**
  49:  * This is a base class for all ObjectID-like entities in JDWP,
  50:  * inculding Objects, ClassObject, ClassLoader, Thread, ThreadGroup,
  51:  * etc.
  52:  *
  53:  * @author Keith Seitz  <keiths@redhat.com>
  54:  */
  55: public class ObjectId
  56:   extends JdwpId
  57: {
  58:   /**
  59:    * The object class that this id represents
  60:    */
  61:   public static final Class typeClass = Object.class;
  62: 
  63:   // Handle to disable garbage collection
  64:   private Object _handle;
  65: 
  66:   /**
  67:    * Constructs a new <code>ObjectId</code>
  68:    */
  69:   public ObjectId ()
  70:   {
  71:     super (JdwpConstants.Tag.OBJECT);
  72:   }
  73: 
  74:   /**
  75:    * Constructs a new <code>ObjectId</code> of the
  76:    * given type.
  77:    *
  78:    * @param  tag  the tag of this type of object ID
  79:    */
  80:   public ObjectId (byte tag)
  81:   {
  82:     super (tag);
  83:   }
  84: 
  85:   /**
  86:    * Returns the object referred to by this ID
  87:    *
  88:    * @returns the object
  89:    * @throws InvalidObjectException if the object was garbage collected
  90:    *           or is invalid
  91:    */
  92:   public Object getObject ()
  93:     throws InvalidObjectException
  94:   {
  95:     Object obj = _reference.get ();
  96:     if (obj == null)
  97:       throw new InvalidObjectException (_id);
  98: 
  99:     return obj;
 100:   }
 101: 
 102:   /**
 103:    * Writes the id to the stream
 104:    *
 105:    * @param outStream  the stream to which to write
 106:    * @throws IOException  when an error occurs on the <code>OutputStream</code>
 107:    */
 108:   public void write (DataOutputStream outStream)
 109:     throws IOException
 110:   {
 111:     // All we need to do is write out our id as an 8-byte integer
 112:     outStream.writeLong (_id);
 113:   }
 114: 
 115:   /**
 116:    * Disable garbage collection on object
 117:    */
 118:   public void disableCollection ()
 119:     throws InvalidObjectException
 120:   {
 121:     _handle = getObject ();
 122:   }
 123: 
 124:   /**
 125:    * Enable garbage collection on object
 126:    */
 127:   public void enableCollection ()
 128:   {
 129:     _handle = null;
 130:   }
 131: }