Source for java.rmi.server.ObjID

   1: /* ObjID.java -- Unique object id with respect to the given host.
   2:    Copyright (c) 1996, 1997, 1998, 1999, 2004, 2006
   3:    Free Software Foundation, Inc.
   4: 
   5: This file is part of GNU Classpath.
   6: 
   7: GNU Classpath is free software; you can redistribute it and/or modify
   8: it under the terms of the GNU General Public License as published by
   9: the Free Software Foundation; either version 2, or (at your option)
  10: any later version.
  11: 
  12: GNU Classpath is distributed in the hope that it will be useful, but
  13: WITHOUT ANY WARRANTY; without even the implied warranty of
  14: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15: General Public License for more details.
  16: 
  17: You should have received a copy of the GNU General Public License
  18: along with GNU Classpath; see the file COPYING.  If not, write to the
  19: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  20: 02110-1301 USA.
  21: 
  22: Linking this library statically or dynamically with other modules is
  23: making a combined work based on this library.  Thus, the terms and
  24: conditions of the GNU General Public License cover the whole
  25: combination.
  26: 
  27: As a special exception, the copyright holders of this library give you
  28: permission to link this library with independent modules to produce an
  29: executable, regardless of the license terms of these independent
  30: modules, and to copy and distribute the resulting executable under
  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 java.rmi.server;
  41: 
  42: import java.io.DataInput;
  43: import java.io.DataOutput;
  44: import java.io.IOException;
  45: import java.io.ObjectInput;
  46: import java.io.ObjectOutput;
  47: import java.io.Serializable;
  48: 
  49: /**
  50:  * Represents the object identifier, unique for the host that generated it.
  51:  * The ObjID contains inside the integer object identifier that, if needed,
  52:  * may indicated that this is a reference to one of the well known objects
  53:  * on that host (registry, activator or dgc) and the {@link UID} that
  54:  * ensures uniqueness.
  55:  */
  56: public final class ObjID
  57:     implements Serializable
  58: {
  59: 
  60:   /**
  61:    * Use serial version uid for interoperability.
  62:    */
  63:   static final long serialVersionUID = - 6386392263968365220L;
  64: 
  65:   /**
  66:    * The object counter, which value is assigned when creating the ordinary
  67:    * objects without the known object id. The counter is incremented each time
  68:    * the new ObjID is constructed.
  69:    */
  70:   private static long next = 0x8000000000000000L;
  71: 
  72:   /**
  73:    * The object to put the lock on when incrementing {@link #next}
  74:    */
  75:   private static final Object lock = ObjID.class;
  76: 
  77:   /**
  78:    * Defines the ID of the naming service.
  79:    */
  80:   public static final int REGISTRY_ID = 0;
  81: 
  82:   /**
  83:    * Defines the ID of the activator.
  84:    */
  85:   public static final int ACTIVATOR_ID = 1;
  86: 
  87:   /**
  88:    * Defines the ID of the distributed garbage collector.
  89:    */
  90:   public static final int DGC_ID = 2;
  91: 
  92:   /**
  93:    * The object Id (either well-known value or the value of the incrementing
  94:    * object counter.
  95:    */
  96:   long objNum;
  97: 
  98:   /**
  99:    * The object unique identifier, generated individually for each object.
 100:    */
 101:   UID space;
 102: 
 103:   /**
 104:    * Create the new object id, unique for this host.
 105:    */
 106:   public ObjID()
 107:   {
 108:     synchronized (lock)
 109:       {
 110:         objNum = next++;
 111:       }
 112:     space = new UID();
 113:   }
 114: 
 115:   /**
 116:    * Create the new object id defining the well known remotely accessible
 117:    * object, present in this host. The well - known objects are:
 118:    * <ul>
 119:    * <li>{@link #REGISTRY_ID} - RMI naming service.</li>
 120:    * <li>{@link #ACTIVATOR_ID} - activator</li>
 121:    * <li>{@link #DGC_ID} - distributed garbage collector (grants lease
 122:    * durations to keep the object before it is garbage collected.</li>
 123:    * </ul>
 124:    *
 125:    * @param id the well known object id, one of the above.
 126:    */
 127:   public ObjID(int id)
 128:   {
 129:     objNum = (long) id;
 130:     space = new UID((short) 0);
 131:   }
 132: 
 133:   /**
 134:    * Write object id as long, then the object {@link UID}.
 135:    */
 136:   public void write(ObjectOutput out) throws IOException
 137:   {
 138:     DataOutput dout = (DataOutput) out;
 139:     dout.writeLong(objNum);
 140:     space.write(dout);
 141:   }
 142: 
 143:   /**
 144:    * Read object id (as long), then the object {@link UID}.
 145:    */
 146:   public static ObjID read(ObjectInput in) throws IOException
 147:   {
 148:     DataInput din = (DataInput) in;
 149:     ObjID id = new ObjID();
 150:     id.objNum = din.readLong();
 151:     id.space = UID.read(din);
 152:     return (id);
 153:   }
 154: 
 155:   /**
 156:    * Get the hashcode.
 157:    */
 158:   public int hashCode()
 159:   {
 160:     return space == null ? (int) objNum : space.hashCode() ^ (int) objNum;
 161:   }
 162: 
 163:   /**
 164:    * Compare for equality.
 165:    */
 166:   public boolean equals(Object obj)
 167:   {
 168:     if (obj instanceof ObjID)
 169:       {
 170:         ObjID that = (ObjID) obj;
 171:         return that.objNum == objNum && eq(that.space, space);
 172:       }
 173:     else
 174:       return false;
 175:   }
 176: 
 177:   /**
 178:    * Compare by .equals if both a and b are not null, compare directly if at
 179:    * least one of them is null.
 180:    */
 181:   static final boolean eq(Object a, Object b)
 182:   {
 183:     if (a == null || b == null)
 184:       return a == b;
 185:     else
 186:       return a.equals(b);
 187:   }
 188: 
 189:   /**
 190:    * Get the string representation.
 191:    */
 192:   public String toString()
 193:   {
 194:     return (objNum + ":" + space);
 195:   }
 196: 
 197: }