StreamingSetStateEvent


1   package org.jgroups;
2   import java.io.InputStream  ;
3   /**
4    * 
5    * Represents an event returned by <code>channel.receive()</code>, as requested by
6    * <code>channel.getState()</code> previously.
7    * 
8    * <p>
9    * 
10   * Allows applications using a channel in a pull mode to receive a state from 
11   * another channel instance providing state. Channels have to be configured with
12   * <code>STREAMING_STATE_TRANSFER</code> protocol rather than the default 
13   * <code>STATE_TRANSFER</code> protocol in order to receive this event. 
14   * 
15   * <p>
16   * 
17   * The following code demonstrate how to pull events from a channel, processing 
18   * <code>StreamingSetStateEvent</code> and retrieving hypothetical state in the 
19   * form of LinkedList from event's <code>InputStream</code> reference.
20   * 
21   * <blockquote><pre>
22   *  Object obj=channel.receive(0);
23   *  if(obj instanceof StreamingSetStateEvent) {
24   *      StreamingSetStateEvent evt=(StreamingSetStateEvent)obj;
25   *      ObjectInputStream ois = null;       
26   *      try {           
27   *          ois = new ObjectInputStream(evt.getArg());
28   *          state = (LinkedList)ois.readObject();  
29   *      } catch (Exception e) {} 
30   *      finally
31   *      {
32   *          try {               
33   *              ois.close();
34   *          } catch (IOException e) {
35   *              System.err.println(e);
36   *          }
37   *      }                
38   *   }
39   * </pre></blockquote>
40   * 
41   * 
42   * @author Vladimir Blagojevic
43   * @see org.jgroups.JChannel#getState(Address, long)
44   * @see org.jgroups.StreamingMessageListener#setState(InputStream)
45   * @since 2.4
46   * 
47   */
48  public class StreamingSetStateEvent {
49  
50      InputStream   is;
51      String   state_id;
52      
53      public StreamingSetStateEvent(InputStream   is,String   state_id) {
54          super();
55          this.is=is;
56          this.state_id=state_id;
57      }
58      
59      /**
60       * Returns InputStream used for reading of a state.
61       * 
62       * @return the InputStream
63       */
64      public InputStream   getArg()
65      {
66          return is;
67      }
68      
69      
70      /**
71       * Returns id of the partial state if partial state was requested. 
72       * If full state transfer was requested this method will return null.
73       * 
74       * @see JChannel#getState(Address, long)
75       * @see JChannel#getState(Address, String, long)
76       * @return partial state id
77       */
78      public String   getStateId()
79      {
80          return state_id;
81      }   
82  
83  }
84
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