OrderedSynchronizationHandler


1   package org.jboss.cache.interceptors;
2   
3   import org.apache.commons.logging.Log;
4   import org.apache.commons.logging.LogFactory;
5   
6   import javax.transaction.RollbackException  ;
7   import javax.transaction.Synchronization  ;
8   import javax.transaction.SystemException  ;
9   import javax.transaction.Transaction  ;
10  import java.util.HashMap  ;
11  import java.util.Iterator  ;
12  import java.util.LinkedList  ;
13  import java.util.Map  ;
14  
15  /**
16   * Maintains a list of Synchronization handlers. Reason is that we have to
17   * invoke certain handlers <em>before</em> others. See the description in
18   * SyncTxUnitTestCase.testConcurrentPuts(). For example, for synchronous
19   * replication, we have to execute the ReplicationInterceptor's
20   * afterCompletion() <em>before</em> the TransactionInterceptor's.
21   *
22   * @author Bela Ban
23   * @version $Id: OrderedSynchronizationHandler.java,v 1.4 2006/07/19 21:34:43 msurtani Exp $
24   */
25  public class OrderedSynchronizationHandler implements Synchronization   {
26     Transaction         tx=null;
27     LinkedList          handlers=new LinkedList  ();
28  
29     /** Map<Transaction,OrderedSynchronizationHandler> */
30     static Map   instances=new HashMap  ();
31  
32     static Log log=LogFactory.getLog(OrderedSynchronizationHandler.class);
33  
34  
35     private OrderedSynchronizationHandler(Transaction   tx) {
36        this.tx=tx;
37     }
38  
39     /**
40      * Creates a new instance of OrderedSynchronizationHandler, or fetches an existing instance. Key is the local
41      * transaction (tx). This instance registers with the TransactionManager automatically
42      * @param tx
43      */
44     public static OrderedSynchronizationHandler getInstance(Transaction   tx) throws SystemException  , RollbackException   {
45        OrderedSynchronizationHandler retval=(OrderedSynchronizationHandler)instances.get(tx);
46        if(retval != null) return retval;
47        retval=new OrderedSynchronizationHandler(tx);
48        tx.registerSynchronization(retval);
49        instances.put(tx, retval);
50        return retval;
51     }
52  
53  
54     public void registerAtHead(Synchronization   handler) {
55        register(handler, true);
56     }
57  
58     public void registerAtTail(Synchronization   handler) {
59        register(handler,  false);
60     }
61  
62     void register(Synchronization   handler, boolean head) {
63        if(handler != null && !handlers.contains(handler)) {
64           if(head)
65              handlers.addFirst(handler);
66           else
67              handlers.addLast(handler);
68        }
69     }
70  
71     public void beforeCompletion() {
72        for(Iterator   it=handlers.iterator(); it.hasNext();) {
73           Synchronization   sync=(Synchronization  )it.next();
74           sync.beforeCompletion();
75        }
76     }
77  
78     public void afterCompletion(int status) {
79        for(Iterator   it=handlers.iterator(); it.hasNext();) {
80           Synchronization   sync=(Synchronization  )it.next();
81           try {
82              sync.afterCompletion(status);
83           }
84           catch(Throwable   t) {
85              log.error("failed calling afterCompletion() on " + sync, t);
86           }
87        }
88  
89        // finally unregister us from the hashmap
90        instances.remove(tx);
91     }
92  
93     public String   toString() {
94        StringBuffer   sb=new StringBuffer  ();
95        sb.append("tx=" + tx + ", handlers=" + handlers);
96        return sb.toString();
97     }
98  }
99
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