Added helper to get transactionally-bound List, Map and Set resources

- Generics allow the following, for instance:
   Map<NodeRef,List<QName>> filters = TransactionalResourceHelper.getMap(KEY_NODEREF_FILTER);


git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@13794 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/repo/transaction/AlfrescoTransactionSupport.java

@@ -202,8 +202,11 @@ public abstract class AlfrescoTransactionSupport
      *  
      * @param key the thread resource map key
      * @return Returns a thread resource of null if not present
+     * 
+     * @see TransactionalResourceHelper         for helper methods to create and bind common collection types
      */
-    public static Object getResource(Object key)
+    @SuppressWarnings("unchecked")
+    public static <R extends Object> R getResource(Object key)
     {
         // get the synchronization
         TransactionSynchronizationImpl txnSynch = getSynchronization();
@@ -216,7 +219,7 @@ public abstract class AlfrescoTransactionSupport
                     "   key: " + key + "\n" +
                     "   resource: " + resource);
         }
-        return resource;
+        return (R) resource;
     }
     
     /**

source/java/org/alfresco/repo/transaction/AlfrescoTransactionSupportTest.java

@@ -26,6 +26,7 @@ package org.alfresco.repo.transaction;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
 
 import javax.transaction.UserTransaction;
 
@@ -258,4 +259,23 @@ public class AlfrescoTransactionSupportTest extends TestCase
         checkTxnReadState = transactionService.getRetryingTransactionHelper().doInTransaction(getReadStateWork, false);
         assertEquals("Expected 'read-write transaction'", TxnReadState.TXN_READ_WRITE, checkTxnReadState);
     }
+    
+    public void testResourceHelper() throws Exception
+    {
+        // start a transaction
+        RetryingTransactionCallback<Object> testWork = new RetryingTransactionCallback<Object>()
+        {
+            public Object execute() throws Exception
+            {
+                Map<String, String> map = TransactionalResourceHelper.getMap("abc");
+                assertNotNull("Map not created", map);
+                map.put("1", "ONE");
+                Map<String, String> mapCheck = TransactionalResourceHelper.getMap("abc");
+                assertTrue("Same map not retrieved", map == mapCheck);
+                return null;
+            }
+        };
+        // kick it all off
+        transactionService.getRetryingTransactionHelper().doInTransaction(testWork);
+    }
 }

source/java/org/alfresco/repo/transaction/TransactionalResourceHelper.java

@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2005-2007 Alfresco Software Limited.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+
+ * As a special exception to the terms and conditions of version 2.0 of 
+ * the GPL, you may redistribute this Program in connection with Free/Libre 
+ * and Open Source Software ("FLOSS") applications as described in Alfresco's 
+ * FLOSS exception.  You should have recieved a copy of the text describing 
+ * the FLOSS exception, and it is also available here: 
+ * http://www.alfresco.com/legal/licensing"
+ */
+package org.alfresco.repo.transaction;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * Helper class that will look up or create transactional resources.
+ * This shortcuts some of the "<i>if not existing, then create</i>" code.
+ * 
+ * @author Derek Hulley
+ * @since 3.2
+ */
+public abstract class TransactionalResourceHelper
+{
+    /**
+     * Support method to retrieve or create and bind a <tt>HashMap</tt> to the current transaction.
+     * 
+     * @param <K>           the map key type
+     * @param <V>           the map value type
+     * @param resourceKey   the key under which the resource will be stored
+     * @return              Returns an previously-bound <tt>Map</tt> or else a newly-bound <tt>HashMap</tt>
+     */
+    public static final <K,V> Map<K,V> getMap(Object resourceKey)
+    {
+        Map<K,V> map = AlfrescoTransactionSupport.<Map<K,V>>getResource(resourceKey);
+        if (map == null)
+        {
+            map = new HashMap<K, V>(29);
+            AlfrescoTransactionSupport.bindResource(resourceKey, map);
+        }
+        return map;
+    }
+
+    /**
+     * Support method to retrieve or create and bind a <tt>HashSet</tt> to the current transaction.
+     * 
+     * @param <V>           the set value type
+     * @param resourceKey   the key under which the resource will be stored
+     * @return              Returns an previously-bound <tt>Set</tt> or else a newly-bound <tt>HashSet</tt>
+     */
+    public static final <V> Set<V> getSet(Object resourceKey)
+    {
+        Set<V> set = AlfrescoTransactionSupport.<Set<V>>getResource(resourceKey);
+        if (set == null)
+        {
+            set = new HashSet<V>(29);
+            AlfrescoTransactionSupport.bindResource(resourceKey, set);
+        }
+        return set;
+    }
+
+    /**
+     * Support method to retrieve or create and bind a <tt>ArrayList</tt> to the current transaction.
+     * 
+     * @param <V>           the list value type
+     * @param resourceKey   the key under which the resource will be stored
+     * @return              Returns an previously-bound <tt>List</tt> or else a newly-bound <tt>ArrayList</tt>
+     */
+    public static final <V> List<V> getList(Object resourceKey)
+    {
+        List<V> list = AlfrescoTransactionSupport.<List<V>>getResource(resourceKey);
+        if (list == null)
+        {
+            list = new ArrayList<V>(29);
+            AlfrescoTransactionSupport.bindResource(resourceKey, list);
+        }
+        return list;
+    }
+}