ALF-19779: Stack specific: Caches are no synchronized between the nodes

git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@54391 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/repo/cache/DefaultSimpleCache.java

@@ -95,9 +95,20 @@ public final class DefaultSimpleCache<K extends Serializable, V extends Object>
 
     @Override
     public void put(K key, V value)
+    {
+        putAndCheckUpdate(key, value);
+    }
+
+    /**
+     * <code>put</code> method that may be used to check for updates in a thread-safe manner.
+     * 
+     * @return <code>true</code> if the put resulted in a change in value, <code>false</code> otherwise.
+     */
+    public boolean putAndCheckUpdate(K key, V value)
     {
         AbstractMap.SimpleImmutableEntry<K, V> kvp = new AbstractMap.SimpleImmutableEntry<K, V>(key, value);
-        map.put(key, kvp);
+        AbstractMap.SimpleImmutableEntry<K, V> priorKVP = map.put(key, kvp);
+        return priorKVP != null && (! priorKVP.equals(kvp));
     }
     
     @Override

source/test-java/org/alfresco/repo/cache/DefaultSimpleCacheTest.java

@@ -62,4 +62,43 @@ public class DefaultSimpleCacheTest extends SimpleCacheTestBase<DefaultSimpleCac
         assertEquals("4", cache.get(4));
         assertEquals("5", cache.get(5));
     }
+    
+    @Test
+    public void putAndCheckUpdate()
+    {
+        // Put an initial value
+        cache.put(101, "101");
+        // Update it
+        assertEquals(true, cache.putAndCheckUpdate(101, "99101"));
+        // Check the value really was updated
+        assertEquals("99101", cache.get(101));
+        
+        // Precondition: no value for key 102
+        assertFalse(cache.contains(102));
+        // Put a value - and test the return
+        assertEquals(false, cache.putAndCheckUpdate(102, "102"));
+        assertEquals("102", cache.get(102));
+        
+        cache.put(103, null);
+        assertEquals(true, cache.putAndCheckUpdate(103, "103"));
+        // Repeat the put, this should not be an update
+        assertEquals(false, cache.putAndCheckUpdate(103, "103"));
+        
+        assertFalse(cache.contains(104));
+        assertEquals(false, cache.putAndCheckUpdate(104, null));
+        // Repeat putting null - still not an update, as we had that value a moment ago.
+        assertEquals(false, cache.putAndCheckUpdate(104, null));
+        // Now an update
+        assertEquals(true, cache.putAndCheckUpdate(104, "104"));
+        // Another update
+        assertEquals(true, cache.putAndCheckUpdate(104, "99104"));
+        // Another update, back to null
+        assertEquals(true, cache.putAndCheckUpdate(104, null));
+        // Not an update - still null
+        assertEquals(false, cache.putAndCheckUpdate(104, null));
+        
+        cache.remove(104);
+        assertEquals(false, cache.putAndCheckUpdate(104, "104"));
+        assertEquals(true, cache.putAndCheckUpdate(104, null));
+    }
 }