Merged BRANCHES/DEV/mward/cifs_hazelcast_conf to HEAD:

36500: ALF-13821: CIFS and WebDAV should use same Hazelcast configuration mechanism
   36507: ALF-13821: CIFS and WebDAV should use same Hazelcast configuration mechanism
   36511: ALF-13821: CIFS and WebDAV should use same Hazelcast configuration mechanism
   36519: ALF-13821: Extract hazelcastConfig, hazelcastInstanceFactory bean definitions from webdav-context.xml to cluster-context.xml
   36553: ALF-13821: CIFS and WebDAV should use same Hazelcast configuration mechanism

git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@36581 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/repo/cluster/HazelcastInstanceFactory.java

@@ -18,34 +18,122 @@
  */
 package org.alfresco.repo.cluster;
 
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+
+import org.alfresco.util.PropertyCheck;
+
 import com.hazelcast.config.Config;
 import com.hazelcast.core.Hazelcast;
 import com.hazelcast.core.HazelcastInstance;
 
 /**
  * Provides a way of lazily creating HazelcastInstances for a given configuration.
- * The HazelcastInstance will not be created until {@link #newInstance()} is called.
+ * The HazelcastInstance will not be created until {@link #getInstance()} is called.
  * <p>
  * An intermediary class such as this is required in order to avoid starting
  * Hazelcast instances when clustering is not configured/required. Otherwise
  * simply by defining a HazelcastInstance bean clustering would spring into life.
+ * <p>
+ * Please note this class provides non-static access deliberately, and should be
+ * injected into any clients that require its services.
  * 
  * @author Matt Ward
  */
 public class HazelcastInstanceFactory
 {
-    public Config config;
-
-    public HazelcastInstance newInstance()
+    private Config config;
+    private HazelcastInstance hazelcastInstance;
+    /** Guards {@link #config} and {@link #hazelcastInstance} */
+    private ReentrantReadWriteLock rwLock = new ReentrantReadWriteLock();
+    
+    public HazelcastInstance getInstance()
     {
-        return Hazelcast.newHazelcastInstance(config);
+        rwLock.readLock().lock();
+        try
+        {
+            if (hazelcastInstance != null)
+            {
+                return hazelcastInstance;
+            }
+        }
+        finally
+        {
+            rwLock.readLock().unlock();
+        }
+        
+        // hazelcastInstance is null, so create it.
+        rwLock.writeLock().lock();
+        try
+        {
+            // Double check condition hasn't changed in between locks.
+            if (hazelcastInstance == null)
+            {
+                hazelcastInstance = Hazelcast.newHazelcastInstance(config);
+            }
+            return hazelcastInstance;
+        }
+        finally
+        {
+            rwLock.writeLock().unlock();
+        }
     }
 
     /**
-     * @param config the config to set
+     * Checks whether hazelcast has been given a valid cluster name. If so,
+     * then clustering is considered enabled. This condition should be checked
+     * before calling {@link #getInstance()}.
+     * 
+     * @return true if clustering is enabled, false otherwise.
+     */
+    public boolean isClusteringEnabled()
+    {
+        rwLock.readLock().lock();
+        try
+        {
+            String clusterName = config.getGroupConfig().getName();
+            return (PropertyCheck.isValidPropertyString(clusterName));
+        }
+        finally
+        {
+            rwLock.readLock().unlock();
+        }
+    }
+    
+    /**
+     * Retrieve the name of the cluster for the configuration used by this factory.
+     * 
+     * @return String - the cluster name.
+     */
+    public String getClusterName()
+    {
+        rwLock.readLock().lock();
+        try
+        {
+            String clusterName = config.getGroupConfig().getName();
+            return clusterName;
+        }
+        finally
+        {
+            rwLock.readLock().unlock();
+        }
+    }
+    
+    /**
+     * Sets the Hazelcast configuration that will be used by this factory when
+     * creating the HazelcastInstance.
+     * 
+     * @param config Hazelcast configuration
      */
     public void setConfig(Config config)
     {
-        this.config = config;
+        rwLock.writeLock().lock();
+        try
+        {
+            this.config = config;
+        }
+        finally
+        {
+            rwLock.writeLock().unlock();
+        }
     }
 }