More robust concurrency handling of cached references

git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@2750 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/repo/domain/hibernate/ChildAssocImpl.java

@@ -16,6 +16,10 @@
  */
 package org.alfresco.repo.domain.hibernate;
 
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock.ReadLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock.WriteLock;
+
 import org.alfresco.repo.domain.ChildAssoc;
 import org.alfresco.repo.domain.Node;
 import org.alfresco.service.cmr.repository.ChildAssociationRef;
@@ -34,10 +38,17 @@ public class ChildAssocImpl implements ChildAssoc
     private QName qName;
     private boolean isPrimary;
     private int index;
+    
+    private transient ReadLock refReadLock;
+    private transient WriteLock refWriteLock;
     private transient ChildAssociationRef childAssocRef;
     
     public ChildAssocImpl()
     {
+        ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+        refReadLock = lock.readLock();
+        refWriteLock = lock.writeLock();
+
         setIndex(Integer.MAX_VALUE);              // comes last
     }
 
@@ -64,9 +75,27 @@ public class ChildAssocImpl implements ChildAssoc
         this.getChild().getParentAssocs().remove(this);
     }
     
-    public synchronized ChildAssociationRef getChildAssocRef()
+    public ChildAssociationRef getChildAssocRef()
     {
-        if (childAssocRef == null)
+        // first check if it is available
+        refReadLock.lock();
+        try
+        {
+            if (childAssocRef != null)
+            {
+                return childAssocRef;
+            }
+        }
+        finally
+        {
+            refReadLock.unlock();
+        }
+        // get write lock
+        refWriteLock.lock();
+        try
+        {
+            // double check
+            if (childAssocRef == null )
             {
                 childAssocRef = new ChildAssociationRef(
                         this.typeQName,
@@ -78,6 +107,11 @@ public class ChildAssocImpl implements ChildAssoc
             }
             return childAssocRef;
         }
+        finally
+        {
+            refWriteLock.unlock();
+        }
+    }
 
     public String toString()
     {
@@ -161,6 +195,7 @@ public class ChildAssocImpl implements ChildAssoc
     /**
      * For Hibernate use
      */
+    @SuppressWarnings("unused")
     private void setId(Long id)
     {
         this.id = id;
@@ -175,8 +210,17 @@ public class ChildAssocImpl implements ChildAssoc
      * For Hibernate use
      */
     private void setParent(Node parentNode)
+    {
+        refWriteLock.lock();
+        try
         {
             this.parent = parentNode;
+            this.childAssocRef = null;
+        }
+        finally
+        {
+            refWriteLock.unlock();
+        }
     }
 
     public Node getChild()
@@ -188,8 +232,17 @@ public class ChildAssocImpl implements ChildAssoc
      * For Hibernate use
      */
     private void setChild(Node node)
+    {
+        refWriteLock.lock();
+        try
         {
             child = node;
+            this.childAssocRef = null;
+        }
+        finally
+        {
+            refWriteLock.unlock();
+        }
     }
     
     public QName getTypeQName()
@@ -198,8 +251,17 @@ public class ChildAssocImpl implements ChildAssoc
     }
     
     public void setTypeQName(QName typeQName)
+    {
+        refWriteLock.lock();
+        try
         {
             this.typeQName = typeQName;
+            this.childAssocRef = null;
+        }
+        finally
+        {
+            refWriteLock.unlock();
+        }
     }
     
     public QName getQname()
@@ -208,8 +270,17 @@ public class ChildAssocImpl implements ChildAssoc
     }
 
     public void setQname(QName qname)
+    {
+        refWriteLock.lock();
+        try
         {
             this.qName = qname;
+            this.childAssocRef = null;
+        }
+        finally
+        {
+            refWriteLock.unlock();
+        }
     }
 
     public boolean getIsPrimary()
@@ -218,8 +289,17 @@ public class ChildAssocImpl implements ChildAssoc
     }
 
     public void setIsPrimary(boolean isPrimary)
+    {
+        refWriteLock.lock();
+        try
         {
             this.isPrimary = isPrimary;
+            this.childAssocRef = null;
+        }
+        finally
+        {
+            refWriteLock.unlock();
+        }
     }
 
     public int getIndex()
@@ -228,7 +308,16 @@ public class ChildAssocImpl implements ChildAssoc
     }
 
     public void setIndex(int index)
+    {
+        refWriteLock.lock();
+        try
         {
             this.index = index;
+            this.childAssocRef = null;
+        }
+        finally
+        {
+            refWriteLock.unlock();
+        }
     }
 }

source/java/org/alfresco/repo/domain/hibernate/NodeAssocImpl.java

@@ -16,6 +16,10 @@
  */
 package org.alfresco.repo.domain.hibernate;
 
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock.ReadLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock.WriteLock;
+
 import org.alfresco.repo.domain.Node;
 import org.alfresco.repo.domain.NodeAssoc;
 import org.alfresco.service.cmr.repository.AssociationRef;
@@ -33,10 +37,16 @@ public class NodeAssocImpl implements NodeAssoc
     private Node source;
     private Node target;
     private QName typeQName;
+    
+    private transient ReadLock refReadLock;
+    private transient WriteLock refWriteLock;
     private transient AssociationRef nodeAssocRef;
 
     public NodeAssocImpl()
     {
+        ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+        refReadLock = lock.readLock();
+        refWriteLock = lock.writeLock();
     }
 
     public void buildAssociation(Node sourceNode, Node targetNode)
@@ -62,16 +72,40 @@ public class NodeAssocImpl implements NodeAssoc
         this.getTarget().getSourceNodeAssocs().remove(this);
     }
     
-    public synchronized AssociationRef getNodeAssocRef()
+    public AssociationRef getNodeAssocRef()
     {
-        if (nodeAssocRef == null)
+        // first check if it is available
+        refReadLock.lock();
+        try
         {
-            nodeAssocRef = new AssociationRef(getSource().getNodeRef(),
+            if (nodeAssocRef != null)
+            {
+                return nodeAssocRef;
+            }
+        }
+        finally
+        {
+            refReadLock.unlock();
+        }
+        // get write lock
+        refWriteLock.lock();
+        try
+        {
+            // double check
+            if (nodeAssocRef == null )
+            {
+                nodeAssocRef = new AssociationRef(
+                        getSource().getNodeRef(),
                         this.typeQName,
                         getTarget().getNodeRef());
             }
             return nodeAssocRef;
         }
+        finally
+        {
+            refWriteLock.unlock();
+        }
+    }
 
     public String toString()
     {
@@ -132,8 +166,17 @@ public class NodeAssocImpl implements NodeAssoc
      * For internal use
      */
     private void setSource(Node source)
+    {
+        refWriteLock.lock();
+        try
         {
             this.source = source;
+            this.nodeAssocRef = null;
+        }
+        finally
+        {
+            refWriteLock.unlock();
+        }
     }
 
     public Node getTarget()
@@ -145,8 +188,17 @@ public class NodeAssocImpl implements NodeAssoc
      * For internal use
      */
     private void setTarget(Node target)
+    {
+        refWriteLock.lock();
+        try
         {
             this.target = target;
+            this.nodeAssocRef = null;
+        }
+        finally
+        {
+            refWriteLock.unlock();
+        }
     }
 
     public QName getTypeQName()
@@ -155,7 +207,16 @@ public class NodeAssocImpl implements NodeAssoc
     }
 
     public void setTypeQName(QName typeQName)
+    {
+        refWriteLock.lock();
+        try
         {
             this.typeQName = typeQName;
+            this.nodeAssocRef = null;
+        }
+        finally
+        {
+            refWriteLock.unlock();
+        }
     }
 }