facing problem to create folder concurrently in alfresco3.0

[suresheck]

if(todayRef == null)
      {         
         synchronized(this)
         {            
            todayRef = fileFolderService.searchSimple(monthRef, today);         
            if(todayRef == null)
            {            
               todayRef = createNode(monthRef, today, ContentModel.TYPE_FOLDER);            
            }
         }         
      }
Alfresco Version 3.0
This is code of InsertContentWebScript.I have changed this code for synchronization.Two threads are accessing this code concurrently when first thread accessing this todayRef = fileFolderService.searchSimple(monthRef, today);   
then todayRef get null.ok it is first time after then folder of particular day is created.Next time when second thread
is accessing the same todayRef = fileFolderService.searchSimple(monthRef, today);   
It is again giving todayRef null.So can you provide proper solution.Because i am getting exception here.


org.alfresco.service.cmr.repository.DuplicateChildNodeNameException: Duplicate child name not allowed: WFMT_2012_06_27
        at org.alfresco.repo.node.db.hibernate.HibernateNodeDaoServiceImpl.setChildNameUnique(HibernateNodeDaoServiceImpl.java:1294)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:296)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:177)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:144)
        at org.alfresco.repo.transaction.TransactionalDaoInterceptor.invoke(TransactionalDaoInterceptor.java:68)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:166)
        at org.alfresco.repo.domain.hibernate.DirtySessionMethodInterceptor.invoke(DirtySessionMethodInterceptor.java:372)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:166)
        at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
        at $Proxy1.setChildNameUnique(Unknown Source)
        at org.alfresco.repo.node.db.DbNodeServiceImpl.setChildNameUnique(DbNodeServiceImpl.java:2152)
        at org.alfresco.repo.node.db.DbNodeServiceImpl.createNode(DbNodeServiceImpl.java:325)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:296)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:177)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:144)
        at org.alfresco.repo.transaction.SingleEntryTransactionResourceInterceptor.invokeInternal(SingleEntryTransactionResourceInterceptor.java:163)
        at org.alfresco.repo.transaction.SingleEntryTransactionResourceInterceptor.invoke(SingleEntryTransactionResourceInterceptor.java:138)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:166)
        at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
        at $Proxy3.createNode(Unknown Source)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at org.alfresco.repo.service.StoreRedirectorProxyFactory$RedirectorInvocationHandler.invoke(StoreRedirectorProxyFactory.java:221)
        at $Proxy4.createNode(Unknown Source)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:296)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:177)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:144)
        at org.alfresco.repo.node.MLPropertyInterceptor.invoke(MLPropertyInterceptor.java:241)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:166)
        at org.alfresco.repo.node.MLPropertyInterceptor.invoke(MLPropertyInterceptor.java:241)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:166)
        at org.alfresco.repo.node.NodeRefPropertyMethodInterceptor.invoke(NodeRefPropertyMethodInterceptor.java:188)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:166)
        at org.alfresco.repo.tenant.MultiTNodeServiceInterceptor.invoke(MultiTNodeServiceInterceptor.java:108)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:166)
        at org.alfresco.repo.node.NodeRefPropertyMethodInterceptor.invoke(NodeRefPropertyMethodInterceptor.java:188)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:166)
        at org.alfresco.repo.tenant.MultiTNodeServiceInterceptor.invoke(MultiTNodeServiceInterceptor.java:108)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:166)
        at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
        at $Proxy3.createNode(Unknown Source)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:296)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:177)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:144)
        at net.sf.acegisecurity.intercept.method.aopalliance.MethodSecurityInterceptor.invoke(MethodSecurityInterceptor.java:80)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:166)
        at org.alfresco.repo.security.permissions.impl.ExceptionTranslatorMethodInterceptor.invoke(ExceptionTranslatorMethodInterceptor.java:49)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:166)
        at org.alfresco.repo.audit.AuditComponentImpl.audit(AuditComponentImpl.java:245)
        at org.alfresco.repo.audit.AuditMethodInterceptor.invoke(AuditMethodInterceptor.java:69)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:166)
        at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:107)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:166)
        at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
        at $Proxy3.createNode(Unknown Source)
        at com.bt.wfmt.dms.alfresco.webscripts.InsertContentWebScript.createNode(InsertContentWebScript.java:278)
        at com.bt.wfmt.dms.alfresco.webscripts.InsertContentWebScript.getDocumentFolder(InsertContentWebScript.java:248)
        at com.bt.wfmt.dms.alfresco.webscripts.InsertContentWebScript.execute(InsertContentWebScript.java:75)
        at org.alfresco.repo.web.scripts.RepositoryContainer$1.execute(RepositoryContainer.java:309)
        at org.alfresco.repo.transaction.RetryingTransactionHelper.doInTransaction(RetryingTransactionHelper.java:294)
        at org.alfresco.repo.transaction.RetryingTransactionHelper.doInTransaction(RetryingTransactionHelper.java:209)
        at org.alfresco.repo.web.scripts.RepositoryContainer.transactionedExecute(RepositoryContainer.java:320)
        at org.alfresco.repo.web.scripts.RepositoryContainer.executeScript(RepositoryContainer.java:264)
        at org.alfresco.web.scripts.AbstractRuntime.executeScript(AbstractRuntime.java:240)
        at org.alfresco.web.scripts.AbstractRuntime.executeScript(AbstractRuntime.java:139)
        at org.alfresco.web.scripts.servlet.WebScriptServlet.service(WebScriptServlet.java:116)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
        at org.alfresco.web.app.servlet.MTWebScriptAuthenticationFilter.doFilter(MTWebScriptAuthenticationFilter.java:102)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:870)
        at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
        at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
        at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
        at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:685)
        at java.lang.Thread.run(Unknown Source)

[bisana]

For others to help, it will be good if you can explain your problem
Also please use code tag to display your error message and codes
thanks
Joseph John

[mrogers]

And what is the value of "this" i.e. which object are you synchronizing on?

[mrogers]

If your code is in a retrying transaction then it will work.   No need for the sync which is dangerous.

The duplicate create will fail.  And then the next tran will see the folder exists and carry on.

[suresheck]

And what is the value of "this" i.e. which object are you synchronizing on?

Here this is the current object of InsertContentWebScript.

synchronized(this)
         {            
            todayRef = fileFolderService.searchSimple(monthRef, today);         
            if(todayRef == null)
            {            
               todayRef = createNode(monthRef, today, ContentModel.TYPE_FOLDER);            
            }
         }   
Here first time when one client code access the todayRef.It gives todayRef = null and at the same time concurrently when sencond client code access this todayRef it gives again null.So it again call this createNode method.So gives exception.

org.alfresco.service.cmr.repository.DuplicateChildNodeNameException: Duplicate child name not allowed: WFMT_2012_06_27
        at org.alfresco.repo.node.db.hibernate.HibernateNodeDaoServiceImpl.setChildNameUnique(HibernateNodeDaoServiceImpl.java:1294)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)