Re: Item cannot be saved because it has been modified externally: node /

[François Cassistat]

I've managed to make some basic case that throws the error every time.

import org.apache.jackrabbit.core.TransientRepository;

import javax.jcr.*;

public class JCRConcurrency
{
    public static void main(String[] args) throws RepositoryException
    {
        Repository repo;
        if (args.length >= 2)
            repo = new TransientRepository(args[0], args[1]);
        else
            repo = new TransientRepository();
        SimpleCredentials simpleCredentials = new SimpleCredentials("username", 
"password".toCharArray());
        Session sessionInit = repo.login(simpleCredentials);

        // initialization
        Node root = sessionInit.getRootNode();
        Node test;
        if (root.hasNode("test"))
            test = root.getNode("test");
        else
            test = root.addNode("test");
        if (!test.hasProperty("property"))
            test.setProperty("property", 0);
        sessionInit.save();
        String testIdentifier = test.getIdentifier();

        // session 1
        Session session1 = repo.login(simpleCredentials);
        Node test1 = session1.getNodeByIdentifier(testIdentifier);
        System.out.println(test1.getProperty("property").getLong());
        test1.setProperty("property", 1);

        // session 2 is doing some other things at the same time
        Session session2 = repo.login(simpleCredentials);
        Node test2 = session2.getNodeByIdentifier(testIdentifier);
        test2.setProperty("property", 2);

        // session 2 saves first
        session2.save();
        session2.logout();

        // session 1 saves
        session1.save();
        session1.logout();

        sessionInit.logout();

        System.exit(0);
    }
}




Le 2010-12-10 à 6:12 PM, François Cassistat a écrit :

> Hi list !
> 
> I've got some concurrency problem while saving. My application use distinct 
> Sessions object and when two processes are trying to modify the same property 
> of the same node at the same time. I've get the exception below :
> javax.jcr.InvalidItemStateException: Item cannot be saved because it has been 
> modified externally: node /
>        at 
> org.apache.jackrabbit.core.ItemImpl.getTransientStates(ItemImpl.java:249)
>        at org.apache.jackrabbit.core.ItemImpl.save(ItemImpl.java:981)
>        at org.apache.jackrabbit.core.SessionImpl.save(SessionImpl.java:920)
>        at com.myproject.MyProject.save(MyProject.java:1525)
>        ...
> 
> 
> I have tried saving this way :
> synchronized (this)
> {
>    session.refresh(true);
>    session.save();
> }
> 
> 
> Is there any way around or only locks and transactions can prevent that ?
> 
> 
> Thanks !
> 
> 
> François
>