Re: Jackrabbit, JCA, JBoss, EJB and transactions

Thu, 12 Aug 2010 09:15:40 -0700 

Hello,
please don't mind, but I have to bring this up again... I'm still looking into this problem. My question now is: When two users have two sessions in use concurrently, what exactly happens once one of the users makes a Workspace-Write? I guess the session of the other user gets updated somehow, correct? Can anyone hint me to the java-class or part of Jackrabbit that is responsible for synchronizing the sessions? 

Thanks
Dominik

Am 06.08.2010 16:38, schrieb Dominik Klaholt:

I have simplified the test-case that shows the - in my opinion - 
questionalbe behavior. Now it's without the confusing EJB stuff - just 
Jackrabbit and transactions. Any thoughts?


        /**

         * The following test-case works, IF step 1 is done without 
being encapsulated in a transaction (just remove the

         * utx-lines in step 1 and add the 's1.logout()')
         */
        String id;
        InitialContext jndiContext = new InitialContext();
        rep = (Repository) jndiContext.lookup("java:/jcr/local");

        // Step 1: user 1 acquires session and writes, then logs out
        utx = (UserTransaction) jndiContext.lookup("UserTransaction");
        utx.begin();

        Session s1 = rep.login(new SimpleCredentials(USER1, 
USER1.toCharArray()));

        Node nodeBys1 = s1.getRootNode().addNode("aNode");
        nodeBys1.setProperty("aProperty", USER1);
        s1.save();
        id = nodeBys1.getIdentifier();
        // s1.logout();
        utx.commit();


        // Step 2: user 2 acquires session, alters value written by 
user 1, then logs out

        utx = (UserTransaction) jndiContext.lookup("UserTransaction");
        utx.begin();

        Session s2 = rep.login(new SimpleCredentials(USER2, 
USER2.toCharArray()));

        s2.getNodeByIdentifier(id).setProperty("aProperty", USER2);
        s2.save();
        utx.commit();


        // Step 3: user 1 acquires session again, reads the property 
altered by user 2... but does not read the correct

        // value
        utx = (UserTransaction) jndiContext.lookup("UserTransaction");
        utx.begin();

        Session s = rep.login(new SimpleCredentials(USER1, 
USER1.toCharArray()));
        AssertJUnit.assertEquals(USER2, 
s.getNodeByIdentifier(id).getProperty("aProperty").getString());

        utx.commit();


Am 06.08.2010 02:19, schrieb Dominik Klaholt:

Hello,


i have a problem using jackrabbit with EJB transactions. I will try 
to explain what i have done and understood so far. Any corrections 
are really welcome.
I am using Jackrabbit 2.1.0 within JBoss 5.1.0 as a XA-datasource by 
help of the JCA adapter that is provided by Jackrabbit. My jcr-ds.xml 
contains the flags



<config-property name="bindSessionToTransaction" 
type="java.lang.Boolean">true</config-property>


and

<application-managed-security/>


so that the JCA-session-handles are bound to the container/bean 
managed transactions and the actual JCR sessions within the JCA 
connection pool are

distinguished by the parameters of the 'repository.login()' calls.

The following test-case works fine:

(1)Repository rep = (Repository) jndiContext.lookup("java:/jcr/local");

    Session s1 = rep.login(new SimpleCredentials(USER1, 
USER1.toCharArray()));

    Node nodeBys1 = s1.getRootNode().addNode("aNode");
    nodeBys1.setProperty("aProperty", USER1);
    s1.save();
    String id = nodeBys1.getIdentifier();
    s1.logout();


(2)Session s2 = rep.login(new SimpleCredentials(USER2, 
USER2.toCharArray()));

    s2.getNodeByIdentifier(id).setProperty("aProperty", USER2);
    s2.save();
    s2.logout();


(3)Session s1 = rep.login(new SimpleCredentials(USER1, 
USER1.toCharArray()));
    AssertJUnit.assertEquals(USER2, 
s1.getNodeByIdentifier(id).getProperty("aProperty").getString());



(1) User 1 logs in and creates a node with a property. (2) Then user 
2 logs in and alters the property of the
newly created node. (3) Finally user 1 logs in again and reads the 
property. He reads the value user 2 has written.



Now, i want to encapsulate each of these three steps in one method of 
a Stateless Session Bean. E.g. (1) looks like this:


    public String createNode(String username) throws Exception {
        InitialContext jndiContext = new InitialContext();

        Repository rep = (Repository) 
jndiContext.lookup("java:/jcr/local");
        Session s = rep.login(new SimpleCredentials(username, 
username.toCharArray()));

        Node node = s.getRootNode().addNode("aNode");
        node.setProperty("aProperty", username);
        s.save();
        return node.getIdentifier();
    }


Note, that this method will automatically be encapsulated by a 
container managed transaction. And due to the 
bindSessionToTransaction-flag in the jcr-ds.xml, the
JCASessionHandle used within the container managed transaction will 
be automatically closed once the transaction commits (the 
JCASessionHandle will be closed, the

associated JCR session stays alive within the JCA connection pool).

The above mentioned 3 steps of the simple test-case can now be 
expressed as a sequence of method-calls of the stateless EJB:



(1)jcrTest = (JCRTestBeanLocal) 
jndiContext.lookup("test/JCRTestBean/local");

    id = jcrTest.createNode(USER1);

(2)jcrTest.alterProperty(id, USER2, USER2);

(3)AssertJUnit.assertEquals(USER2, jcrTest.getProperty(id, USER1))


However, this test-case fails, as in step (3) user 1 does not read 
the changes committed by user 2. Interestingly the test-case passes 
once i deactivate transaction

support for step (1):

    @TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED)
    public String createNode(String username) throws Exception {...}


Does anyone know what i could do to make the test-case pass without 
deactivating transaction support?

Any hints would be really, really appreciated.

Best regards,
Dominik


Below are the EJB-methods for the steps (2) and (3):


    public void alterProperty(String id, String newValue, String 
username) throws Exception {

        InitialContext jndiContext = new InitialContext();

        Repository rep = (Repository) 
jndiContext.lookup("java:/jcr/local");
        Session s = rep.login(new SimpleCredentials(username, 
username.toCharArray()));

        s.getNodeByIdentifier(id).setProperty("aProperty", newValue);
        s.save();
    }


    public String getProperty(String id, String username) throws 
Exception {

        InitialContext jndiContext = new InitialContext();

        Repository rep = (Repository) 
jndiContext.lookup("java:/jcr/local");
        Session s = rep.login(new SimpleCredentials(username, 
username.toCharArray()));
        return 
s.getNodeByIdentifier(id).getProperty("aProperty").getString();

    }
























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