[JCR-2874] Locked helper class improvements

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Component/s: jackrabbit-jcr-commons, jackrabbit-spi-commons
• Assignee: Unassigned
• Reporter: Alex Deparvu
• Created: 02/Feb/11 15:19
• Updated: 04/Mar/11 14:54

Description

Currently there are 2 helper classes called Locked, that serve the same purpose:

one in jcr-commons http://jackrabbit.apache.org/api/2.2/org/apache/jackrabbit/util/Locked.html
and the other one in spi-commons http://jackrabbit.apache.org/api/2.2/org/apache/jackrabbit/spi/commons/lock/Locked.html

There was a discussion a while back about deprecating one of them. the issue affected JR 1.4 and it is now closed. I guess the old patches have not been applied: https://issues.apache.org/jira/browse/JCR-1169

Anyway, I propose to keep the one in jcr-commons and deprecate the other one.

Also, while we are on the matter, I'd like to propose some improvements to this class:

1. make the lock configurable, basically add a flag to say if it is session scoped or not (currently it is hard coded as a session wide lock).

2. upgrade the lock code to use the LockManager (http://www.day.com/maven/javax.jcr/javadocs/jcr-2.0/javax/jcr/lock/LockManager.html) - this means that the class will rely only on the JCR 2.0. this is a potentially breaking change, although a lot of the classes in this module depend directly on the 2.0 API

3. allow the Locked class to use generics. The biggest issue here is the timeout behavior: on timeout you get the TIMED_OUT token object, and you have to compare the response to that, to make sure that the code ran properly. I think the simplest solution would be to not touch the class directly and build a wrapper class that is generified, and throws a RepositoryException in case of a timeout.

This would turn this code( from the javadoc)

Node counter = ...;
Object ret = new Locked() {
protected Object run(Node counter) throws RepositoryException

{ ... }
}.with(counter, false);
if (ret == Locked.TIMED_OUT) { // do whatever you think is appropriate in this case } else { // get the value long nextValue = ((Long) ret).longValue(); }

into

Node counter = ...;
Long ret = new LockedWrapper<Long>() {
protected Object run(Node counter) throws RepositoryException { ... }

}.with(counter, false);

// handle the timeout as a RepositoryException

4. lock tests location? (this is more of an observation than an actual issue it came to me via 'find . -name *Lock*Test.java')

There are some lock tests in jackrabbit-core:

• jackrabbit-core/src/test/java/org/apache/jackrabbit/core/LockTest.java
• jackrabbit-core/src/test/java/org/apache/jackrabbit/core/lock/LockTimeoutTest.java
• jackrabbit-core/src/test/java/org/apache/jackrabbit/core/lock/ConcurrentLockingWithTransactionsTest.java
• jackrabbit-core/src/test/java/org/apache/jackrabbit/core/lock/ExtendedLockingTest.java
• jackrabbit-core/src/test/java/org/apache/jackrabbit/core/lock/ConcurrentLockingTest.java

...some in jackrabbit-jcr2spi:

• jackrabbit-jcr2spi/src/test/java/org/apache/jackrabbit/jcr2spi/lock/OpenScopedLockTest.java
• jackrabbit-jcr2spi/src/test/java/org/apache/jackrabbit/jcr2spi/lock/SessionScopedLockTest.java
• jackrabbit-jcr2spi/src/test/java/org/apache/jackrabbit/jcr2spi/lock/DeepLockTest.java
• jackrabbit-jcr2spi/src/test/java/org/apache/jackrabbit/jcr2spi/lock/AbstractLockTest.java

and others in jackrabbit-jcr-tests:

• jackrabbit-jcr-tests/src/main/java/org/apache/jackrabbit/test/api/observation/LockingTest.java
• jackrabbit-jcr-tests/src/main/java/org/apache/jackrabbit/test/api/lock/SetValueLockExceptionTest.java
• jackrabbit-jcr-tests/src/main/java/org/apache/jackrabbit/test/api/lock/LockManagerTest.java
• jackrabbit-jcr-tests/src/main/java/org/apache/jackrabbit/test/api/lock/OpenScopedLockTest.java
• jackrabbit-jcr-tests/src/main/java/org/apache/jackrabbit/test/api/lock/LockTest.java
• jackrabbit-jcr-tests/src/main/java/org/apache/jackrabbit/test/api/lock/SessionScopedLockTest.java
• jackrabbit-jcr-tests/src/main/java/org/apache/jackrabbit/test/api/lock/DeepLockTest.java
• jackrabbit-jcr-tests/src/main/java/org/apache/jackrabbit/test/api/lock/AbstractLockTest.java

I'd like to move this one: org.apache.jackrabbit.core.LockTest from the jackrabbit-core to the jackrabbit-jcr-commons where the implementation class lives.

I'll add a patch for 1 & 2, but the rest I need your opinion.