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package com.sun.ejb.containers;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import javax.ejb.ConcurrentAccessException;
import javax.ejb.ConcurrentAccessTimeoutException;
import javax.ejb.IllegalLoopbackException;
import javax.ejb.LockType;
import com.sun.ejb.ComponentContext;
import com.sun.ejb.EjbInvocation;
import com.sun.ejb.InvocationInfo;
import com.sun.ejb.MethodLockInfo;
import com.sun.enterprise.security.SecurityManager;
import org.glassfish.ejb.deployment.descriptor.EjbDescriptor;
/**
* @author Mahesh Kannan
*/
public class CMCSingletonContainer
extends AbstractSingletonContainer {
private final ReentrantReadWriteLock rwLock = new ReentrantReadWriteLock(true);
private final ReentrantReadWriteLock.ReadLock readLock = rwLock.readLock();
private final ReentrantReadWriteLock.WriteLock writeLock = rwLock.writeLock();
private final static long NO_BLOCKING = 0;
private final static long BLOCK_INDEFINITELY = -1;
private final MethodLockInfo defaultMethodLockInfo;
public CMCSingletonContainer(EjbDescriptor desc, ClassLoader cl, SecurityManager sm)
throws Exception {
super(desc, cl, sm);
// In absence of any method lock info default is WRITE lock with no timeout.
defaultMethodLockInfo = new MethodLockInfo();
defaultMethodLockInfo.setLockType(LockType.WRITE);
}
/*
* Findbugs complains that the lock acquired in this method is not
* unlocked on all paths in this method.
*
* Even though the method doesn't unlock the (possibly) acquired
* lock, the lock is guaranteed to be unlocked in releaseContext()
* even in the presence of (both checked and unchecked) exceptions.
*
* The general pattern used by various parts of the EJB container code is:
*
* try {
* container.preInvoke(inv);
* returnValue = container.intercept(inv);
* } catch (Exception1 e1) {
* ...
* } catch (Exception2 e2) {
* ...
* } finally {
* container.postInvoke();
* }
*
* Thus, it is clear that, BaseContainer.postInvoke() which in turn
* calls releaseContext() will be called if container.preInvoke()
* is called. This ensures that CMCSingletonContainer (this class)
* releases the lock acquired by _getContext().
*
* Also, note that the above works even for loopback methods as
* container.preInvoke() and container,postInvoke() will be called
* before every bean method.
*
*/
protected ComponentContext _getContext(EjbInvocation inv) {
checkInit();
InvocationInfo invInfo = inv.invocationInfo;
MethodLockInfo lockInfo = (invInfo.methodLockInfo == null)
? defaultMethodLockInfo : invInfo.methodLockInfo;
Lock theLock = lockInfo.isReadLockedMethod() ? readLock : writeLock;
if ( (rwLock.getReadHoldCount() > 0) &&
(!rwLock.isWriteLockedByCurrentThread()) ) {
if( lockInfo.isWriteLockedMethod() ) {
throw new IllegalLoopbackException("Illegal Reentrant Access : Attempt to make " +
"a loopback call on a Write Lock method '" + invInfo.targetMethod1 +
"' while a Read lock is already held");
}
}
/*
* Please see comment at the beginning of the method.
* Even though the method doesn't unlock the (possibly) acquired
* lock, the lock is guaranteed to be unlocked in releaseContext()
* even if exceptions were thrown in _getContext()
*/
if (!lockInfo.hasTimeout() ||
( (lockInfo.hasTimeout() && (lockInfo.getTimeout() == BLOCK_INDEFINITELY) )) ) {
theLock.lock();
} else {
try {
boolean lockStatus = theLock.tryLock(lockInfo.getTimeout(), lockInfo.getTimeUnit());
if (! lockStatus) {
String msg = "Couldn't acquire a lock within " + lockInfo.getTimeout() +
" " + lockInfo.getTimeUnit();
if( lockInfo.getTimeout() == NO_BLOCKING ) {
throw new ConcurrentAccessException(msg);
} else {
throw new ConcurrentAccessTimeoutException(msg);
}
}
} catch (InterruptedException inEx) {
String msg = "Couldn't acquire a lock within " + lockInfo.getTimeout() +
" " + lockInfo.getTimeUnit();
ConcurrentAccessException cae = (lockInfo.getTimeout() == NO_BLOCKING) ?
new ConcurrentAccessException(msg) : new ConcurrentAccessTimeoutException(msg);
cae.initCause(inEx);
throw cae;
}
}
//Now that we have acquired the lock, remember it
inv.setCMCLock(theLock);
//Now that we have the lock return the singletonCtx
return singletonCtx;
}
/**
* This method must unlock any lock that might have been acquired
* in _getContext().
*
* @see com.sun.ejb.containers.CMCSingletonContainer#_getContext(EjbInvocation inv)
* @param inv The current EjbInvocation that was passed to _getContext()
*/
public void releaseContext(EjbInvocation inv) {
Lock theLock = inv.getCMCLock();
if (theLock != null) {
theLock.unlock();
}
}
}