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package org.apache.avalon.excalibur.concurrent.test;
import junit.framework.TestCase;
import org.apache.avalon.excalibur.concurrent.ReadWriteLock;
/**
* Test harness for the ReadWriteLock.
*
* @author Leo Sutic
*/
public class ReadWriteLockTestCase extends TestCase
{
/**
* Worker thread that attempts to
* aquire a write lock. Start it, wait a little while
* and call the hasSuccess() method.
*/
class TriesWriteLock extends Thread {
protected ReadWriteLock m_lock;
protected boolean m_success = false;
public TriesWriteLock(ReadWriteLock lock)
{
m_lock = lock;
}
public boolean hasSuccess()
{
return m_success;
}
public void run ()
{
try
{
m_lock.aquireWrite();
m_success = true;
}
catch (Exception e)
{
// Ignore. Errors are handled by the testlet
// monitoring hasSuccess().
}
}
}
/**
* Worker thread that attempts to
* aquire a read lock. Start it, wait a little while
* and call the hasSuccess() method.
*/
class TriesReadLock extends Thread {
protected ReadWriteLock m_lock;
protected boolean m_success = false;
public TriesReadLock(ReadWriteLock lock)
{
m_lock = lock;
}
public boolean hasSuccess()
{
return m_success;
}
public void run ()
{
try
{
m_lock.aquireRead();
m_success = true;
}
catch (Exception e)
{
// Ignore. Errors are handled by the testlet
// monitoring hasSuccess().
}
}
}
public ReadWriteLockTestCase (String name) {
super (name);
}
/**
* Attempt to aquire and release read and write locks from
* different threads.
*/
public void testRWLock() throws Exception
{
ReadWriteLock lock = new ReadWriteLock();
TriesReadLock rl = new TriesReadLock(lock);
TriesWriteLock wl = new TriesWriteLock(lock);
rl.start ();
Thread.currentThread().sleep(100);
assertTrue("Attempted to aquire read lock.", rl.hasSuccess ());
wl.start ();
Thread.currentThread().sleep(100);
assertTrue("Attempted to aquire write lock.", !wl.hasSuccess ());
lock.release();
Thread.currentThread().sleep(100);
assertTrue("Attempted to aquire write lock after releasing read lock.", wl.hasSuccess ());
lock.release();
//
// And see that the write lock is released properly.
//
rl = new TriesReadLock(lock);
rl.start ();
Thread.currentThread().sleep(100);
assertTrue("Attempted to aquire read lock.", rl.hasSuccess ());
lock.release();
}
/**
* Test that the lock throws an IllegalStateException when
* one attempts to release an already released lock.
*/
public void testIllegalState () throws Exception
{
ReadWriteLock lock = new ReadWriteLock();
try
{
lock.release();
fail("ReadWriteLock did *not* signal illegal state when an attempt was made to release an unlocked lock.");
}
catch (IllegalStateException ise)
{
// OK, we should receive this one.
}
}
/**
* Tests that attempts to aquire a write lock
* are given higher priority than attempts
* at aquiring a read lock.
*/
public void testMultipleWriters () throws Exception
{
ReadWriteLock lock = new ReadWriteLock();
TriesReadLock rla = new TriesReadLock(lock);
TriesReadLock rlb = new TriesReadLock(lock);
TriesWriteLock wla = new TriesWriteLock(lock);
TriesWriteLock wlb = new TriesWriteLock(lock);
rla.start ();
Thread.currentThread().sleep(100);
assertTrue("Attempted to aquire read lock.", rla.hasSuccess ());
wla.start ();
wlb.start ();
//
// Give the write lock threads some time to attempt
// to aquire a lock.
//
Thread.currentThread().sleep(100);
rlb.start ();
Thread.currentThread().sleep(100);
//
// Two write locks queued up, one read lock queued up.
//
// rla holds read lock
// wlb, wla -> (read lock is held)
// rlb -> (has waiting write locks)
//
assertTrue("Attempted to aquire write lock, and succeeded even though it shouldn't be possible (rla has the lock).", !wla.hasSuccess() && !wlb.hasSuccess() && !rlb.hasSuccess());
//
// Upon releasing the lock, the write lock attempt should succeed, while the read
// lock should still be waiting.
//
lock.release();
Thread.currentThread().sleep(100);
//
// One write lock queued up, one read lock queued up.
//
// wla or wlb holds write lock
// wlb || wla -> (write lock is held)
// rlb -> (has waiting write lock)
//
assertTrue("Attempted to aquire write lock after releasing read lock.", (wla.hasSuccess () || wlb.hasSuccess ()) && !rlb.hasSuccess ()
&& !(wla.hasSuccess () && wlb.hasSuccess ()));
//
// Release write lock again. The other one of wla and wlb should grab the lock.
//
lock.release();
Thread.currentThread().sleep(100);
//
// Two write locks queued up, one read lock queued up.
//
// wla or wlb holds write lock
// rlb -> (write lock is held)
//
assertTrue("Attempted to aquire write lock after releasing read lock.", wla.hasSuccess () && wlb.hasSuccess () && !rlb.hasSuccess ());
//
// Release the lock - the waiting read lock should grab it.
//
lock.release();
Thread.currentThread().sleep(100);
assertTrue("Attempted to aquire write lock after releasing read lock.", wla.hasSuccess () && wlb.hasSuccess () && rlb.hasSuccess ());
}
/**
* Tests that the lock behaves correctly when
* multiple read locks are obtained.
*/
public void testMultipleReaders () throws Exception
{
ReadWriteLock lock = new ReadWriteLock();
TriesReadLock rla = new TriesReadLock(lock);
TriesReadLock rlb = new TriesReadLock(lock);
TriesWriteLock wla = new TriesWriteLock(lock);
rla.start ();
rlb.start ();
Thread.currentThread().sleep(100);
assertTrue("Attempted to aquire read multiple read locks.", rla.hasSuccess () && rlb.hasSuccess ());
wla.start ();
Thread.currentThread().sleep(100);
assertTrue("Write lock aquired even though read locks are held.", !wla.hasSuccess ());
lock.release ();
Thread.currentThread().sleep(100);
assertTrue("Write lock aquired even though read locks are held. (There should be one read lock left)", !wla.hasSuccess ());
lock.release ();
Thread.currentThread().sleep(100);
assertTrue("Write lock not aquired even though lock should be released.", wla.hasSuccess ());
}
/**
* Tests the tryAquireXXX methods.
*/
public void testTrying () throws Exception
{
ReadWriteLock lock = new ReadWriteLock();
TriesReadLock rla = new TriesReadLock(lock);
TriesReadLock rlb = new TriesReadLock(lock);
TriesWriteLock wla = new TriesWriteLock(lock);
TriesWriteLock wlb = new TriesWriteLock(lock);
//
// Grab a read lock, try to aquire one more (should work), and try aquiring a write lock (should not work).
//
rla.start ();
Thread.currentThread().sleep(100);
assertTrue("Could not aquire a read lock.", rla.hasSuccess());
assertTrue("Could not aquire a read lock, even though only a read lock is held.", lock.tryAquireRead());
assertTrue("Could aquire a write lock.", !lock.tryAquireWrite());
//
// Release both locks.
//
lock.release();
lock.release();
//
// Try aquiring a write lock (should work), a read lock (should fail) and another write lock (should fail).
//
assertTrue("Could not aquire a write lock.", lock.tryAquireWrite());
assertTrue("Could aquire a read lock.", !lock.tryAquireRead());
assertTrue("Could aquire a write lock.", !lock.tryAquireWrite());
//
// Release the write lock.
//
lock.release();
assertTrue("Could not aquire a write lock after releasing the lock.", lock.tryAquireWrite());
}
}