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From Oliver Zeigermann <oliver.zeigerm...@gmail.com>
Subject Re: Transaction API, ReadWriteLock
Date Wed, 06 Jul 2005 14:14:22 GMT
By the way, when giving me first advice I stumbled over exactly this
difference between the lock manager and the lock itself...

Oliver

On 7/6/05, Oliver Zeigermann <oliver.zeigermann@gmail.com> wrote:
> You are right, but only for the lock manager. The lock manager takes
> care of uniquely mapping a resource id to a lock, but when you work on
> a lock *directly* it must - of course - be the same object.
> 
> Oliver
> 
> On 7/6/05, Aaron Hamid <arh14@cornell.edu> wrote:
> > Is this true?  It was my impression, have first written such a class, and then finding
and skimming the javadoc for [ReadWrite]LockManager, and particularly 'getLock' and 'createLock',
that lock singletons would be automatically created and managed.  Otherwise the developer
must write a lot of boilerplate code for keeping a singleton map of locks.  Surely only the
'resourceId' must be the same, and not the actual ReadWriteLock reference?
> >
> > LockManager: "Encapsulates creation, removal, and retrieval of locks. Each resource
can have at most a single lock."
> >
> > Aaron
> >
> > Oliver Zeigermann wrote:
> > > Ooops, sorry, you are right. Not only the resource Id, but the lock
> > > *itself* must be the same in both threads.
> > >
> > > Doing it this way:
> > >
> > >               final ReadWriteLock fileLock = new ReadWriteLock("Huhu", loggerFacade);
> > >               Runnable run = new Runnable() {
> > >
> > >                       public void run() {
> > >
> > >                               try {
> > >                                       System.out.println("before acquiring
a lock "
> > >                                                       + Thread.currentThread());
> > >                                       boolean result = fileLock.acquireWrite(Thread
> > >                                                       .currentThread(), Long.MAX_VALUE);
> > >                                       System.out.println("lock result: " +
result + " "
> > >                                                       + Thread.currentThread());
> > >                                       Thread.sleep(20000);
> > >                                       System.out.println("after sleeping "
> > >                                                       + Thread.currentThread());
> > >                               } catch (InterruptedException e) {
> > >                                       e.printStackTrace(System.err);
> > >
> > >                               } finally {
> > >                                       fileLock.release(Thread.currentThread());
> > >                               }
> > >                       }
> > >
> > >               };
> > >
> > >               Thread t1 = new Thread(run, "Thread1");
> > >               Thread t2 = new Thread(run, "Thread2");
> > >               t1.start();
> > >               try {
> > >                       Thread.sleep(1000);
> > >               } catch (InterruptedException e) {
> > >               }
> > >               t2.start();
> > >
> > >
> > > works fine for me.
> > >
> > > HTH
> > >
> > > Oliver
> > >
> > > On 7/6/05, LeRoy.Yanta@securian.com <LeRoy.Yanta@securian.com> wrote:
> > >
> > >>
> > >>
> > >>
> > >>
> > >>Oliver,
> > >>
> > >>I tried your suggestion by changing my ReadWriteLock statement to
> > >>
> > >>ReadWriteLock fileLock = new ReadWriteLock("c:/logRec.txt",loggerFacade);
> > >>
> > >>However, I received the same results as when I used new File(..).
> > >>
> > >>LeRoy
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>             Oliver Zeigermann
> > >>             <oliver.zeigerman
> > >>             n@gmail.com>                                           
   To
> > >>                                       Jakarta Commons Users List
> > >>             07/06/2005 01:44          <commons-user@jakarta.apache.org>
> > >>             AM                                                        
cc
> > >>
> > >>                                                                   Subject
> > >>             Please respond to         Re: Transaction API, ReadWriteLock
> > >>             "Jakarta Commons
> > >>                Users List"
> > >>             <commons-user@jak
> > >>             arta.apache.org>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>Most likely your problem ist that new File(..) creates different
> > >>objects in each thread. I would try using something like the path to
> > >>the file as String.
> > >>
> > >>Oliver
> > >>
> > >>On 7/5/05, LeRoy.Yanta@securian.com <LeRoy.Yanta@securian.com> wrote:
> > >>
> > >>>
> > >>>
> > >>>
> > >>>I'm trying to use the ReadWriteLock class to acquire a write lock on
a
> > >>
> > >>file
> > >>
> > >>>in a servlet.  When I generate multiple threads of the servlet using
a
> > >>
> > >>WTE
> > >>
> > >>>5.1 server in the WSAD 5.1 IDE, I'm not able to get ReadWriteLock to
> > >>
> > >>block
> > >>
> > >>>other servlet threads after the first servlet thread obtains the lock.
> > >>
> > >>I'm
> > >>
> > >>>using two IE browser windows to generate the two servlet threads.  Below
> > >>
> > >>is
> > >>
> > >>>ReadWriteLock code I have in the servlet followed by the
> > >>
> > >>System.out.println
> > >>
> > >>>statements that are generated in the server log file during my test.
> > >>>
> > >>>ReadWriteLock fileLock = new ReadWriteLock(new File(c:/logRec.txt,
> > >>>loggerFacade);
> > >>>try {
> > >>>      System.out.println("before acquiring a lock " +
> > >>>Thread.currentThread());
> > >>>      boolean result =
> > >>>fileLock.acquireWrite(Thread.currentThread(),Long.MAX_VALUE);
> > >>>      System.out.println("lock result: " + result + " " +
> > >>>Thread.currentThread());
> > >>>      Thread.sleep(20000);
> > >>>      System.out.println("after sleeping " + Thread.currentThread());
> > >>>      FileWriter recFile = new FileWriter(c:/logRec.txt, true);
> > >>>      recFile.write("text from testFileTran");
> > >>>      recFile.close();
> > >>>} catch (InterruptedException e) {
> > >>>      e.printStackTrace(System.err);
> > >>>
> > >>>} catch (IOException e) {
> > >>>      e.printStackTrace(System.err);
> > >>>
> > >>>} finally {
> > >>>      fileLock.release(Thread.currentThread());
> > >>>}
> > >>>
> > >>>[7/5/05 8:26:03:326 CDT]  7c1477e SystemOut     O before acquiring a
lock
> > >>>Thread[Servlet.Engine.Transports : 0,5,main]
> > >>>[7/5/05 8:26:03:326 CDT]  7c1477e SystemOut     O lock result: true
> > >>>Thread[Servlet.Engine.Transports : 0,5,main]
> > >>>[7/5/05 8:26:08:384 CDT] 24c3477d SystemOut     O before acquiring a
lock
> > >>>Thread[Servlet.Engine.Transports : 1,5,main]
> > >>>[7/5/05 8:26:08:384 CDT] 24c3477d SystemOut     O lock result: true
> > >>>Thread[Servlet.Engine.Transports : 1,5,main]
> > >>>[7/5/05 8:26:23:335 CDT]  7c1477e SystemOut     O after sleeping
> > >>>Thread[Servlet.Engine.Transports : 0,5,main]
> > >>>[7/5/05 8:26:28:382 CDT] 24c3477d SystemOut     O after sleeping
> > >>>Thread[Servlet.Engine.Transports : 1,5,main]
> > >>>
> > >>>
> > >>>From reviewing the Transaction documentation and mailing list archives,
> > >>
> > >>I'm
> > >>
> > >>>not able to determine what I'm doing wrong.
> > >>>
> > >>>
> > >>>---------------------------------------------------------------------
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> > >>>
> > >>>
> > >>
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> > >>
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> > >>
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> > >
> > >
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