org.apache.lucene.store
Class Lock

java.lang.Object
  extended byorg.apache.lucene.store.Lock

public abstract class Lock
extends Object

An interprocess mutex lock.

Typical use might look like:

 new Lock.With(directory.makeLock("my.lock")) {
     public Object doBody() {
       ... code to execute while locked ...
     }
   }.run();
 

Version:
$Id: Lock.java 472959 2006-11-09 16:21:50Z yonik $
Author:
Doug Cutting
See Also:
Directory.makeLock(String)

Nested Class Summary
static class Lock.With
          Utility class for executing code with exclusive access.
 
Field Summary
protected  Throwable failureReason
          If a lock obtain called, this failureReason may be set with the "root cause" Exception as to why the lock was not obtained.
static long LOCK_POLL_INTERVAL
           
 
Constructor Summary
Lock()
           
 
Method Summary
abstract  boolean isLocked()
          Returns true if the resource is currently locked.
abstract  boolean obtain()
          Attempts to obtain exclusive access and immediately return upon success or failure.
 boolean obtain(long lockWaitTimeout)
          Attempts to obtain an exclusive lock within amount of time given.
abstract  void release()
          Releases exclusive access.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

LOCK_POLL_INTERVAL

public static long LOCK_POLL_INTERVAL

failureReason

protected Throwable failureReason
If a lock obtain called, this failureReason may be set with the "root cause" Exception as to why the lock was not obtained.

Constructor Detail

Lock

public Lock()
Method Detail

obtain

public abstract boolean obtain()
                        throws IOException
Attempts to obtain exclusive access and immediately return upon success or failure.

Returns:
true iff exclusive access is obtained
Throws:
IOException

obtain

public boolean obtain(long lockWaitTimeout)
               throws IOException
Attempts to obtain an exclusive lock within amount of time given. Currently polls once per second until lockWaitTimeout is passed.

Parameters:
lockWaitTimeout - length of time to wait in ms
Returns:
true if lock was obtained
Throws:
IOException - if lock wait times out or obtain() throws an IOException

release

public abstract void release()
Releases exclusive access.


isLocked

public abstract boolean isLocked()
Returns true if the resource is currently locked. Note that one must still call obtain() before using the resource.



Copyright © 2000-2008 Apache Software Foundation. All Rights Reserved.