com.ihr.xbrl.manage

Class LockHandler

java.lang.Object

com.ihr.xbrl.manage.LockHandler

public class LockHandler
extends java.lang.Object

Allows to synchronize multiple JVM and avoid deadlocks trying to store the same file in multiple JVMs. The calling pattern is as follows:

 boolean bTryAgain = true;
 while (bTryAgain) {
     bTryAgain = false;
     try {
         LockHandler.withLock(lockCount,session,md5,critical);
     } catch (DeadLockException e) {
         e.checkRaise();
         bTryAgain = true;
     }
 }
 

The critical parameter is an instance of the Callable interface. it is perfectly possible that inside the Callable method a nested call to LockHandler is performed. In that case, take care of using the same lockCount parameter to keep track of the nested calls and recognize how many calls to checkRaise() shall be performed.

Author:

Ignacio

Constructor Summary

Constructors

Constructor and Description
LockHandler()

Method Summary

Modifier and Type	Method and Description
static <T> T	withLock(java.lang.Integer[] lockCount, org.hibernate.Session session, java.lang.String md5, java.util.concurrent.Callable<T> critical) Obtains exclusive access to md5 and executes the critical block of code

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

LockHandler

public LockHandler()

Method Detail

withLock

public static <T> T withLock(java.lang.Integer[] lockCount,
                             org.hibernate.Session session,
                             java.lang.String md5,
                             java.util.concurrent.Callable<T> critical)
                      throws DeadLockException

Obtains exclusive access to md5 and executes the critical block of code

Parameters:

lockCount - is an array of a single integer that will be increased by one on each nested call and decreased by one on each termination. It serves to properly handle DeadLockException

Session - is used to obtain a connection to the database

md5 - this is an MD5 string that identifies the resource to be used as lock token. Two JVMs trying to obtain access to the same resource shall produce the same MD5

the - critical section to be executed

Throws:

DeadLockException - in case this JVM and other JVM have tokens that will produce a deadlock if md5 is obtained by this process