To prevent locks from being held for excessive amounts of time when
a LockTimeoutException exception or a LockDeadlockException exception
occurs, your application must catch unexpected exceptions and call
the rollback method when an unexpected event occurs.
Procedure
- Catch the exception, and display resulting message.
try {
...
} catch (ObjectGridException oe) {
System.out.println(oe);
}
The following exception displays as a result:
com.ibm.websphere.objectgrid.plugins.LockDeadlockException: Message
This message represents the string that
is passed as a parameter when the exception is created and thrown.
- Roll back the transaction after an exception:
Session sess = ...;
ObjectMap person = sess.getMap("PERSON");
boolean activeTran = false;
try
{
sess.begin();
activeTran = true;
Person p = (IPerson)person.get("Lynn");
// Lynn had a birthday, so we make her 1 year older.
p.setAge( p.getAge() + 1 );
person.put( "Lynn", p );
sess.commit();
activeTran = false;
}
finally
{
if ( activeTran ) sess.rollback();
}
The finally block in the snippet of
code ensures that a transaction is rolled back when an unexpected
exception occurs. It not only handles a LockDeadlockException exception,
but any other unexpected exception that might occur. The finally block handles the case where an exception occurs during a commit method invocation. This example is not the only
way to deal with unexpected exceptions, and there might be cases where
an application wants to catch some of the unexpected exceptions that
can occur and display one of its application exceptions. You can add
catch blocks as appropriate, but the application must ensure that
the snippet of code does not exit without completing the transaction.