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ilog.rules.engine
Interface IlrExceptionHandler

All Superinterfaces:

Serializable

public interface IlrExceptionHandler
extends Serializable

An exception handler manages the way an execution context processes the exceptions thrown during the execution of rules. Only instances of IlrUserRuntimeException are subject to processing by an exception handler. Those exceptions are thrown by the user's code executed from the rule engine, such as constructors, methods, field accesses, and so on.

At its creation, a context does not have any exception handler. When an exception is thrown in the user's code, the rule engine catches it and an instance of IlrUserRuntimeException is constructed with the former exception as its target, then the IlrUserRuntimeException is thrown.

When an exception handler has been set for an execution context, the constructed IlrUserRuntimeException is not thrown. Instead, it is processed by the exception handler.

If the exception occurs during the evaluation of rule condition, then the result of the processing is the result of the evaluation. For example, if the processing returns false, then the tests are considered as false. If the exception occurs within an action, then the result of the processing is ignored. The remainder of the action part of the rule which caused the exception is never executed. If its occurs within a ruleflow, then the result of the processing is ignored. The remainder of the ruleflow is not executed.

It is possible to differentiate the way exceptions are processed according to their origin (condition or action part). In particular, the processing can choose to throw the exception itself or another exception.

The following example considers the tests as false if their evaluation throws exceptions, but does not process exceptions in the action part of rules:

   context.setExceptionHandler(new IlrExceptionHandler() {
     public boolean handleException(IlrUserRuntimeException ex)
     {
       if (ex.isInConditions()) return false;
       else throw ex;
     }
   });
 

Note: As IlrContext is serializable, an exception handler is also serializable. It is the user's responsibility to ensure that the exception handler object supports Java serialization.

Method Summary

boolean

handleException(IlrUserRuntimeException ex) Processes an exception and returns a Boolean value as a result.

Method Detail

handleException

boolean handleException(IlrUserRuntimeException ex)

Processes an exception and returns a Boolean value as a result. The value is used as the test evaluation if the exception has occurred in a rule condition part. Otherwise, it is ignored.

Parameters:

ex - An IlrUserRuntimeException.

Returns:

a Boolean value, result of the processing.