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copied!<p>In my project (I think I'll have to write about it on my blog <a href="http://toomuchcoding.blogspot.com" rel="nofollow">http://toomuchcoding.blogspot.com</a> where I have some articles about Drools) I wrote a custom Listener in the following manner (I think I found a nice tutorial over here <a href="http://members.inode.at/w.laun/drools/CustomConsequenceExceptionHandlingHowTo.html" rel="nofollow">http://members.inode.at/w.laun/drools/CustomConsequenceExceptionHandlingHowTo.html</a>)</p> <p>I defined my KnowledgeBase as a bean in my applicationContext:</p> <pre><code><drools:kbase id="fxKBase"> <drools:resources> <drools:resource type="DRL" source="classpath:path/first.drl"/> <drools:resource type="DRL" source="classpath:path/second.drl"/> </drools:resources> <drools:configuration> <drools:consequenceExceptionHandler handler="a.b.c.MyConsequenceExceptionHandler" /> </drools:configuration> </drools:kbase> </code></pre> <p>Then I defined MyConsequenceExceptionHandler</p> <pre><code>public class MyConsequenceExceptionHandler implements ConsequenceExceptionHandler { @Override public void handleException(Activation activation, WorkingMemory workingMemory, Exception exception) { throw new MyConsequenceException(activation, workingMemory, exception); } </code></pre> <p>and the MyConsequenceException:</p> <pre><code>public class MyConsequenceException extends RuntimeException { private final WorkingMemory workingMemory; private final Activation activation; public MyConsequenceException(final Activation activation, final WorkingMemory workingMemory, final Exception exception) { super(exception); this.activation = activation; this.workingMemory = workingMemory; } @Override public String getMessage() { StringBuilder sb = new StringBuilder( "Exception executing consequence for " ); if( activation != null && ( activation.getRule() ) != null ){ Rule rule = activation.getRule(); String ruleName = rule.getName(); sb.append("rule [\"").append( ruleName ).append( "\"]. " ); } else { sb.append( "rule, name unknown" ); } Throwable throwable = ExceptionUtils.getRootCause(getCause()); sb.append("The thrown exception is [").append(throwable).append("]. "); return sb.toString(); } @Override public String toString() { return getMessage(); } </code></pre> <p>}</p> <p>In that way when an exception is thrown you will get a custom message of your choosing. </p>

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