Question

I’m trying to use the expression #[process:processName:valueToProcess] in my flow.

This is my flow config:

<flow name="exampleFlow">
  <quartz:inbound-endpoint jobName="job1" cronExpression="0/5 * * * * ?" connector-ref="quartzConnector">
    <quartz:event-generator-job>
      <quartz:payload>foo</quartz:payload>
    </quartz:event-generator-job>
  </quartz:inbound-endpoint>

  <logger message="#[process:test:#[payload]]" level="INFO"/>
</flow>

<sub-flow name="test" doc:name="test">
  <component class="com.myComp.ComponentTest" doc:name="Java"/>
</sub-flow>

And this is my Java Component:

package com.myComp;

public class ComponentTest
{
  public String test(String s)
  {
    return s + "bar";
  }
}

The problem comes when the expression #[process:test:#[payload]] is evaluated. It throws this exception:

java.lang.NullPointerException
    at org.mule.component.AbstractComponent.invokeInternal(AbstractComponent.java:112)
    at org.mule.component.AbstractComponent.process(AbstractComponent.java:156)
    at org.mule.processor.chain.DefaultMessageProcessorChain.doProcess(DefaultMessageProcessorChain.java:99)
    at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:66)
    at org.mule.processor.chain.InterceptingChainLifecycleWrapper.doProcess(InterceptingChainLifecycleWrapper.java:56)
    at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:66)
    at org.mule.processor.chain.InterceptingChainLifecycleWrapper.process(InterceptingChainLifecycleWrapper.java:87)
    at org.mule.api.processor.MessageProcessors$LifecyleAwareMessageProcessorWrapper.process(MessageProcessors.java:114)
    at org.mule.expression.MessageProcessorExpressionEvaluator.evaluate(MessageProcessorExpressionEvaluator.java:87)
    at org.mule.expression.DefaultExpressionManager.evaluate(DefaultExpressionManager.java:273)
    at org.mule.expression.DefaultExpressionManager.evaluate(DefaultExpressionManager.java:209)
    at org.mule.expression.DefaultExpressionManager$1.match(DefaultExpressionManager.java:399)
    at org.mule.util.TemplateParser.parse(TemplateParser.java:156)
    at org.mule.util.TemplateParser.parse(TemplateParser.java:133)
    at org.mule.expression.DefaultExpressionManager.parse(DefaultExpressionManager.java:395)
    at org.mule.expression.DefaultExpressionManager.parse(DefaultExpressionManager.java:379)
    at org.mule.api.processor.LoggerMessageProcessor.log(LoggerMessageProcessor.java:89)
    at org.mule.api.processor.LoggerMessageProcessor.process(LoggerMessageProcessor.java:71)
    at org.mule.processor.chain.DefaultMessageProcessorChain.doProcess(DefaultMessageProcessorChain.java:99)
    at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:66)
    at org.mule.processor.AbstractInterceptingMessageProcessorBase.processNext(AbstractInterceptingMessageProcessorBase.java:105)
    at org.mule.interceptor.AbstractEnvelopeInterceptor.process(AbstractEnvelopeInterceptor.java:55)
    at org.mule.processor.AsyncInterceptingMessageProcessor.processNextTimed(AsyncInterceptingMessageProcessor.java:111)
    at org.mule.processor.AsyncInterceptingMessageProcessor$AsyncMessageProcessorWorker.doRun(AsyncInterceptingMessageProcessor.java:158)
    at org.mule.work.AbstractMuleEventWork.run(AbstractMuleEventWork.java:43)
    at org.mule.work.WorkerContext.run(WorkerContext.java:310)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

The same happens with any other scripting component.
I’m guessing it has something to do with my component lifecycle, but I couldn’t find a way to make it work.
If I replace my component with any other Mule processor (e.g. logger, stringAppend) it works fine.

Any help will be appreciated!

Answer 1

You’re right when you say it’s an initialization issue: for any reason, components in a sub-flow are not initialized the same way they are in a flow, ie. this works:

<flow name="test" doc:name="test">
  <component class="com.myComp.ComponentTest" doc:name="Java"/>
</flow>

I believe this is a bug hence I reported it. Please upvote the issue.

To make this work with an asynchronous event, like the ones the Quartz inbound endpoint generates, you will need to add processingStrategy="synchronous" to the called flow in order to invoke in synchronously, otherwise by default it will be invoke asynchronously (even if process:test:#[payload] expects a synchronous response). That’s a known quirk in Mule 3.

So the end solution is:

<flow name="test" processingStrategy="synchronous" doc:name="test">
  <component class="com.myComp.ComponentTest" doc:name="Java"/>
</flow>