Access process payload in ELResolver

[kaech]

Hi,

I would like to implement an ELResolver whose behavior depends on the process payload.
Is there a way to access the process variables from within an ELResolver like it is possible in a JavaDelegate?

Thanks in advance.

[frederikherema1]

You should extend the org.activiti.engine.impl.el.ExpressionManager and use your custom version on your ProcessEngineConfiguration (property "expressionManager").

You have some methods on there to create a new ELResolver to use in an execution. The variable-scope is passed in (= execution, task, …), which yiou can get variables from to do whatever magic you want in your EL-resolver.

protected ELResolver createElResolver(VariableScope variableScope) {
    CompositeELResolver elResolver = new CompositeELResolver();
    elResolver.add(new VariableScopeElResolver(variableScope));
    elResolver.add(new ArrayELResolver());
    elResolver.add(new ListELResolver());
    elResolver.add(new MapELResolver());
    elResolver.add(new DynamicBeanPropertyELResolver(ItemInstance.class, "getFieldValue", "setFieldValue")); //TODO: needs verification
    elResolver.add(new BeanELResolver());
  
    // CUSTOM MAGIC EL-RESOLVER
    elResolver.add(new MagicResolver(variableScrope));
    return elResolver;
  }

[kaech]

That works, thank you.

[casten2809]

Hello,

First: Thanks for this SourceCode.

But I've an other Problem now.

If I use a ServiceTask with an "activiti:expression=${exampleBean.exampleMethode(exampleVariable)" in my *.bpmn20.xml-file and use an own ExpressionManager with an own ELResolver to find my properties (the exambleVariable), my own ExpressionManager won't get the "Beans" from the ProcessEngineConfigurationImpl.

Is it possible to get the Beans, that where define in the ProcessEngineConfigurationImpl, to my own ExpressionManager?

Casten

[martin_grofcik]

Hi Casten,

answer is yes.
To answer how, I should understand your implementation. But you can access beans from process engine configuration.
(org.activiti.engine.impl.cfg.ProcessEngineConfigurationImpl#beans)

Refgards,
Martin

[casten2809]

Hi martin.grofcik,

thanks for your answer.

First I've tried your solution with the following statement:

<code>
<bean id="activiti.wop.processEngineConfiguration" class="org.activiti.spring.SpringProcessEngineConfiguration">
…
   <property name="beans">
       <map>
    <entry key="exampleBean" value-ref="exampleBean"></entry>
       </map>
   </property>
…
   <property name="expressionManager" ref="express"/>
…
</bean>

<bean name="express" class="de.example.bpmactiviti.impl.BpmExpressionManager">
   <constructor-arg name="beans" ref="beans"/>
</bean>

<bean name="beans" factory-bean="activiti.wop.processEngineConfiguration" factory-method="getBeans"/>
</code>

But this solution doesn't work. Have I interpret your solution wrong?
And what were the right solution.

I've find another solution:

<code>
<bean id="activiti.wop.processEngineConfiguration" class="org.activiti.spring.SpringProcessEngineConfiguration">
…  
   <property name="expressionManager">
      <bean class="de.example.bpmactiviti.impl.BpmExpressionManager">
         <constructor-arg name="beans">
            <map>
               <entry key="initializeControlExpert" value-ref="initializeControlExpert"></entry>
            </map>
         </constructor-arg>
      </bean>
    </property>
…
</bean>
</code>

But I think this isn't a nice solution.

[martin_grofcik]

Hi Casten,

From BpmExpressionManager point of view both solutions are the same. The difference is how beans are initialized and given to the BpmExpressionManager.
Did you get list of beans to BpmExpressionManager in the 1. solution (Why not?)

Regards
Martin

[casten2809]

Hi martin.grofcik,


No. I don't get some Beans for the BpmExpressionManager in the first solution.

As I have debbuged the source code I have seen, that as first the ExpressionManager will be set (org.activiti.spring.ProcessEngineFactoryBean) and after this the Beans are initialized (e.g. org.activiti.spring.SpringProcessEngineConfiguration).

I can't find out why this happened.


Regards

Casten