LinkageError / NoSuchMethodError when using with JSF2

[iravanchi]

Hi,

I'm setting up my Activiti app with Tomcat, Spring, and JSF 2 (MyFaces) Frontend.
The problem is clashing EL library used by Activiti (JUEL) with the EL specification used by Tomcat and MyFaces.

By default, I get a LinkageError for ELResolver interface when starting the MyFaces listener in Tomcat.
First, I thought it is because there are two ELResolver definitions in the classpath (one in juel, and one in Tomcat's el-api.jar).
So I replaced el-api in tomcat\lib with juel. No luck!

I even searched every JAR file in the JDK, Tomcat, and my WEB-INF\lib, and the only ELResolver present was juel's. But I still get that LinkageError.

Anyway,… I thought the better way to do so is to remove the redundant EL API. So, I added an "exclusion" in the my pom.xml (maven) to omit JUEL jar file as the dependency, and added juel-impl myself (only having the EL implementation, not the API). So that I can use Tomcat without any change outside my webapp. This time, I get a NoSuchMethorError, in the constructor of ProcessEngineFactoryBean (javax.el.ExpressionFactory.newInstance()).
The method is not present in the Tomcat's included EL-API, and I guess it is a change in the JSR Spec that is included in JUEL but not in the EL-API.

So, right now I'm stuck. This was as far as I could go. The alternate option for me is to change the Activiti source code.
Any recommendations?

Here are the exception traces:

Originally, or when replacing the el-api.jar with juel.jar:
java.lang.LinkageError: loader constraint violation: when resolving interface method "javax.servlet.jsp.JspApplicationContext.addELResolver(Ljavax/el/ELResolverV" the class loader (instance of org/apache/catalina/loader/WebappClassLoader) of the current class, org/apache/myfaces/webapp/Jsp21FacesInitializer, and the class loader (instance of org/apache/catalina/loader/StandardClassLoader) for resolved class, javax/servlet/jsp/JspApplicationContext, have different Class objects for the type javax/el/ELResolver used in the signature
   at org.apache.myfaces.webapp.Jsp21FacesInitializer.configureResolverForJSP(Jsp21FacesInitializer.java:123)
   at org.apache.myfaces.webapp.Jsp21FacesInitializer.initContainerIntegration(Jsp21FacesInitializer.java:77)
   at org.apache.myfaces.webapp.AbstractFacesInitializer.initFaces(AbstractFacesInitializer.java:113)
   at org.apache.myfaces.webapp.StartupServletContextListener.initFaces(StartupServletContextListener.java:186)
   at org.apache.myfaces.webapp.StartupServletContextListener.contextInitialized(StartupServletContextListener.java:159)
   at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4135)
   at org.apache.catalina.core.StandardContext.start(StandardContext.java:4630)


When using juel-impl:
Caused by: java.lang.NoSuchMethodError: javax.el.ExpressionFactory.newInstance()Ljavax/el/ExpressionFactory;
   at org.activiti.engine.impl.el.ExpressionManager.<init>(ExpressionManager.java:55)
   at org.activiti.engine.impl.cfg.ProcessEngineConfiguration.<init>(ProcessEngineConfiguration.java:164)
   at org.activiti.engine.impl.cfg.spring.ProcessEngineFactoryBean.<init>(ProcessEngineFactoryBean.java:51)
   at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
   at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
   at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
   at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
   at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:100)
   … 52 more

Thanks,
-Hamed

[iravanchi]

Well, I found a way:
I needed to remove JUEL from my WEB-INF\lib when I added it to tomcat's lib folder. It works now.
But a solution for this issue that doesn't involve changing the Tomcat's lib folder (anything outside the context root) would be nice.
I believe there's an issue registered for it in Activiti's JIRA.

[jbarrez]

It's a known issue at the moment, and we are working on it to resolve it.

The workaround is indeed as you describe: remove the juel libs from the Tomcat lib, which removes the clashes with the EL resolver of Tomcat (which is a different version of EL)