Show warning when EL not found

Question

I'm creating a JSF Applikation and i would like to get some kind of warning (preferably i the console) if i make typos in my EL-Expression.

Example: On my page i wanted to show some Text that is localized. The locale-config in faces-config.xml is properly set up and works with the var 'msgs'.

I used this code on my page:

<h:outputText value="#{msg.title_edit_customer}"/>

When i checked my Page in the browser, nothing got showed. I took me a while to realize that i made a typo - with #{msgs.... it worked as expected.

Can i activate some kind of Debug-Output, so i can see directly that there is an invalid EL somewhere?

My Setup: Eclipse 4.4.2, Tomcat 8, MyFaces 2.2.8

Check if this helps... from what I remember it does...http://stackoverflow.com/questions/19193912/uses-of-javax-faces-project-stage — Kukeltje, Jul 02 '15 at 07:31
I have the PROJECT_STAGE already on Development, that dosen't help. — hinneLinks, Jul 02 '15 at 08:51
According to the https://tomcat.apache.org/tomcat-8.0-doc/RELEASE-NOTES.txt its EL 3.0 API. — hinneLinks, Jul 02 '15 at 09:26

score 0 · Accepted Answer · answered Jul 03 '15 at 05:43

Thanks to @SJuan76 i could figure it out:

Create your own javax.el.ELResolver, all the Methods can return null/false.
Open the Source of the Class org.apache.myfaces.el.unified.resolver.ScopedAttributeResolver and copy the methods facesContext(ELContext) and findScopedMap(FacesContext, Object) (since ScopedAttributeResolver is final, we can't extend it).

Edit the getValue-Method:

@Override
public Object getValue(ELContext context, Object base, Object property) {
    if(!context.isPropertyResolved()){
      //Douple Check false-positives
      boolean foundInScope = false;
      final Map<String, Object> scopedMap = findScopedMap(
            facesContext(context), property);
      if (scopedMap != null) {
        Object object = scopedMap.get(property);
        if (object != null) {
            foundInScope = true;
        }
      }
      if (!foundInScope) {
        log.warn(String.format("EL-Property %s couldn't be resolved",
                property));
    }
}
    return null;
}

Edit faces-config.xml to register your resolver:

<application> <el-resolver>com.myPackage.DebugELResolver</el-resolver> </application>
Since there are many Resolvers and each one does a little bit of the Resolving, our new Resolver should come last. Add following to web.xml:

<context-param> <param-name>org.apache.myfaces.EL_RESOLVER_COMPARATOR</param-name> <param-value>org.apache.myfaces.el.unified.CustomLastELResolverComparator</param-value> </context-param>
Now you'll get some log-Output, every time an expression couldn't be resolved:

03.07.2015 07:34:21 com.myPackage.DebugELResolver [http-nio-8080-exec-2] WARN EL-Property msgx couldn't be resolved

I couldn't figure out how to get the actual EL-Expression (e.g. #{msgx.title_edit_customer}.

Show warning when EL not found

1 Answers1