Java Play Mustache NPE Error

Question

We are getting a mustache play error in production (amazon linux EC2 AMI) but not in development (MACs) and we have tried upgrading the jvm, using the jdk instead, and changing from a tomcat deploy model to match our development environments as much as possible but nothing is working. Please any help would be greatly appreciated. We have lots of shared code in java and javascript using mustache and it would be a big deal to rewrite everything if we had to ditch mustache on the java side.

20:48:52,403 ERROR ~

@6al2dd0po
Internal Server Error (500) for request GET /mystuff/people

Execution exception (In {module:mustache-0.2}/app/play/modules/mustache/MustacheTags.java around line 32)
NullPointerException occured : null

play.exceptions.JavaExecutionException
    at play.templates.BaseTemplate.throwException(BaseTemplate.java:90)
    at play.templates.GroovyTemplate.internalRender(GroovyTemplate.java:257)
    at play.templates.Template.render(Template.java:26)
    at play.templates.GroovyTemplate.render(GroovyTemplate.java:187)
    at play.mvc.results.RenderTemplate.<init>(RenderTemplate.java:24)
    at play.mvc.Controller.renderTemplate(Controller.java:660)
    at play.mvc.Controller.renderTemplate(Controller.java:640)
    at play.mvc.Controller.render(Controller.java:695)
    at controllers.MyStuff.people(MyStuff.java:183)
    at play.mvc.ActionInvoker.invokeWithContinuation(ActionInvoker.java:548)
    at play.mvc.ActionInvoker.invoke(ActionInvoker.java:502)
    at play.mvc.ActionInvoker.invokeControllerMethod(ActionInvoker.java:478)
    at play.mvc.ActionInvoker.invokeControllerMethod(ActionInvoker.java:473)
    at play.mvc.ActionInvoker.invoke(ActionInvoker.java:161)
    at Invocation.HTTP Request(Play!)
Caused by: java.lang.NullPointerException
    at play.modules.mustache.MustacheTags._template(MustacheTags.java:32)
    at play.modules.mustache.MustacheTags$_template.call(Unknown Source)
    at /app/views/User/people.html.(line:22)
    at play.templates.GroovyTemplate.internalRender(GroovyTemplate.java:232)
    ... 13 more

Answer 1

Seems the issue is with the threadlocal. In Prod as per my logs, the session gets initialized with the main thread.

     [2012-06-30 18:35:38,102] INFO 10097[**main**] - Mustache module initialized

However, MustacheTag tries to access with various thread like this during request.

     [2012-06-30 17:48:44,669] INFO 66048[**play-thread-1**] - [{module:mustache-0.2}/app/play/modules/mustache/MustacheTags.java:46] _meta() :: MustachePlugin.session():null

So I changed the implementation of MustachePlugin like this.Changed line commented out:

    //private static ThreadLocal<MustacheSession> session_ = new ThreadLocal<MustacheSession>();
    private static MustacheSession _session = null;
    public static MustacheSession session(){
    //return session_.get();
    return _session;
    }
    public void onConfigurationRead(){
    // some code
    _session = new MustacheSession(compiler, root);
    // some code
    }

And it is working fine now in prod mode! I see no reason why it should have been in a ThreadLocal in the first place as the session gets initialized at startup!