Play & Deadbolt error

I get the following stack trace (bont not on the loaded page!) whenever I set any of my methods with the

@SubjectRequired or @SubjectNotRequired annotations:

play.api.http.HttpErrorHandlerExceptions$$anon$1: Execution exception[[CompletionException: java.lang.NullPointerException]]
    at play.api.http.HttpErrorHandlerExceptions$.throwableToUsefulException(HttpErrorHandler.scala:293)
    at play.api.http.DefaultHttpErrorHandler.onServerError(HttpErrorHandler.scala:220)
    at play.api.GlobalSettings$class.onError(GlobalSettings.scala:160)
    at play.api.DefaultGlobal$.onError(GlobalSettings.scala:188)
    at play.api.http.GlobalSettingsHttpErrorHandler.onServerError(HttpErrorHandler.scala:100)
    at play.core.server.netty.PlayRequestHandler$$anonfun$2$$anonfun$apply$1.applyOrElse(PlayRequestHandler.scala:100)
    at play.core.server.netty.PlayRequestHandler$$anonfun$2$$anonfun$apply$1.applyOrElse(PlayRequestHandler.scala:99)
    at scala.concurrent.Future$$anonfun$recoverWith$1.apply(Future.scala:344)
    at scala.concurrent.Future$$anonfun$recoverWith$1.apply(Future.scala:343)
    at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32)
Caused by: java.util.concurrent.CompletionException: java.lang.NullPointerException
    at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:273)
    at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:280)
    at java.util.concurrent.CompletableFuture.uniCompose(CompletableFuture.java:961)
    at java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:926)
    at java.util.concurrent.CompletableFuture$Completion.run(CompletableFuture.java:442)
    at play.core.j.HttpExecutionContext$$anon$2.run(HttpExecutionContext.scala:56)
    at play.core.j.HttpExecutionContext$$anon$2.run(HttpExecutionContext.scala:56)
    at akka.dispatch.TaskInvocation.run(AbstractDispatcher.scala:39)
    at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:415)
    at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
Caused by: java.lang.NullPointerException: null
    at be.objectify.deadbolt.java.cache.DefaultSubjectCache.apply(DefaultSubjectCache.java:80)
    at be.objectify.deadbolt.java.cache.DefaultSubjectCache.apply(DefaultSubjectCache.java:38)
    at be.objectify.deadbolt.java.ConstraintLogic.getSubject(ConstraintLogic.java:348)
    at be.objectify.deadbolt.java.ConstraintLogic.subjectTest(ConstraintLogic.java:116)
    at be.objectify.deadbolt.java.ConstraintLogic.subjectPresent(ConstraintLogic.java:72)
    at be.objectify.deadbolt.java.actions.SubjectPresentAction.lambda$testSubject$129(SubjectPresentAction.java:91)
    at java.util.Optional.orElseGet(Optional.java:267)
    at be.objectify.deadbolt.java.actions.AbstractSubjectAction.lambda$execute$118(AbstractSubjectAction.java:76)
    at java.util.concurrent.CompletableFuture.uniCompose(CompletableFuture.java:952)
    at java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:926)

My code looks like this:

In class implementing DeadboltHandler

@Override
public CompletionStage<Optional<? extends Subject>> getSubject(Context elContext) {
    return CompletableFuture.supplyAsync(
        () -> {
            try {
                return Optional.ofNullable(da.getUser(Integer.parseInt( elContext.session().get("userId"))));
            } catch (Exception e) {
                e.printStackTrace();
                return null;
            } 
        });
}

where is has a constructor:

DataAccess da;

DeadboltSecureHandler(Database db){
    da = new DataAccess(db);
}

And in class implementing HandlerCache

@Inject 
public DeadboltHandlerCache(Database db){
    DeadboltHandler defaultHandler = new DeadboltSecureHandler(db);
    handlers.put(HandlerKeys.DEFAULT.key, defaultHandler);
}

@Override
public DeadboltHandler apply(final String key){
    return handlers.get(key);
}

@Override
public DeadboltHandler get(){
    return defaultHandler;
}

Any ideas what I've messed up?

Solution

A few things...

The deadboltHandler you're using is null, and the most likely explanation for this is HandlerKeys.DEFAULT.key is not the same as be.objectify.deadbolt.java.ConfigKeys.DEFAULT_HANDLER_KEY.

If you check the documentation, you'll find the following bit (which leads me to guess you're using a version of Deadbolt older than 2.5.3):

Note the use of ConfigKeys.DEFAULT_HANDLER_KEY - this is the default handler key specified by all annotations. In previous versions of Deadbolt, annotation-driven constraints would use HandlerCache#apply(DEFAULT_HANDLER_KEY) to obtain the handler and so the default handler had to be associated with DEFAULT_HANDLER_KEY. As of Deadbolt 2.5.3, this has been improved and any annotation-driven constraint using the default handler key will instead use HandlerCache#get.

The next issue you're going to hit with your current code is:

When you return null, you're breaking the contract of the getSubject method. Whenever something returns CompletionStage<Optional<? extends Subject>>, the CompletionStage must contain an Optional. Instead of returning null, return Optional.empty().