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From <xiaochen.c...@barclays.com>
Subject NPE when a resource tries to use @Context injected ContextResolver
Date Sat, 20 Jul 2013 00:01:03 GMT
Hello,

I am using Curator's curator-x-discovery-sever and trying to set it up with Jersey and Tomcat.

I created my resource class, injected the class. Also injected those singletons mentioned.
(following this page http://curator.incubator.apache.org/curator-x-discovery-server/index.html
)

However, I am getting NPE when the contextResolver tries to getContext.

The ContextResolver singleton is injected, and it looks like the @Context injection isn't
happening.

Can someone please help me to see what is wrong with my code?

Thanks.

Here is my code, the highlighted line is where the exception happens:

Resource

@Path("compass")
public class CompassResource extends DiscoveryResource<ServicePayload>
{
    public CompassResource(@Context ContextResolver<DiscoveryContext<ServicePayload>>
resolver)
    {
        super(resolver.getContext(DiscoveryContext.class));
    }
}

Application

public class DiscoveryServerApplication extends Application
{
    @Override
    public Set<Class<?>> getClasses() {
        Set<Class<?>> s = new HashSet<Class<?>>();
        //s.add(MyResource.class);
        s.add(CompassResource.class);
        return s;
    }

    @Override
    public Set<Object> getSingletons() {
        final Set<Object> singletons = Sets.newHashSet();

        // inject ServiceDiscovery singleton
        CuratorFrameworkFactory.Builder builder = CuratorFrameworkFactory.builder()
                .connectString("localhost:2181").sessionTimeoutMs(300000).connectionTimeoutMs(30000)
                .retryPolicy(new ExponentialBackoffRetry(1000,3));
        CuratorFramework client = builder.build();
        client.start();

        ServiceDiscovery<ServicePayload> serviceDiscovery = ServiceDiscoveryBuilder.builder(ServicePayload.class)
                .client(client).basePath("/").build();
        singletons.add(serviceDiscovery);

        // inject DiscoveryContext singleton
        GenericDiscoveryContext<ServicePayload> discoveryContext = new GenericDiscoveryContext<ServicePayload>
                (serviceDiscovery, new RandomStrategy<ServicePayload>(), 500, ServicePayload.class);
        singletons.add(discoveryContext);

        // inject JsonServiceInstanceMarshaller singleton
        singletons.add(new JsonServiceInstanceMarshaller(discoveryContext));

        // inject JsonServiceInstancesMarshaller singleton
        singletons.add(new JsonServiceInstancesMarshaller(discoveryContext));

        // inject JsonServiceNamesMarshaller
        singletons.add(new JsonServiceNamesMarshaller());

        return singletons;
    }
}
web.xml

    <servlet>
        <servlet-name>Curator Discovery Server</servlet-name>
        <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
        <init-param>
            <param-name>javax.ws.rs.Application</param-name>
            <param-value>com.lb.eqr.discovery.server.DiscoveryServerApplication</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>Curator Discovery Server</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>

===========

Here is the exception:

root cause
java.lang.NullPointerException
        com.lb.eqr.discovery.server.CompassResource.<init>(CompassResource.java:23)
        sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
        sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
        java.lang.reflect.Constructor.newInstance(Constructor.java:513)
        org.glassfish.hk2.utilities.reflection.ReflectionHelper.makeMe(ReflectionHelper.java:1091)
        org.jvnet.hk2.internal.ClazzCreator.createMe(ClazzCreator.java:244)
        org.jvnet.hk2.internal.ClazzCreator.create(ClazzCreator.java:319)
        org.jvnet.hk2.internal.SystemDescriptor.create(SystemDescriptor.java:448)
        org.glassfish.jersey.process.internal.RequestScope.findOrCreate(RequestScope.java:157)
        org.jvnet.hk2.internal.Utilities.createService(Utilities.java:2203)
        org.jvnet.hk2.internal.ServiceLocatorImpl.getService(ServiceLocatorImpl.java:579)
        org.jvnet.hk2.internal.ServiceLocatorImpl.getService(ServiceLocatorImpl.java:566)
        org.glassfish.jersey.internal.inject.Injections.getOrCreate(Injections.java:172)
        org.glassfish.jersey.server.model.MethodHandler$ClassBasedMethodHandler.getInstance(MethodHandler.java:185)
        org.glassfish.jersey.server.internal.routing.PushMethodHandlerRouter.apply(PushMethodHandlerRouter.java:105)
        org.glassfish.jersey.server.internal.routing.RoutingStage._apply(RoutingStage.java:118)
        org.glassfish.jersey.server.internal.routing.RoutingStage._apply(RoutingStage.java:121)
        org.glassfish.jersey.server.internal.routing.RoutingStage._apply(RoutingStage.java:121)
        org.glassfish.jersey.server.internal.routing.RoutingStage._apply(RoutingStage.java:121)
        org.glassfish.jersey.server.internal.routing.RoutingStage._apply(RoutingStage.java:121)
        org.glassfish.jersey.server.internal.routing.RoutingStage.apply(RoutingStage.java:102)
        org.glassfish.jersey.server.internal.routing.RoutingStage.apply(RoutingStage.java:62)
        org.glassfish.jersey.process.internal.Stages.process(Stages.java:197)
        org.glassfish.jersey.server.ServerRuntime$1.run(ServerRuntime.java:215)
        org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
        org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
        org.glassfish.jersey.internal.Errors.process(Errors.java:315)
        org.glassfish.jersey.internal.Errors.process(Errors.java:297)
        org.glassfish.jersey.internal.Errors.process(Errors.java:267)
        org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:317)
        org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:198)
        org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:946)
        org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:323)
        org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:372)
        org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:335)
        org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:218)



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