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From Jordan Zimmerman <jor...@jordanzimmerman.com>
Subject Re: NPE when a resource tries to use @Context injected ContextResolver
Date Sat, 20 Jul 2013 21:26:57 GMT
BTW - how many thousands of man years have been lost to erasure?!! What a horrible mistake
that decision was.

-JZ

On Jul 20, 2013, at 2:24 PM, Jordan Zimmerman <jordan@jordanzimmerman.com> wrote:

> OK - I have a workaround. You need to create a wrapper class that acts as the context
resolver:
> 
> @Provider
> public class MyResolver implements ContextResolver<DiscoveryContext<ServicePayload>>
> {
>     private final GenericDiscoveryContext<ServicePayload> context;
> 
>     public MyResolver(GenericDiscoveryContext<ServicePayload> context)
>     {
>         this.context = context;
>     }
> 
>     @Override
>     public DiscoveryContext<ServicePayload> getContext(Class<?> type)
>     {
>         return context;
>     }
> }
> 
> In the Singletons, instead of adding discoveryContext, add:
> 
> 	new MyResolver(discoveryContext)
> 
> In my tests, this fixed the problem.
> 
> -Jordan
> 
> On Jul 19, 2013, at 5:01 PM, xiaochen.chen@barclays.com wrote:
> 
>> 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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>> 
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>> 
>> _______________________________________________
>> 
> 


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