Myujth

My application structure is like

I created an annotation as below:-

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface SampleAnnotation 

Then created a Sample Interceptor:

public class SampleInterceptor implements MethodInterceptor 

 private static final Logger logger = LoggerFactory.getLogger(SampleInterceptor.class);

 @Inject
 SampleService sampleService; // this is not working

 public Object invoke(MethodInvocation invocation) throws Throwable 
 logger.info("SampleInterceptor : Interceptor Invoked");
 Object result = invocation.proceed();
 Observable<List<Sample>> observable = (Observable<List<Sample>>) result;
 SampleSender sender = null;
 List<Sample> sampleList = observable.toBlocking().first();

 for(Sample sample : sampleList ) 
 sender = new SampleSender();
 sender.setBoolean(sample.isBoolean());
 logger.info("Pushing Data into Sender");
 sampleService.insert(String.join("_", "key", "value"), sender); // here getting NullPointerException because sampleService is null
 
 return result;
 

Then I created a GuiceModule as below:-

public class SampleModule extends AbstractModule 
 @Override
 protected void configure() 
 bindInterceptor(Matchers.any(), Matchers.annotatedWith(SampleAnnotation.class), new SampleInterceptor());

Class in which I am using the above annotation is

// This class also have so many method and this was already declared and using in another services, I created a sample class here
class SampleClassForInterceptor 

 // this sampleMethod() is not a new method, its already created, 
 // now I am adding annotation to it, because after finishing this functionality, 
 // I want something should be done, so created annotation and added here
 @SampleAnnotation
 public Observable<List<Sample>> sampleMethod() 
 Sample sample = new Device();
 sample.setName("*** 7777");
 sample.setBoolean(true);
 List<Sample> list = new ArrayList<>();
 list.add(sample);
 Observable<List<Device>> observable = Observable.just(list);
 return observable;
 

I have a RestModule using which I am binding SampleClassForInterceptor as follows

public final class RestModule extends JerseyServletModule 
 // other classes binding
 bind(SampleClassForInterceptor.class).in(Scopes.SINGLETON);
 // other classes binding
 install(new SampleModule());

Now I have a bootsrap class in which I am binding RestModule

public class Bootstrap extends ServerBootstrap 
 binder.install(new RestModule());

Usage:-

@Path("service/sample")
public class SampleRS 
 @Inject
 SampleClassForInterceptor sampleClassForInterceptor;

 public void someMethod() 
 sampleClassForInterceptor.sampleMethod();
 

My interceptor functionality is started executing before executing sampleMethod() of SampleClassForInterceptor class, then after executing the sampleMethod() again coming back to Interceptor, now here I have a code snippet which will insert the result(which we got from sampleMethod()). This is where I am getting NullPointerException, I checked code and found that SampleService object not getting injected and its value is null

Note: I am using Microservices with RESTFUL services concept

when I used requestInjection in the SampleModule, then SampleService got injected inside interceptor i.e I modified the SampleModule code as follows

public class SampleModule extends AbstractModule 
 @Override
 protected void configure() 
 SampleInterceptor interceptor = new SampleInterceptor();
 requestInjection(interceptor);
 bindInterceptor(Matchers.any(), Matchers.annotatedWith(SampleAnnotation.class), interceptor);