Getting NULL even-though messages are there in rabbitmq queue at consumer end

i have following code to read the messages in the specified queue at consumer end. Basically , i wan to read the message first in the queue and based on message content , do certain things to decide what to send in reply ... here is the code

public class RPCServer {

 public static void main(String[] args) throws IOException, TimeoutException, InterruptedException {
 SpringApplication.run(RPCServer.class, args);
 }


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


 private static final String RPC_QUEUE_NAME = "rpc_queue1";


 public RPCServer() throws IOException, TimeoutException {


 }


 @Bean
 public Queue queue() {
 return new Queue(RPC_QUEUE_NAME);
 }


 @Component
 public static class RpcListener {


 @RabbitListener(queues = RPC_QUEUE_NAME)
 public String reply() throws IOException, TimeoutException, ClassNotFoundException, SQLException {
 RabbitTemplate rabbitTemplate = null; 
 @SuppressWarnings("null")
 Object message = rabbitTemplate.receive(RPC_QUEUE_NAME);
 logger.info("Sent Message was: " + message);
                        // some processing 
                       return response;
      }
}
}

Not getting what is the issue in code. using spring AMQP core framework for all coding. getting NPE at following line:

Object message = rabbitTemplate.receive(RPC_QUEUE_NAME);

here is the stacktrace :

Caused by: java.lang.NullPointerException: null
        at com.infy.ci.unitdbamqpservice.RPCServer$RpcListener.reply(RPCServer.java:49) ~[classes!/:0.0.1-SNAPSHOT]
        at sun.reflect.GeneratedMethodAccessor28.invoke(Unknown Source) ~[na:na]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_151]
        at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_151]
        at org.springframework.messaging.handler.invocation.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:180) ~[spring-messaging-4.3.14.RELEASE.jar!/:4.3.14.RELEASE]
        at org.springframework.messaging.handler.invocation.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:112) ~[spring-messaging-4.3.14.RELEASE.jar!/:4.3.14.RELEASE]
        at org.springframework.amqp.rabbit.listener.adapter.HandlerAdapter.invoke(HandlerAdapter.java:49) ~[spring-rabbit-1.7.6.RELEASE.jar!/:na]
        at org.springframework.amqp.rabbit.listener.adapter.MessagingMessageListenerAdapter.invokeHandler(MessagingMessageListenerAdapter.java:126) ~[spring-rabbit-1.7.6.RELEASE.jar!/:na]
        ... 12 common frames omitted

further, as per the doc, if the queue does not have any messages , it returns null but i confirmed that, messages are there is queue and ready to consume. but still NPE please suggest

Regards,

Solution

RabbitTemplate rabbitTemplate = null; 
@SuppressWarnings("null")
Object message = rabbitTemplate.receive(RPC_QUEUE_NAME);

Of course you get an NPE, since the template is null!

Why do you have a template there at all?

I already explained in this answer that you need a parameter on your reply() method...

@RabbitListener(queues = RPC_QUEUE_NAME)
public String reply(String request) throws IOException, TimeoutException, ClassNotFoundException, SQLException {
    logger.info(request);
    return request.toUpperCase();
}

When there is no argument, the framework just calls your method with no data from the message.