Unhandled async exception in Resource with Server-Sent Event RESTEasy + Spring Integracion - spring

Question

The Task: The API is built using JAX-RS RESTEasy and Spring(RESTEasy-Spring Dependency) in order to enable API to use Spring dependency injection features, and also . Here everything is working fine. Then, In a resource there is a method to send messages from a server to the client in real-time(Server-Sent Event). I took this code(enter link description here) to build the method, but in the example EJB is used and some concurrency annotation defined there(#Singleton, #LOCK, LockType.{READ,WRITE}).
The Problem: When I consume that method the server throw the following exception:
20:15:29,669 ERROR [org.jboss.resteasy.resteasy_jaxrs.i18n] (default task-1) RESTEASY002020: Unhandled asynchronous exception, sending back 500: org.jboss.resteasy.spi.UnhandledException: java.lang.NullPointerException
I guest the problem is related to concurrency. First, the application was standalone(RUNNING ON JETTY), then it was deployed on wildfly application server in order to use EJB features and replicate the same example. However, due to the fact I use RESTEasy + Spring the resource(JAX-RS Resource) has to be annotated with #Component and managed by Spring Container. I tried to replace that with EJB #Singleton annotation and use #Lock() annotation in the methods as well, but when that is done the resource is not found(not deploy). I guest it is required the resource to be annotated with #Component in order to get this integration(RESTEasy + Spring) working. I searched about concurrency with Java SE and made use of the following package java.util.concurrent.locks but with no success.
These are my interface and class:
package edu.cibertec.votoelectronico.resource;
import java.io.IOException;
import javax.ejb.Lock;
import javax.ejb.LockType;
import javax.ws.rs.DefaultValue;
import javax.ws.rs.GET;
import javax.ws.rs.HeaderParam;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.HttpHeaders;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import javax.ws.rs.sse.SseEventSink;
import org.springframework.context.event.EventListener;
import edu.cibertec.votoelectronico.application.event.EmitirVotoEvent;
#Path("/votoelectronico/subscribe")
public interface SSEVotoElectronicoResource {
#GET
#Lock(LockType.READ)
#Path("/resultado")
#Produces(MediaType.SERVER_SENT_EVENTS)
public void obtenerResultados(#HeaderParam(HttpHeaders.LAST_EVENT_ID_HEADER) #DefaultValue("-1") int lastEventId,
#Context SseEventSink eventSink) throws IOException;
#Lock(LockType.WRITE)
#EventListener
public void onEmitirVotoEvent(EmitirVotoEvent domainEvent);
#GET
#Path("/")
#Produces(MediaType.APPLICATION_JSON)
public Response test();
}
package edu.cibertec.votoelectronico.resource;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.function.Function;
import java.util.stream.Collectors;
import javax.annotation.PostConstruct;
//import javax.ejb.Lock;
//import javax.ejb.LockType;
//import javax.ejb.Singleton;
import javax.ws.rs.InternalServerErrorException;
import javax.ws.rs.Path;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.Response;
import javax.ws.rs.sse.OutboundSseEvent;
import javax.ws.rs.sse.Sse;
import javax.ws.rs.sse.SseBroadcaster;
import javax.ws.rs.sse.SseEventSink;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import edu.cibertec.votoelectronico.application.event.EmitirVotoEvent;
import edu.cibertec.votoelectronico.domain.complex.VotoResumen;
import edu.cibertec.votoelectronico.dto.VotoResumenDto;
import edu.cibertec.votoelectronico.mapping.MapperFactoryRegistry;
import edu.cibertec.votoelectronico.resource.communication.BaseResponse;
import edu.cibertec.votoelectronico.resource.communication.ResumenProcesoResponse;
import edu.cibertec.votoelectronico.service.VotoService;
//#Singleton
#Path("/votoelectronico/subscribe")
#Component
public class SimpleSSEVotoElectronicoResource implements SSEVotoElectronicoResource {
private final Logger LOG = LoggerFactory.getLogger(SimpleSSEVotoElectronicoResource.class);
private Sse sse;
private final Lock readLock;
private final Lock writeLock;
#Autowired
private VotoService service;
#Autowired
private MapperFactoryRegistry mapper;
private SseBroadcaster sseBroadcaster;
private int lastEventId;
private final List<ResumenProcesoResponse> messages = new ArrayList<ResumenProcesoResponse>();
public SimpleSSEVotoElectronicoResource() {
ReadWriteLock readWriteLock = new ReentrantReadWriteLock(true);
this.readLock = readWriteLock.readLock();
this.writeLock = readWriteLock.writeLock();
}
#PostConstruct
public void init() {
LOG.info("On Init method...");
}
#Context
public void setSse(Sse sse) {
this.sse = sse;
this.sseBroadcaster = this.sse.newBroadcaster();
this.sseBroadcaster.onError((o, e) -> {
LOG.error("Ocurred an error on broadcasting: ", e);
});
this.sseBroadcaster.onClose((eventSink) -> {
LOG.info("Broadcast closed: ", eventSink);
});
}
#Override
// #Lock(LockType.READ)
public void obtenerResultados(int lastEventId, SseEventSink eventSink) throws IOException {
readLock.lock();
try {
if (lastEventId >= 0)
this.replyLastMessage(lastEventId, eventSink);
sseBroadcaster.register(eventSink);
LOG.info("Client has being registered");
} finally {
readLock.unlock();
}
}
#Override
// #Lock(LockType.WRITE)
public void onEmitirVotoEvent(EmitirVotoEvent domainEvent) {
writeLock.lock();
try {
LOG.info("EmitirVoto Event received");
ResumenProcesoResponse response = this.fetchResumenProceso();
this.messages.add(response);
OutboundSseEvent event = createEvent(response, ++this.lastEventId);
LOG.info("Server about to send Event");
this.sseBroadcaster.broadcast(event);
} finally {
writeLock.unlock();
}
}
private void replyLastMessage(int lastEventId, SseEventSink eventSink) {
try {
for (int i = lastEventId; i < messages.size(); i++) {
eventSink.send(createEvent(messages.get(i), i + 1));
}
} catch (Exception e) {
throw new InternalServerErrorException("Could not reply messages ", e);
}
}
private ResumenProcesoResponse fetchResumenProceso() {
ResumenProcesoResponse response = null;
try {
LOG.info("Fetching proccess resume..");
Collection<VotoResumen> resultados = this.service.results();
Function<VotoResumen, VotoResumenDto> convert = (VotoResumen object) -> this.mapper.convertFrom(object,
VotoResumenDto.class);
Collection<VotoResumenDto> collection = resultados.stream().map(convert).collect(Collectors.toList());
response = new ResumenProcesoResponse(collection);
} catch (Exception e) {
LOG.error("Ocurred an error while trying to get resume. " + e.getMessage());
response = new ResumenProcesoResponse(e.getMessage());
}
return response;
}
private OutboundSseEvent createEvent(ResumenProcesoResponse response, int id) {
return this.sse.newEventBuilder().id(String.valueOf(id)).data(response).build();
}
#Override
public Response test() {
try {
return Response.status(Response.Status.OK).entity(new BaseResponse(true, "")).build();
} catch (Exception e) {
return Response.status(Response.Status.INTERNAL_SERVER_ERROR).entity(new BaseResponse(false, e.toString()))
.build();
}
}
}
Full error description:
20:15:29,669 ERROR [org.jboss.resteasy.resteasy_jaxrs.i18n] (default task-1) RESTEASY002020: Unhandled asynchronous exception, sending back 500: org.jboss.resteasy.spi.UnhandledException: java.lang.NullPointerException
at org.jboss.resteasy.core.ExceptionHandler.handleApplicationException(ExceptionHandler.java:82)
at org.jboss.resteasy.core.ExceptionHandler.handleException(ExceptionHandler.java:346)
at org.jboss.resteasy.core.SynchronousDispatcher.writeException(SynchronousDispatcher.java:193)
at org.jboss.resteasy.core.SynchronousDispatcher.asynchronousExceptionDelivery(SynchronousDispatcher.java:510)
at org.jboss.resteasy.core.AbstractAsynchronousResponse.internalResume(AbstractAsynchronousResponse.java:232)
at org.jboss.resteasy.plugins.server.servlet.Servlet3AsyncHttpRequest$Servlet3ExecutionContext$Servle3AsychronousResponse.resume(Servlet3AsyncHttpRequest.java:117)
at org.jboss.resteasy.core.ResourceMethodInvoker.invokeOnTargetAfterFilter(ResourceMethodInvoker.java:431)
at org.jboss.resteasy.core.ResourceMethodInvoker.lambda$invokeOnTarget$0(ResourceMethodInvoker.java:370)
at org.jboss.resteasy.core.interception.PreMatchContainerRequestContext.filter(PreMatchContainerRequestContext.java:356)
at org.jboss.resteasy.core.ResourceMethodInvoker.invokeOnTarget(ResourceMethodInvoker.java:372)
at org.jboss.resteasy.core.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:344)
at org.jboss.resteasy.core.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:317)
at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:440)
at org.jboss.resteasy.core.SynchronousDispatcher.lambda$invoke$4(SynchronousDispatcher.java:229)
at org.jboss.resteasy.core.SynchronousDispatcher.lambda$preprocess$0(SynchronousDispatcher.java:135)
at org.jboss.resteasy.core.interception.PreMatchContainerRequestContext.filter(PreMatchContainerRequestContext.java:356)
at org.jboss.resteasy.core.SynchronousDispatcher.preprocess(SynchronousDispatcher.java:138)
at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:215)
at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:227)
at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:56)
at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:51)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:590)
at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:74)
at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:129)
at io.opentracing.contrib.jaxrs2.server.SpanFinishingFilter.doFilter(SpanFinishingFilter.java:52)
at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:61)
at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131)
at io.undertow.servlet.handlers.FilterHandler.handleRequest(FilterHandler.java:84)
at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
at io.undertow.servlet.handlers.ServletChain$1.handleRequest(ServletChain.java:68)
at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
at org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.servlet.handlers.RedirectDirHandler.handleRequest(RedirectDirHandler.java:68)
at io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:132)
at io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46)
at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64)
at io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:60)
at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:77)
at io.undertow.security.handlers.NotificationReceiverHandler.handleRequest(NotificationReceiverHandler.java:50)
at io.undertow.security.handlers.AbstractSecurityContextAssociationHandler.handleRequest(AbstractSecurityContextAssociationHandler.java:43)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at org.wildfly.extension.undertow.deployment.GlobalRequestControllerHandler.handleRequest(GlobalRequestControllerHandler.java:68)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:269)
at io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:78)
at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:133)
at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:130)
at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48)
at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
at org.wildfly.extension.undertow.security.SecurityContextThreadSetupAction.lambda$create$0(SecurityContextThreadSetupAction.java:105)
at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1504)
at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1504)
at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1504)
at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1504)
at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1504)
at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:249)
at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:78)
at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:99)
at io.undertow.server.Connectors.executeRootHandler(Connectors.java:376)
at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:830)
at org.jboss.threads.ContextClassLoaderSavingRunnable.run(ContextClassLoaderSavingRunnable.java:35)
at org.jboss.threads.EnhancedQueueExecutor.safeRun(EnhancedQueueExecutor.java:1982)
at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.doRunTask(EnhancedQueueExecutor.java:1486)
at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1377)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NullPointerException
at edu.cibertec.votoelectronico.resource.SimpleSSEVotoElectronicoResource.obtenerResultados(SimpleSSEVotoElectronicoResource.java:90)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.jboss.resteasy.core.MethodInjectorImpl.invoke(MethodInjectorImpl.java:138)
at org.jboss.resteasy.core.ResourceMethodInvoker.internalInvokeOnTarget(ResourceMethodInvoker.java:517)
at org.jboss.resteasy.core.ResourceMethodInvoker.invokeOnTargetAfterFilter(ResourceMethodInvoker.java:406)
... 63 more
Example code:
package com.example.sse.boundary;
import com.example.sse.entity.DomainEvent;
import javax.annotation.PostConstruct;
import javax.ejb.Lock;
import javax.ejb.Singleton;
import javax.enterprise.event.Observes;
import javax.ws.rs.*;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.HttpHeaders;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.sse.OutboundSseEvent;
import javax.ws.rs.sse.Sse;
import javax.ws.rs.sse.SseBroadcaster;
import javax.ws.rs.sse.SseEventSink;
import java.util.ArrayList;
import java.util.List;
import static javax.ejb.LockType.READ;
import static javax.ejb.LockType.WRITE;
#Path("events-examples")
#Singleton
public class EventsResource {
#Context
Sse sse;
private SseBroadcaster sseBroadcaster;
private int lastEventId;
private List<String> messages = new ArrayList<>();
#PostConstruct
public void initSse() {
sseBroadcaster = sse.newBroadcaster();
sseBroadcaster.onError((o, e) -> {
// ...
});
}
#GET
#Lock(READ)
#Produces(MediaType.SERVER_SENT_EVENTS)
public void itemEvents(#HeaderParam(HttpHeaders.LAST_EVENT_ID_HEADER)
#DefaultValue("-1") int lastEventId,
#Context SseEventSink eventSink) {
if (lastEventId >= 0)
replayLastMessages(lastEventId, eventSink);
sseBroadcaster.register(eventSink);
}
private void replayLastMessages(int lastEventId, SseEventSink eventSink) {
try {
for (int i = lastEventId; i < messages.size(); i++) {
eventSink.send(createEvent(messages.get(i), i + 1));
}
} catch (Exception e) {
throw new InternalServerErrorException("Could not replay messages ", e);
}
}
private OutboundSseEvent createEvent(String message, int id) {
return sse.newEventBuilder().id(String.valueOf(id)).data(message).build();
}
#Lock(WRITE)
public void onEvent(#Observes DomainEvent domainEvent) {
String message = domainEvent.getContents();
messages.add(message);
OutboundSseEvent event = createEvent(message, ++lastEventId);
sseBroadcaster.broadcast(event);
}
}
The source code is here: enter link description here
I tried to catch the error but with no success.
Can you please help me out to solve this error or give some advices.