Null pointer exception for request scoped bean using AspectJ-style Spring AOP (@Around advising an @Transactional webservice method)

Question

I am using Spring 3.1.0.RC1. I have an Apache CXF based web service. I am trying to advise each @Transactional annotated service method.

I have an aspect with some Around advice. Inside the method I am squirreling away data into a request-scoped transaction payload bean. Later I ask for the uuid out of this payload in another singleton scoped bean. The result is a null pointer exception.

Caused by: java.lang.RuntimeException: java.lang.NullPointerException
    at com.spp.mui.jaxws.service.virtual._0_1.VirtualWebService.postOfferSet(VirtualWebService.java:209)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:309)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:80)
    at com.spp.mui.aop.tx.NewAgeTransactionLoggingAspect.logTransaction(NewAgeTransactionLoggingAspect.java:85)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:621)
    at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:610)
    at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:65)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:161)
    at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:80)
    at com.spp.mui.aop.ws.TraceWebServiceMethodAspect.invoke(TraceWebServiceMethodAspect.java:68)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:621)
    at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:610)
    at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:65)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:90)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202)
    at $Proxy95.postOfferSet(Unknown Source)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.apache.cxf.service.invoker.AbstractInvoker.performInvocation(AbstractInvoker.java:173)
    at org.apache.cxf.service.invoker.AbstractInvoker.invoke(AbstractInvoker.java:89)
    ... 49 more
Caused by: java.lang.NullPointerException
    at com.spp.mui.jaxws.agent.WSResponseAgent.getResponse(WSResponseAgent.java:28)
    at com.spp.mui.jaxws.agent.WSResponseAgent.getResponse(WSResponseAgent.java:18)
    at com.spp.mui.jaxws.handler.offer.PostVirtualOffersHandler.handle(PostVirtualOffersHandler.java:58)
    at com.spp.mui.jaxws.service.virtual._0_1.VirtualWebService.postOfferSet(VirtualWebService.java:205)
    ... 88 more

So what's going on in this stack trace?

A web service method (ie, postOfferSet) was invoked. That method was advised by an aspect with an @Around pointcut. That method is also @Transactional annotated.

UPDATE I have since updated the original configuration to be Java config based. With either an XML config or a Java config I run into the same problem. My Java config is the one currently in play, and the one I'd like help diagnosing. Please scroll down (skip ahead) to see this Java config below. (For others new to this post read on).

My aspect config looks a little like

 <aop:aspectj-autoproxy />

 <bean id="newAgeTxLoggingAspect" class="com.spp.mui.aop.tx.NewAgeTransactionLoggingAspect">
    <property name="transactionLogService" ref="txLogServiceEngine" />
    <property name="securable" ref="securityAgent" />
    <property name="loggableTransactionToken" ref="loggableTransactionToken" />
    <property name="logQuery" value="${newAgeTxLoggingAspect.logQuery}" />
    <property name="logReply" value="${newAgeTxLoggingAspect.logReply}" />
    <property name="logSubmit" value="${newAgeTxLoggingAspect.logSubmit}" />
    <property name="maxReplySize" value="${newAgeTxLoggingAspect.maxReplySize}" />
    <property name="maxRequestSize" value="${newAgeTxLoggingAspect.maxRequestSize}" />
    <property name="order" value="5" />
</bean>

As mentioned earlier the loggableTransactionToken is request-scoped.

Here's the bean def for it

<!-- 
    Request scoped bean that allows LoggableTransaction instances to be created and accessed on a single-thread of execution
    Consult http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/beans.html#beans-factory-scopes-other-injection 
-->
<bean id="loggableTransactionToken" class="com.spp.mui.commons.spring.LoggableTransactionToken" scope="request">
    <aop:scoped-proxy proxy-target-class="false"/>
</bean>

The aforementioned web service method delegates to a Handler

Here's a snippet from the Handler

 @Override
public ConfirmationType handle(OfferSetType request) {
    // step 1: convert from JAXB type to domain objects
    List<MktVirtualOffer> candidateOffers = codecService.convert(request, List.class);
    ...
    // step 4: get response -- response encapsulates transaction id
    return responder.getResponse();
}

Notice the Handler uses a Responder?

Here's a snippet from the Responder, aka WSResponseAgent

@Override
public ConfirmationType getResponse() {
    ConfirmationType response = new ConfirmationType();
    LoggableTransaction lt = token.getToken();
    response.setTransactionID(lt.getUuid());
    logger.debug(ReflectUtil.toString(lt));
    return response;
}

Hopefully, I've provided enough to help you help me sleuth why I'm getting the NPE?

UPDATE Here's the Java config and additional impl

AOP config

@Configuration
@EnableAspectJAutoProxy
@Import(value = { LoggingConfig.class, AuthConfig.class })
public class AopConfig {

@Resource
private Environment env;

@Resource
private LoggingConfig loggingConfig;

@Resource
private AuthConfig authConfig;

/* Consult
 *   static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/transaction.html#transaction-declarative-applying-more-than-just-tx-advice
 *   and http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/aop.html#aop-ataspectj-advice-ordering
 */

@Bean
public NewAgeTransactionLoggingAspect txLoggingAspect() {
    NewAgeTransactionLoggingAspect aspect = new NewAgeTransactionLoggingAspect();
    aspect.setEnvironment(env);
    aspect.setLoggableTransactionToken(loggingConfig.loggableTxToken());
    aspect.setSecurable(authConfig.securable());
    aspect.setTransactionLogService(loggingConfig.txLogService());
    aspect.setLogQuery(Boolean.valueOf(env.getProperty("newAgeTxLoggingAspect.logQuery", Boolean.toString(true))));
    aspect.setLogReply(Boolean.valueOf(env.getProperty("newAgeTxLoggingAspect.logReply", Boolean.toString(true))));
    aspect.setLogSubmit(Boolean.valueOf(env.getProperty("newAgeTxLoggingAspect.logSubmit", Boolean.toString(true))));
    aspect.setMaxRequestSize(Integer.valueOf(env.getProperty("newAgeTxLoggingAspect.maxRequestSize", "100000000")));
    aspect.setMaxReplySize(Integer.valueOf(env.getProperty("newAgeTxLoggingAspect.maxReplySize", "100000000")));
    aspect.setOrder(Integer.valueOf(env.getProperty("newAgeTxLoggingAspect.order", "5")));
    return aspect;
}


}

Here's a snippet from the config responsible for setting up the NewAgeTransactionLoggingService and the LoggableTransactionToken

@Bean
public TransactionLogService txLogService() {
    HibernateTransactionLogService service = new HibernateTransactionLogService();
    service.setLogParameters(Boolean.valueOf(Boolean.toString(true)));
    service.setTimeDispatcher(timeConfig.timeDispatcher());
    service.setSessionFactory(sessionFactory);
    return service;
}


/**
 * @return <p>Request scoped bean that allows LoggableTransaction instances to be created and accessed on a request.<br/>
 * Consult <a href="http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/beans.html#beans-factory-scopes-other-injection">Bean Factory Scopes</a></p>
 */
@Bean
@Scope(value="request", proxyMode=ScopedProxyMode.INTERFACES)
public Token<LoggableTransaction> loggableTxToken() {
    // XXX Is this is the correct way to specify a request-scoped bean?
    LoggableTransactionToken token = new LoggableTransactionToken();
    return token;
}

Here's the aspect's method with @Around advice.

@Around("com.spp.mui.aop.Advisables.transactionLoggable()")
public Object logTransaction(ProceedingJoinPoint pjp) throws Throwable {
    // Prepare to log the execution time of the method call..
    long t0 = 0;
    t0 = System.currentTimeMillis();

    Object resultObject = null;

    try {
        resultObject = pjp.proceed();
    } catch (Throwable t) {
        logFailedTransactionAndRethrow(pjp, t0, t);
    }

    logSuccessfulTransaction(pjp, t0, resultObject);

    return resultObject;
}

Answer 1

So, I had to solve this one myself again.

The basics:

1) Create a custom ServletFilter, create the LoggableTransaction and set on token there. I extended Spring's OncePerRequestFilter and used WebApplicationContextUtils to fetch request scoped bean within doFilterInternal method.

2) Register this Filter in web.xml. Also be sure to register Spring's RequestContextListener and ContextLoaderListener.

3) The aspect implementation above, remains the same, save for the pointcut reference. The pointcut now references a service method (one that the web service delegates to).

4) This was the most critical... if the token does NOT implement an interface, then the bean definition should be adorned with @Scope(value="request", proxyMode=ScopedProxyMode.TARGET_CLASS). You'll need CGLib on the classpath. I needed it anyway for Hibernate.

Things worked beautifully afterwards.