Question

请在多线程场景中提供帮助，但我很少在下面的代码中获得NullPointerException

public class CassPerfInterceptor {
    private static final Logger log = LoggerFactory
            .getLogger(CassPerfInterceptor.class);
   private Performance performance;
   @Autowired
   private QueueServerMbean queueServerMbean;
   @Around("target(org.springframework.data.repository.CrudRepository) || execution(public * com.owmessaging.*.dao.*.*Dao.*(..))")

   public Object invoke(ProceedingJoinPoint joinPoint) throws Throwable {

       long start = System.currentTimeMillis();
       try {
           Object obj =  joinPoint.proceed();

            performance = StatsProvider.getCassandraStats(joinPoint.getSignature().getName());
            if(performance != null){
              // Here I am getting NPE line number 30
                performance.add(System.currentTimeMillis()-start, false); 
            }
            return obj;
       }catch(DriverException de){
           queueServerMbean.sendNotification("CRITICAL", "DB Connectivity Error: "+de.getMessage());
           throw de;
       }
       catch(Exception e){
           log.error("Error: ",e);
           performance = StatsProvider.getCassandraStats(joinPoint.getSignature().getName());
           if(performance != null){
               performance.add(System.currentTimeMillis()-start, true); 
           }
           throw e;
   }
}
}

下面是堆栈跟踪：

11126 2016-07-04 17:16:58,448[http-nio-8014-exec-16]ERROR CassPerfInterceptor -Error:
 11127 
java.lang.NullPointerException
 11128         at com.owmessaging.qserv.stats.CassPerfInterceptor.invoke(CassPerfInterceptor.java:31)
 11129         at sun.reflect.GeneratedMethodAccessor39.invoke(Unknown Source)
 11130         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
 11131         at java.lang.reflect.Method.invoke(Method.java:497)
 11132         at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:621)
 11133         at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:610)
 11134         at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:68)
 11135         at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:168)
 11136         at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
 11137         at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
 11138         at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:208)
 11139         at com.sun.proxy.$Proxy79.insertMsgInfo(Unknown Source)
 11140         at com.owmessaging.qserv.service.impl.QueueServiceImpl.enqueue(QueueServiceImpl.java:151)

即使我应用预防性检查if (performance != null)，我仍然会获得NPE。上面检查没有线程安全。（但请注意，这是非常罕见的情况，我得到了7000个请求中的NPE。）

即使在进行预防性检查后仍然存在NullpointerException

0 个答案: