使用AspectJ监视Spring Boot应用程序中REST调用的运行时间

Question

I have a Spring Boot app with multiple classes that share a common HttpUtil class which makes Http requests. In the past, I have used AspectJ in the following:

@Around("execution(* com.gateway.TestGateway.getStatus(..))")
public Object GatewayStatus(ProceedingJoinPoint pjp) throws Throwable {
    StopWatch watch = new StopWatch();
    watch.start();
    Object output = pjp.proceed();
    watch.stop();
    log.error("Call took - [" + (watch.getTime()) + "]ms");
    return output;
}

This worked fine, I'd match the getStatus() method with the @Around annotation, but the gateway structure now has code surrounding the httputil call, and I only want to profile the rest call. The new gateway method looks like:

final HttpUtil httpUtil; //Constructor injected by Spring.

public ResponseEntity<String> getResponse(final String serviceUrl, final HttpEntity<String> httpEntity) throws Exception  {

    ResponseEntity<String> response = null;
    //Code here to verify the Entity
    try{
        response = httpUtil.postEntity(serviceUrl, httpEntity, String.class,
            httpUtil.getRestTemplate());
        //Logic here to work on the response.
    }
    catch(Exception e){
        log.error("Error occurred");
    }
    return response;
}

I realize I could re-factor this, or use the profiler on the HttpUtil class method itself, but how can I use AspectJ to match a snippet of code within an existing method? As in, run the when the postEntity() call begins and after the postEntity() call finishes but before the method returns.

I'm not too familiar with Pointcuts and other AspectJ properties. All I'm trying to do is log the execution time, but I want to learn more about AspectJ.

Answer 1

When you pick out a point in your program where you want to apply Advice and execute some extra code, like timing the postEntity() method call, you have to create join points and pointcut(s) for your chosen position. A pointcut defines what join points where your Advice will apply (where your timing code will start).

So, I think your question is specifically about how to define a pointcut at the call of postEntity() in the ClassThatHasGetResponse class.

Different ways to describe pointcuts are documented here and some nice pointcut examples are here .

For your question, you might have a pointcut like this:

cflow(execution(Object ClassThatHasGetResponse.com.package.getResponse(..))) && call(* HttpUtil.postEntity(..))

The above pointcut defines the spot where the control flow of execution is inside the method getResponse() of the class ClassThatHasGetResponse and a method call is made to postEntity() with any return type and any parameters.

You'll have to add this pointcut to @Around advice which captures the timing data, maybe like this:

@Around("cflow(execution(Object ClassThatHasGetResponse.com.package.getResponse(..))) && call(* HttpUtil.postEntity(..))")
public Object GatewayStatus(ProceedingJoinPoint pjp) throws Throwable {
    StopWatch watch = new StopWatch();
    watch.start();
    Object output = pjp.proceed();
    watch.stop();
    log.error("Call took - [" + (watch.getTime()) + "]ms");
    return output;
}

Since you're using Spring, it also may be worth noting that in Spring's support for AOP ( this is not the same as AspectJ, but it's easy to get confused about using one vs the other IMO, especially when first learning about AOP through Spring while using AspectJ ), a pointcut (composed of join points) is always a point of method execution, which simplifies a bit from the flexibility of AspectJ. Source