Spring AOP change value of methods argument on around advice

Question

Is it possible to change method argument value on basis of some check before executing using Spring AOP

My method

public String doSomething(final String someText, final boolean doTask) {
    // Some Content
    return "Some Text";
}

Advice method

public Object invoke(final MethodInvocation methodInvocation) throws Throwable {
    String methodName = methodInvocation.getMethod().getName();

    Object[] arguments = methodInvocation.getArguments();
    if (arguments.length >= 2) {
        if (arguments[0] instanceof String) {
            String content = (String) arguments[0];
            if(content.equalsIgnoreCase("A")) {
                // Set my second argument as false
            } else {
                // Set my second argument as true
            }
        }
    }
    return methodInvocation.proceed();
}

Please suggest me the way to set the method argument value as there is no setter options for the argument.

reto · Answer 1 · 2015-09-03T09:06:29.073

14

Yes that's possible. You need a ProceedingJoinPoint and instead of:

methodInvocation.proceed();

you can then call proceed with the new arguments, for example:

methodInvocation.proceed(new Object[] {content, false});

see http://docs.spring.io/spring-framework/docs/current/spring-framework-reference/html/aop.html#aop-ataspectj-advice-proceeding-with-the-call

edited Sep 03 '15 at 09:06

answered Sep 03 '15 at 07:52

reto

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4

Just be careful: these things are easily skipped during refactoring. If you don't have nice test suite it can hurt. – Rafal G. Sep 03 '15 at 08:52
Yes, absolutely! The arguments have to match and the refactoring tools are not going to help for such cases. – reto Sep 03 '15 at 08:53
But I used MethodInterceptor interface. What changes I have to make for ProceedingJoinPoint – Ashish Aggarwal Sep 03 '15 at 08:54
Did you try to change the interface to `ProceedingJoinPoint`? – reto Sep 03 '15 at 09:06

score 5 · Accepted Answer · answered Sep 03 '15 at 09:57

I got my answer using MethodInvocation

public Object invoke(final MethodInvocation methodInvocation) throws Throwable {
    String methodName = methodInvocation.getMethod().getName();

    Object[] arguments = methodInvocation.getArguments();
    if (arguments.length >= 2) {
        if (arguments[0] instanceof String) {
            String content = (String) arguments[0];
            if(content.equalsIgnoreCase("A")) {
                if (methodInvocation instanceof ReflectiveMethodInvocation) {
                    ReflectiveMethodInvocation invocation = (ReflectiveMethodInvocation) methodInvocation;
                    arguments[1] = false;
                    invocation.setArguments(arguments);
                }
            } else {
                if (methodInvocation instanceof ReflectiveMethodInvocation) {
                    ReflectiveMethodInvocation invocation = (ReflectiveMethodInvocation) methodInvocation;
                    arguments[1] = true;
                    invocation.setArguments(arguments);
                }
            }
        }
    }
    return methodInvocation.proceed();
}

score 5 · Answer 3 · answered Feb 02 '20 at 08:03

You can use Spring AOP, create point cut using @Around. Then you can use the below code to change the arguments of the method, based on the condition.

int index = 0;
Object[] modifiedArgs = proceedingJoinPoint.getArgs();

for (Object arg : proceedingJoinPoint.getArgs()) {
    if (arg instanceof User) {    // Check on what basis argument have to be modified.
        modifiedArgs[index]=user;
       }
    index++;
}
return proceedingJoinPoint.proceed(modifiedArgs);  //Continue with the method with modified arguments.

Spring AOP change value of methods argument on around advice

3 Answers3