Recipe8.2.Capturing the Value of the Field Being Accessed

Recipe 8.2. Capturing the Value of the Field Being Accessed

Problem

You want to capture the value of the field being accessed so that it can be used in your corresponding advice.

Solution

Use the after( ) returning(<ReturnValue>) form of advice with an identifier in the returning( ) part of the declaration to contain the value that has been accessed.

Discussion

Example 8-3 shows how the value of the MyClass.name attribute can be passed to the after( ) returning(<ReturnValue>) advice as triggered when the MyClass.name is accessed.

Example 8-3. Accessing the value of a field as it is returned when it is accessed

public aspect CaptureAccessedFieldValue  {    pointcut getNamePointcut( ) : get(String MyClass.name);    // Advice declaration    after( ) returning(String value) : getNamePointcut( )    {       System.out.println(          "-------------- Aspect Advice Logic ---------------");       System.out.println(          "In the advice picked by " + "getNamePointcut( )");       System.out.println(          "Signature: "             + thisJoinPoint.getStaticPart( ).getSignature( ));       System.out.println(          "Source Line: "             + thisJoinPoint.getStaticPart( ).getSourceLocation( ));              System.out.println("Value being accessed is " + value);              System.out.println(          "--------------------------------------------------");    } }