Recipe8.4.Capturing the Value of a Field When It Is Modified

Recipe 8.4. Capturing the Value of a Field When It Is Modified

Problem

You want to capture the value of the field after it has been modified so it can be used in your corresponding advice.

Solution

Combine the args([Types | Identifiers]) pointcut with the set(Signature) pointcut to expose the new value of the field being set as an identifier on your pointcut that can be passed to the corresponding advice.

Discussion

Example 8-5 shows how the new value, that the MyClass.name attribute is being set to, can be passed to the before( ) advice.

Example 8-5. Accessing the new value of the field being set

public aspect CaptureModifiedFieldValue  {    pointcut setNamePointcut(String newValue) : set(String MyClass.name)                               && args(newValue);       // Advice declaration    before(String newValue) : setNamePointcut(newValue)    {       System.out.println(          "------------------- Aspect Advice Logic --------------------");       System.out.println(          "In the advice picked by " + "setNamePointcut( )");       System.out.println(          "Signature: "             + thisJoinPoint.getStaticPart( ).getSignature( ));       System.out.println(          "Source Line: "             + thisJoinPoint.getStaticPart( ).getSourceLocation( ));              System.out.println("Field Value set to: " + newValue);              System.out.println(          "------------------------------------------------------------");    } }