aspectj 以get和set切入点的形式提供了类属性上的任何访问和修改的监视。

捕获何时访问对象的属性

get(FieldPattern)
Picks out each field reference join point whose signature matches FieldPattern. [Note that references to constant fields (static final fields bound to a constant string object or primitive value) are not join points, since Java requires them to be inlined.]

说明
get切入点触发直接在其中，而不是访问器方法的调用上
不能捕获对静态属性的访问,也不适合常量

get捕获何时访问对象的属性

捕获访问的字段值

after( Formals ) returning [ ( Formal ) ]

捕获何时修改对象的字段

set(FieldPattern)
Picks out each field set join point whose signature matches FieldPattern. [Note that the initializations of constant fields (static final fields where the initializer is a constant string object or primitive value) are not join points, since Java requires their references to be inlined.]

说明
不能捕获静态字段的修改

set捕获何时修改对象的属性

在修改字段是捕获它的值

args结合set使用

demo

将上面四个场景融合在了一起

package aspectj;

public aspect HelloWorld {
    //指定fieldPattern
    pointcut getPointcut():get(int MyClass.b);
    pointcut setPointcut():set(int MyClass.b);
    pointcut setPointcutValue(int value):set(int MyClass.b) && args(value);

    //捕获何时访问对象的属性
    before(): getPointcut()
    {
        System.out.println("get field");
        System.out.println(thisJoinPoint.getSignature());
        System.out.println(thisJoinPoint.getSourceLocation());
    }

    //捕获访问的字段值
    after() returning(int value): getPointcut() {
        System.out.println("get field value " + value);
        System.out.println(thisJoinPoint.getSignature());
        System.out.println(thisJoinPoint.getSourceLocation());
    }

    //捕获何时修改对象的属性
    before(): setPointcut() {
        System.out.println("set field");
        System.out.println(thisJoinPoint.getSignature());
        System.out.println(thisJoinPoint.getSourceLocation());
    }

    //捕获何时修改对象的值
    before(int value): setPointcutValue(value) {
        System.out.println("set field with value " + value);
        System.out.println(thisJoinPoint.getSignature());
        System.out.println(thisJoinPoint.getSourceLocation());
    }
}


package aspectj;

public class MyClass  {
    private int b;

    public static void main(String[] args) {
        MyClass myClass = new MyClass();
        myClass.b=3;
        System.out.println(myClass.b);
    }
}

输出

set field
int aspectj.MyClass.b
MyClass.java:8
set field with value 3
int aspectj.MyClass.b
MyClass.java:8
get field
int aspectj.MyClass.b
MyClass.java:9
get field value 3
int aspectj.MyClass.b
MyClass.java:9
3

很好理解

备注

FieldPattern =
[ModifiersPattern] TypePattern [TypePattern . ] IdPattern

refer

https://eclipse.org/aspectj/doc/released/progguide/semantics-pointcuts.html
https://eclipse.org/aspectj/doc/released/progguide/semantics-advice.html
《aspectj cookbook》