AspectJ构造函数强制工厂模式 [英] AspectJ constructor force factory pattern

问题描述

我想将对象返回从调用更改为构造函数

I want to change the object return from call to a constuctor

FROM

public class A  {

   public A(){
   }

   public String sayHello() {
    return "hello";
   }

   public String foo() {
      return "foo";
   }

}

TO

public class AWrapped extends A {

     private A wrapped;

     public AWrapped() {
       super();
     }


     public AWrapped(A pWrapped) {
        wrapped=pWrapped;
     }

     public String foo() {
       return wrapped.foo();
     }

     public String sayHello {
        return "gday mate";
     }

}

我想做的是更改从通话中返回的对象

What i want to do is to change the object that is returned from a call

A a = new A();
a.sayHello() returns "gday mate"

a是AWrapped的实例

a is an instaceof AWrapped

我知道这通常是通过工厂模式完成的，但我无法访问A的代码或创建新A的代码。并且有1000个地方可以创建A.

I understand that this would usually be done with a factory pattern but I dont have access to the code of A or the code that makes new A's. And there are 1000s of places that A can be created.

似乎Aspectj可能会做到这一点，但我不太了解它，如果AspectJ会做的伎俩如何绕过无限包装我需要知道它是从内部和方面构建的，所以它不会再次包裹它。

It seems that Aspectj might do the trick, but i dont know much about it, If AspectJ would do the trick how to I get around the infinite wrapping i need to know that its being consturcted from within and aspect so it doesnt wrapp it again.

感谢您的帮助
Jon

Thanks for the help Jon

推荐答案

如果我理解你，你可以做以下事情：

If I understand you right you could do the following:

我创建了三个包：

• 方面的aspectj和AWrapped.java


• 未知的A.java（可能也是Bytecode，但你必须使用加载时间编织）


• 主要测试 A a =新A（）;

• aspectj for the aspect and AWrapped.java
• unknown for A.java (could also be Bytecode but then you have to use Load Time Weaving)
• main to test A a = new A();

MyAspect如果<$ c $，则返回AWrapped对象c> new（）在A类上进行调用：

MyAspect to return the AWrapped object if a new() call is made on class A:

package aspectj;

import unknown.A;

@Aspect
public class MyAspect {

    @Pointcut("call(unknown.A.new(..)) && !within(aspectj..*)")
    public static void init(ProceedingJoinPoint pjp) {
    }

    @Around("init(pjp)")
    public Object initAdvice(ProceedingJoinPoint pjp) throws Throwable{
        Object ret = pjp.proceed();
        return new AWrapped((A) ret);
        }

}

进行测试：

package main;

import unknown.A;

public class Main {

    public static void main(String[] args) {
        A a = new A();
        System.out.println(a.sayHello());
    }
}

此输出：

gday mate

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