aop链式调用

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多个aop如果叠加
采用了责任链的模式

使用ConcerteHandler实现类实现HandleProcess接口同时这个实现类又组合了这个接口，通过successor判断来进行链式调用

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首先我们新建一个Handler

public abstract class Handler {

    private Handler successor;

    public Handler getSuccessor() {
        return successor;
    }

    public void setSuccessor(Handler successor) {
        this.successor = successor;
    }

    public void execute(){
        handleProcess();
        if(successor != null){
            successor.execute();
        }
    }

    protected abstract void handleProcess();
}

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下面我们看看client端实现

public class ChainClient {
    static class HandlerA extends Handler{

        @Override
        protected void handleProcess() {
            System.out.println("handler by a");
        }
    }

    static class HandlerB extends Handler{

        @Override
        protected void handleProcess() {
            System.out.println("handler by b");
        }
    }

    static class HandlerC extends Handler{

        @Override
        protected void handleProcess() {
            System.out.println("handler by c");
        }
    }

    public static void main(String[] args) {
        Handler handlerA = new HandlerA();
        Handler handlerB = new HandlerB();
        Handler handlerC = new HandlerC();
        handlerA.setSuccessor(handlerB);
        handlerB.setSuccessor(handlerC);
        handlerA.execute();
    }
}

由此我们实现了链式调用，但是我们也发现了每次都需要设置从属关系。

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下面我们对上面方法改造，使用另外一个Chain对再下面的代码进行一次封装

public static void main(String[] args) {
    Handler handlerA = new HandlerA();
    Handler handlerB = new HandlerB();
    Handler handlerC = new HandlerC();
    handlerA.setSuccessor(handlerB);
    handlerB.setSuccessor(handlerC);
    handlerA.execute();
}

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下面我们新建一个ChainHandler

public abstract class ChainHandler {

    public void execute(Chain chain){
        handleProcess();
        chain.proceed();
    }
    protected abstract void handleProcess();
}

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Chain对链式关系封装起来

public class Chain {
    private List<ChainHandler> handlers;

    private int index = 0;

    public Chain(List<ChainHandler> handlers) {
        this.handlers = handlers;
    }
    public void proceed(){
        if(index >= handlers.size()){
            return;
        }
        handlers.get(index++).execute(this);
    }
}

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下面我们看一下如何实现调用类

public class ChainClient {
    static class ChainHandlerA extends ChainHandler{
        @Override
        protected void handleProcess() {
            System.out.println("handler by chain a");
        }
    }
    static class ChainHandlerB extends ChainHandler{
        @Override
        protected void handleProcess() {
            System.out.println("handler by chain b");
        }
    }
    static class ChainHandlerC extends ChainHandler{
        @Override
        protected void handleProcess() {
            System.out.println("handler by chain c");
        }
    }
    public static void main(String[] args) {
        List<ChainHandler> handlers = Arrays.asList(
                new ChainHandlerA(),
                new ChainHandlerB(),
                new ChainHandlerC()
        );
        Chain chain = new Chain(handlers);
        chain.proceed();
    }
}