spring aop学习9:Aop的链式调用(责任链模式)

逃离我推掉我的手 2022-06-06 04:51 192阅读 0赞

**一.责任链模式**  
1.基本的责任链模式  
◆主体父类:abstract class Subject.java

package com.tiglle.responsibility.chain.model;
    //主体
    public abstract class Subject {
    
        private Subject successor;
    
        protected abstract void handle();
    
        public void execute(){
            handle();
            if(successor!=null){
                successor.execute();
            }
        }
    
        public Subject getSuccessor() {
            return successor;
        }
    
        public void setSuccessor(Subject successor) {
            this.successor = successor;
        }
    
    }

◆子类和测试main方法:MainExec.java

package com.tiglle.responsibility.chain.model;
    
    public class MainExec { 
    
        private static class Part1 extends Subject{ 
            @Override
            protected void handle() {
                System.out.println("Part1的handle");
            }
        }
        private static class Part2 extends Subject{ 
            @Override
            protected void handle() {
                System.out.println("Part2的handle");
            }
        }
        private static class Part3 extends Subject{ 
            @Override
            protected void handle() {
                System.out.println("Part3的handle");
            }
        }
    
    
        public static void main(String[] args) {
            Part1 part1 = new Part1();
            Part2 part2 = new Part2();
            Part3 part3 = new Part3();
    
            part1.setSuccessor(part2);
            part2.setSuccessor(part3);
    
            part1.execute();
        }
    
    }
    
    执行结果:
    Part1的handle
    Part2的handle
    Part3的handle

原理:  
执行Part1继承自父类的execute()方法，首先执行Part1重写了父类抽象方法handle()，然后判断successor(此时successor为Part2)是否为null

此时successor(Part2)不为null，执行Part2的execute，首先执行Part2重写了父类抽象方法handle()，然后判断successor(此时successor为Part3)是否为null

此时successor(Part3)不为null，执行Part3的execute，首先执行Part3重写了父类抽象方法handle()，然后判断successor(Part3的successor为null)是否为null，为null，停止执行

2.优化的责任链模式  
◆主体父类:abstract class Subject.java

package com.tiglle.responsibility.chain.model.optimization;
    
    public abstract class Subject {
    
        protected abstract void handle();
    
        public void execute(SubjectChain successor){
            handle();
            successor.process();
        }
    }

◆中间类:class SubjectChain.java

package com.tiglle.responsibility.chain.model.optimization;
    
    import java.util.List;
    
    public class SubjectChain {
    
        private List<Subject> successors;
    
        public SubjectChain(List<Subject> successors){
            this.successors = successors;
        }
    
        private int index = 0;
    
        public void process(){
            if(index < successors.size()){
                successors.get(index++).execute(this);
            }
        }
    }

◆测试main方法:MainExec.java

package com.tiglle.responsibility.chain.model.optimization;
    
    import java.util.ArrayList;
    import java.util.List;
    
    public class MainExec { 
    
        private static class Part1 extends Subject{ 
            @Override
            protected void handle() {
                System.out.println("Part1的handle");
            }
        }
    
        private static class Part2 extends Subject{ 
            @Override
            protected void handle() {
                System.out.println("Part2的handle");
            }
        }
    
        private static class Part3 extends Subject{ 
            @Override
            protected void handle() {
                System.out.println("Part3的handle");
            }
        }
    
        public static void main(String[] args) {
            Part1 part1 = new Part1();
            Part2 part2 = new Part2();
            Part3 part3 = new Part3();
            List<Subject> successors = new ArrayList<>();
            successors.add(part1);
            successors.add(part2);
            successors.add(part3);
    
            SubjectChain subjectChain = new SubjectChain(successors);
            subjectChain.process();
        }
    }
    
    
    执行结果:
    Part1的handle
    Part2的handle
    Part3的handle

原理:两个方法的互相调用，并设置中断条件

二.spring aop的链式调用使用的第二种方法:  
源码:

@Override
        public Object proceed() throws Throwable {
            // We start with an index of -1 and increment early.
            //从-1开始每次加1
            if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {
                return invokeJoinpoint();
            }
    
            Object interceptorOrInterceptionAdvice =
                    this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex);
            if (interceptorOrInterceptionAdvice instanceof InterceptorAndDynamicMethodMatcher) {
                // Evaluate dynamic method matcher here: static part will already have
                // been evaluated and found to match.
                InterceptorAndDynamicMethodMatcher dm =
                        (InterceptorAndDynamicMethodMatcher) interceptorOrInterceptionAdvice;
                //
                if (dm.methodMatcher.matches(this.method, this.targetClass, this.arguments)) {
                    return dm.interceptor.invoke(this);
                }else {
                    // Dynamic matching failed.
                    // Skip this interceptor and invoke the next in the chain.
                    return proceed();
                }
            }else {
                // It's an interceptor, so we just invoke it: The pointcut will have
                // been evaluated statically before this object was constructed.
                return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);
            }
        }