package com.example.demo.design.chain;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface MyChain {}

package com.example.demo.design.chain;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import java.lang.reflect.Method;
import java.util.List;

@Aspect
@Component
public class ChainHandlerAspect implements InitializingBean {
    @Autowired
    // 注入所有實(shí)現(xiàn)ChainHandler接口的責(zé)任鏈處理器
    private List<ChainHandler> chainHandlers;

    // 責(zé)任鏈的頭節(jié)點(diǎn)
    private ChainHandler chainHandler;

    @Around("@annotation(com.example.demo.design.chain.MyChain)")
    public Object checkParam(ProceedingJoinPoint pjp) throws Throwable {
        Object[] args = pjp.getArgs(); // 獲取方法的所有參數(shù)
        MethodSignature signature = (MethodSignature) pjp.getSignature();
        Method method = signature.getMethod();
        Class<?>[] parameterTypes = method.getParameterTypes(); // 獲取方法的參數(shù)類(lèi)型列表

        for (int i = 0; i < parameterTypes.length; i++) {
            if (parameterTypes[i].getName().equals("java.lang.String")) {
                chainHandler.handle(new Request((String) args[0]));
            }
        }
        return pjp.proceed();
    }

    /**
     * 構(gòu)建處理器鏈
     */
    private ChainHandler buildHandlerChain() {
        ChainHandler headChainHandler = null;
        ChainHandler currentChainHandler = null;
        for (ChainHandler chainHandler : chainHandlers) {
            if (headChainHandler == null) {
                headChainHandler = chainHandler;
                currentChainHandler = headChainHandler;
            } else {
                currentChainHandler.setNextHandler(chainHandler);
                currentChainHandler = chainHandler;
            }
        }
        return headChainHandler;
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        // 構(gòu)建責(zé)任鏈
        chainHandler = this.buildHandlerChain();
    }
}

package com.example.demo.design.chain;

public interface ChainHandler {
    void handle(Request request);

    void setNextHandler(ChainHandler handler);
}

package com.example.demo.design.chain;

import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

@Component
@Order(1)
public class FirstHandler implements ChainHandler {
    private ChainHandler nextHandler;

    @Override
    public void handle(Request request) {
        // 處理請(qǐng)求
        System.out.println("FirstHandler handling request " + request);

        // 將請(qǐng)求傳遞給下一個(gè)處理器
        if (nextHandler != null) {
            nextHandler.handle(request);
        }
    }

    @Override
    public void setNextHandler(ChainHandler handler) {
        this.nextHandler = handler;
    }
}

package com.example.demo.design.chain;

import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

@Component
@Order(2)
public class SecondHandler implements ChainHandler {
    private ChainHandler nextHandler;

    @Override
    public void handle(Request request) {
        // 處理請(qǐng)求
        System.out.println("SecondHandler handling request " + request);

        // 將請(qǐng)求傳遞給下一個(gè)處理器
        if (nextHandler != null) {
            nextHandler.handle(request);
        }
    }

    @Override
    public void setNextHandler(ChainHandler handler) {
        this.nextHandler = handler;
    }
}

package com.example.demo.design.chain;

import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

@Component
@Order(3)
public class ThirdHandler implements ChainHandler {
    private ChainHandler nextHandler;

    @Override
    public void handle(Request request) {
        // 處理請(qǐng)求
        System.out.println("ThirdHandler handling request " + request);
    }

    @Override
    public void setNextHandler(ChainHandler handler) {
        this.nextHandler = handler;
    }
}

package com.example.demo.design.chain;

public class Request {
    private String data;

    public Request(String data) {
        this.data = data;
    }

    public String getData() {
        return data;
    }

    public void setData(String data) {
        this.data = data;
    }

    @Override
    public String toString() {
        return "Request{" +
                "data='" + data + ''' +
                '}';
    }
}

package com.example.demo.design.chain;

import org.springframework.stereotype.Component;

@Component
public class BizComponent {
    @MyChain
    public void process(String data) {
        System.out.println(data);
    }
}

package com.example.demo.design.chain;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.EnableAspectJAutoProxy;

@SpringBootApplication
@EnableAspectJAutoProxy
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(com.example.demo.design.chain.Application.class, args);
    }
}

package com.example.demo.design.chain;

import lombok.Data;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;

@Component
@Data
public class ComponentRunner implements CommandLineRunner {

    @Autowired
    private BizComponent bizComponent;

    @Override
    public void run(String... args) throws Exception {
        // 執(zhí)行某個(gè)方法（帶Chain注解）
        bizComponent.process("Hello world!");
    }
}