责任链模式的一个应用

这里写自定义目录标题

概念
应用
例子

概念

责任链模式（Chain of Responsibility Pattern）为请求创建了一个接收者对象的链，使多个对象都有机会处理同一个请求。这种模式中请求的发送者和接收者，以及接收者间都是解耦的。

应用

过滤器
复杂的ifelse判断，选用于判断条件和内容都复杂，或者内容复杂的情况
OA系统中的审批

例子

之前看到这个模式感觉很适合现在项目中运输路线的规划，所以写了一个小demo
背景：假设根据实际运输的距离来判断生成运输路线使用哪种方案，距离小于10千米，不用调拔，10千米<距离<20千米,一级调拔，20千米<距离<30千米,二级调拔（当初实际情况是很复杂的）

1.创建一个请求对象

public class TranslineQueryParam {
    private Integer distance;

    public Integer getDistance() {
        return distance;
    }

    public void setDistance(Integer distance) {
        this.distance = distance;
    }
}

2.创建一个接收对象

public class TranslineResult {
    private String info;

    public String getInfo() {
        return info;
    }
    public void setInfo(String info) {
        this.info = info;
    }
}

3.创建一个Handler

public abstract class TranslineQueryHandler {
    //这个变量主要是给各个Handler起个名字，方便调试
    private String name;
    //这个字段一定要有,指定下一处理者
    private TranslineQueryHandler nextTranslineQueryHandler;

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

    public TranslineQueryHandler(String name){
        this.name=name;
    }

    public TranslineQueryHandler getNextTranslineQueryHandler() {
        return nextTranslineQueryHandler;
    }

    //给当前对象指定下一处理人，并返回【下一处理人】
    public TranslineQueryHandler setNextTranslineQueryHandler(TranslineQueryHandler next) {
        this.nextTranslineQueryHandler = next;
        System.out.println("-----处理人------"+this+"-----的下一处理人-----"+next);
        return next;
    }
    public String toString() {              // 显示字符串
        return "[" + name + "]";
    }

    //抽象方法deal：用于处理请求，所有处理人都要根据自身条件重写此方法
    public abstract TranslineResult deal(TranslineQueryParam translineQueryParam);

    //核心方法doChain:如果当前TranslineQueryHandler可以解决，就解决，如果不行，就调此方法交给next去解决
    protected void doChain(TranslineQueryParam translineQueryParam){
        if(this.nextTranslineQueryHandler != null){
            this.nextTranslineQueryHandler.deal(translineQueryParam);
        }
    }

}

4.创建责任链中的三个对象
对象一：不需要调拔

public class NoNeedWarehousesCross extends TranslineQueryHandler{

    public NoNeedWarehousesCross(String name) {
        super(name);
    }

    @Override
    public TranslineResult deal(TranslineQueryParam translineQueryParam) {
        TranslineResult translineResult =new TranslineResult();
        if(translineQueryParam.getDistance()<10){
            System.out.println("--------------不需要调拔就可以找到运输路线-----------------------");
            translineResult.setInfo("--------------不需要调拔就可以找到运输路线-----------------------");
        }else {
            System.out.println("--------------进入调拔逻辑-----------------------");
            translineResult.setInfo("--------------进入调拔逻辑-----------------------");
            this.doChain(translineQueryParam);
        }
        return translineResult;

    }
}

对象二：一级调拔

public class OneTimeWarehousesCross extends TranslineQueryHandler{
    public OneTimeWarehousesCross(String name) {
        super(name);
    }

    @Override
    public TranslineResult deal(TranslineQueryParam translineQueryParam) {
        TranslineResult translineResult = new TranslineResult();
        if(translineQueryParam.getDistance()<20){
            System.out.println("--------------一级调拔可以找到运输路线-----------------------");
            translineResult.setInfo("--------------一级调拔可以找到运输路线-----------------------");
        }else {
            System.out.println("--------------进入二级调拔-----------------------");
            translineResult.setInfo("--------------进入二级调拔-----------------------");
            this.doChain(translineQueryParam);
        }
        return translineResult;
    }
}

对象三：二级调拔

public class TwoTimeWarehousesCross extends TranslineQueryHandler{
    public TwoTimeWarehousesCross(String name) {
        super(name);
    }

    @Override
    public TranslineResult deal(TranslineQueryParam translineQueryParam) {
        TranslineResult  translineResult = new TranslineResult();
        if(translineQueryParam.getDistance()<30){
            System.out.println("--------------两级调拔可以找到运输路线-----------------------");
            translineResult.setInfo("--------------两级调拔可以找到运输路线-----------------------");
        }else {
            System.out.println("--------------找不到运输路线-----------------------");
            translineResult.setInfo("--------------找不到运输路线-----------------------");
            this.doChain(translineQueryParam);
        }
        return translineResult;
    }
}

5.将这些对象组装并测试

public class TranslinesCalculate {

    public static void main(String[] args) {
        NoNeedWarehousesCross noNeedWarehousesCross = new NoNeedWarehousesCross("no");
        OneTimeWarehousesCross oneTimeWarehousesCross = new OneTimeWarehousesCross("one");
        TwoTimeWarehousesCross twoTimeWarehousesCross = new TwoTimeWarehousesCross("two");

        //组装责任链
        noNeedWarehousesCross.setNextTranslineQueryHandler(oneTimeWarehousesCross).setNextTranslineQueryHandler(twoTimeWarehousesCross);

        //链头部开始执行
        TranslineQueryParam translineQueryParam = new TranslineQueryParam();
        translineQueryParam.setDistance(18);
        noNeedWarehousesCross.deal(translineQueryParam);
    }
}

6.结果
责任链模式的一个应用