大话设计模式之职责链模式总结-java实现

注：示例来自《大话设计模式》

假如现有如下场景 员工向经理申请加薪或请假 经理没权利 然后向总监上报 总监也没权限 向总经理上报 我们用代码来实现这个场景 简单代码实现如下

申请类

package Test24;

//申请
public class Request {

    //申请类别
    private String requestType;
    //申请内容
    private String requestContent;
    //数量
    private int number;
    public String getRequestType() {
        return requestType;
    }
    public void setRequestType(String requestType) {
        this.requestType = requestType;
    }
    public String getRequestContent() {
        return requestContent;
    }
    public void setRequestContent(String requestContent) {
        this.requestContent = requestContent;
    }
    public int getNumber() {
        return number;
    }
    public void setNumber(int number) {
        this.number = number;
    }

}

管理者类

package Test24;

//管理者
public class Manager {

    protected String name;

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

    //得到结果
    public void GetResult(ManagerLevel managerLevel, Request request)
    {
        if (managerLevel == ManagerLevel.经理)
        {
            if (request.getRequestType() == "请假" && request.getNumber() <= 2)
            {
                System.out.println(name+":"+request.getRequestType()+" 数量"+request.getNumber()+" 被批准");
            }
            else
            {
                System.out.println(name+":"+request.getRequestType()+" 数量"+request.getNumber()+" 我无权处理");
            }

        }
        else if (managerLevel == ManagerLevel.总监)
        {
            if (request.getRequestType() == "请假" && request.getNumber() <= 5)
            {
                System.out.println(name+":"+request.getRequestType()+" 数量"+request.getNumber()+" 被批准");
            }
            else
            {
                System.out.println(name+":"+request.getRequestType()+" 数量"+request.getNumber()+" 我无权处理");
            }
        }
        else if (managerLevel == ManagerLevel.总经理)
        {
            if (request.getRequestType() == "请假")
            {
                System.out.println(name+":"+request.getRequestType()+" 数量"+request.getNumber()+" 被批准");
            }
            else if (request.getRequestType() == "加薪" && request.getNumber() <= 500)
            {
                System.out.println(name+":"+request.getRequestType()+" 数量"+request.getNumber()+" 被批准");
            }
            else if (request.getRequestType() == "加薪" && request.getNumber() > 500)
            {
                System.out.println(name+":"+request.getRequestType()+" 数量"+request.getNumber()+" 再说吧");
            }
        }

    }

}

管理者级别类

package Test24;

public enum ManagerLevel {

    经理,总监,总经理

}

客户端代码

package Test24;

public class Program {

    public static void main(String[] args) {

        Manager jinli = new Manager("金利");
        Manager zongjian = new Manager("宗剑");
        Manager zhongjingli = new Manager("钟精励");

        Request request = new Request();
        request.setRequestType("加薪");
        request.setRequestContent("小菜请求加薪");
        request.setNumber(1000);

        jinli.GetResult(ManagerLevel.经理, request);
        zongjian.GetResult(ManagerLevel.总监, request);
        zhongjingli.GetResult(ManagerLevel.总经理, request);

        Request request2 = new Request();
        request2.setRequestType("请假");
        request2.setRequestContent("小菜请假");
        request2.setNumber(3);

        jinli.GetResult(ManagerLevel.经理, request2);
        zongjian.GetResult(ManagerLevel.总监, request2);
        zhongjingli.GetResult(ManagerLevel.总经理, request2);

    }

}

上面的写法 管理这类里面的结果方法比较长 加上有太多的分支判断 是非常不好的设计 违背了单一职责原则和开放-封闭原则 下面我们使用职责链模式进行重构 代码如下

管理者类

package Test24;

//管理者
public abstract class Manager {

    protected String name;
    //管理者的上级
    protected Manager superior;

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

    //设置管理者的上级
    public void SetSuperior(Manager superior)
    {
        this.superior = superior;
    }

    //申请请求
    abstract public void RequestApplications(Request request);

}

经理类

package Test24;

//经理
public class CommonManager extends Manager {

    public CommonManager(String name) {
        super(name);

    }

    @Override
    public void RequestApplications(Request request) {
        if (request.getRequestType() == "请假" && request.getNumber() <= 2)
        {
            System.out.println(name+":"+request.getRequestType()+" 数量"+request.getNumber()+" 被批准");
        }
        else
        {
            if (superior != null)
                superior.RequestApplications(request);
        }

    }

}

总监类

package Test24;

//总监
public class Majordomo extends Manager {

    public Majordomo(String name) {
        super(name);

    }

    @Override
    public void RequestApplications(Request request) {
        if (request.getRequestType() == "请假" && request.getNumber() <= 5)
        {
            System.out.println(name+":"+request.getRequestType()+" 数量"+request.getNumber()+" 被批准");
        }
        else
        {
            if (superior != null)
                superior.RequestApplications(request);
        }

    }

}

总经理类

package Test24;

//总经理
public class GeneralManager extends Manager {

    public GeneralManager(String name) {
        super(name);

    }

    @Override
    public void RequestApplications(Request request) {
        if (request.getRequestType() == "请假")
        {
            System.out.println(name+":"+request.getRequestType()+" 数量"+request.getNumber()+" 被批准");
        }
        else if (request.getRequestType() == "加薪" && request.getNumber() <= 500)
        {
            System.out.println(name+":"+request.getRequestType()+" 数量"+request.getNumber()+" 被批准");
        }
        else if (request.getRequestType() == "加薪" && request.getNumber() > 500)
        {
            System.out.println(name+":"+request.getRequestType()+" 数量"+request.getNumber()+" 再说吧");
        }

    }

}

客户端代码

package Test24;

public class Program {

    public static void main(String[] args) {

        CommonManager jinli = new CommonManager("金利");
        Majordomo zongjian = new Majordomo("宗剑");
        GeneralManager zhongjingli = new GeneralManager("钟精励");
        jinli.SetSuperior(zongjian);
        zongjian.SetSuperior(zhongjingli);

        Request request = new Request();
        request.setRequestType("请假");
        request.setRequestContent("小菜请假");
        request.setNumber(1);
        jinli.RequestApplications(request);

        Request request2 = new Request();
        request2.setRequestType("请假");
        request2.setRequestContent("小菜请假");
        request2.setNumber(4);
        jinli.RequestApplications(request2);

        Request request3 = new Request();
        request3.setRequestType("加薪");
        request3.setRequestContent("小菜请求加薪");
        request3.setNumber(500);
        jinli.RequestApplications(request3);

        Request request4 = new Request();
        request4.setRequestType("加薪");
        request4.setRequestContent("小菜请求加薪");
        request4.setNumber(1000);
        jinli.RequestApplications(request4);

    }

}

这样就很好地解决了原来大量的分支判断造成的难维护 灵活性差的问题

职责链模式 使多个对象都有机会处理请求 从而避免请求的发送者和接收者之间的耦合关系 将这个对象连成一条链 并沿着这条链传递该请求 直到有一个对象处理它为止

职责链的好处 当客户提交一个请求时 请求是沿链传递直至有一个ConcreteHandler对象负责处理它
接收者和发送者都没有对方的明确信息 且链中的对象自己也并不直到链的结构 结果是职责链可简化对象的相互连接 它们仅需保持一个指向其后继者的引用 而不需保持它所有的候选接受者的引用
可以随时地增加或修改处理一个请求的结构 增强了给对象指派职责的灵活性

缺点 一个请求极有可能到了链的末端都得不到处理 或者因为没有正确配置而得不到处理

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