设计模式-职责链模式

职责链模式

责任链模式（Chain of Responsibility Pattern）为请求创建了一个接收者对象的链。这种模式给予请求的类型，对请求的发送者和接收者进行解耦。这种类型的设计模式属于行为型模式。

责任链模式通过将多个处理器（处理对象）以链式结构连接起来，使得请求沿着这条链传递，直到有一个处理器处理该请求为止。

责任链模式允许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。将这些对象连成一条链，并沿着这条链传递请求，直到有一个对象处理它为止。

类图示例

举个例子

申请加薪

代码实现

//请求类
class Request{
    private String requestType;

    public String getRequestType() {
        return requestType;
    }

    public void setRequestType(String requestType) {
        this.requestType = requestType;
    }
    private String requestContent;
    public String getRequestContent() {
        return requestContent;
    }
    public void setRequestContent(String requestContent) {
        this.requestContent = requestContent;
    }
    private int numberOfRequests;
    public int getNumberOfRequests() {
        return numberOfRequests;
    }
    public void setNumberOfRequests(int numberOfRequests) {
        this.numberOfRequests = numberOfRequests;
    }
}
//抽象管理者
abstract class Manager{
    protected String name;
    protected Manager superior;
    public Manager(String name){
        this.name = name;
    }
    public void SetSuperior(Manager superior){
        this.superior = superior;
    }
    abstract void RequestApplications(Request request);
}
//经理
class CommonManager extends Manager{
    public CommonManager(String name){
        super(name);
    }
    public void RequestApplications(Request request){
        if(request.getRequestType() == "请假"&&request.getNumberOfRequests() < 2){
            System.out.println(name+" "+request.getRequestContent()+" "+request.getNumberOfRequests()+"被批准");
        }else{
            if (superior != null){
                superior.RequestApplications(request);
            }
        }
    }
}
//总监
class MajordomoManager extends Manager{
    public MajordomoManager(String name){
        super(name);
    }
    public void RequestApplications(Request request){
        if(request.getRequestType() == "请假"&&request.getNumberOfRequests() < 5){
            System.out.println(name+" "+request.getRequestContent()+" "+request.getNumberOfRequests()+"被批准");
        }else{
            if (superior != null){
                superior.RequestApplications(request);
            }
        }
    }
}
//总经理
class GeneralManager extends Manager{
    public GeneralManager(String name){
        super(name);
    }
    public void RequestApplications(Request request){
        if(request.getRequestType()=="请假"){
            System.out.println(name+" "+request.getRequestContent()+" "+request.getNumberOfRequests()+"被批准");
        }else if(request.getRequestType()=="加薪"&&request.getNumberOfRequests() <= 500){
            System.out.println(name+" "+request.getRequestContent()+" "+request.getNumberOfRequests()+"被批准");
        }else if(request.getRequestType()=="加薪"&&request.getNumberOfRequests() > 500){
            System.out.println(name+" "+request.getRequestContent()+" "+request.getNumberOfRequests()+"再说吧");
        }
    }
}

public class ChainOfDuty {
    public static void main(String[] args) {
        CommonManager jinli=new CommonManager("金利");
        MajordomoManager zongjian = new MajordomoManager("宗剑");
        GeneralManager zongjingli = new GeneralManager("钟精力");
        jinli.SetSuperior(zongjian);
        zongjian.SetSuperior(zongjingli);

        Request request=new Request();
        request.setRequestType("请假");
        request.setRequestContent("zhang3请假");
        request.setNumberOfRequests(1);
        jinli.RequestApplications(request);

        Request request2=new Request();
        request2.setRequestType("请假");
        request2.setRequestContent("zhang3请假");
        request2.setNumberOfRequests(4);
        jinli.RequestApplications(request2);

        Request request3=new Request();
        request3.setRequestType("加薪");
        request3.setRequestContent("zhang3加薪");
        request3.setNumberOfRequests(500);
        jinli.RequestApplications(request3);

        Request request4=new Request();
        request4.setRequestType("加薪");
        request4.setRequestContent("zhang3加薪");
        request4.setNumberOfRequests(1000);
        jinli.RequestApplications(request4);
    }
}

类图

职责链模式包含如下角色

1. Handler接口：定义一个方法用于处理请求。
2. ConcreteHandler类：实现Handler接口，包含请求处理逻辑和对下一个处理者的引用。

模式分析

• 优点
  1. 降低耦合度：发送者和接收者之间解耦。
  2. 简化对象：对象不需要知道链的结构。
  3. 灵活性：通过改变链的成员或顺序，动态地新增或删除责任。
  4. 易于扩展：增加新的请求处理类很方便。
• 缺点
  1. 请求未被处理：不能保证请求一定会被链中的某个处理者接收。
  2. 性能影响：可能影响系统性能，且调试困难，可能导致循环调用。
  3. 难以观察：运行时特征不明显，可能妨碍除错。