责任链模式（Chain of Responsibility Pattern）案例（二）

向右看齐 2024-03-22 11:00 20阅读 0赞

责任链模式（Chain of Responsibility Pattern）是一种行为型设计模式，它允许多个对象作为一个链式结构进行处理。 当请求从一个对象传递到另一个对象时，这些对象可以依次处理请求或将其传递给下一个对象，直到该请求被处理或直到最终没有对象处理请求。

举例来说，想象你要申请一份文件，需要经过三个级别的审批：部门经理、总经理和董事长。每个级别的领导都有不同的权限，如果当前级别无法处理请求，则将请求传递给下一个级别的领导。

让我们看一个基于JAVA的责任链模式的示例代码：

//抽象处理者：领导
    abstract class Leader {
        
        protected String name;
        protected Leader nextLeader; // 上级领导
    
        public Leader(String name) {
        
            this.name = name;
        }
    
        //设置上级领导
        public void setNextLeader(Leader leader) {
        
            this.nextLeader = leader;
        }
    
        //处理请求
        public abstract void handleRequest(LeaveRequest request);
    }
    
    //具体处理者1：部门经理
    class Director extends Leader {
        
    
        public Director(String name) {
        
            super(name);
        }
    
        @Override
        public void handleRequest(LeaveRequest request) {
        
            if (request.getLeaveDays() <= 3) {
        
                System.out.println("员工：" + request.getName() + "请假，天数：" + request.getLeaveDays() + "，理由：" + request.getReason());
                System.out.println("部门经理：" + this.name + "，审批通过！");
            } else {
        
                if (this.nextLeader != null) {
        
                    this.nextLeader.handleRequest(request);
                }
            }
        }
    }
    
    //具体处理者2：总经理
    class Manager extends Leader {
        
    
        public Manager(String name) {
        
            super(name);
        }
    
        @Override
        public void handleRequest(LeaveRequest request) {
        
            if (request.getLeaveDays() <= 10) {
        
                System.out.println("员工：" + request.getName() + "请假，天数：" + request.getLeaveDays() + "，理由：" + request.getReason());
                System.out.println("总经理：" + this.name + "，审批通过！");
            } else {
        
                if (this.nextLeader != null) {
        
                    this.nextLeader.handleRequest(request);
                }
            }
        }
    }
    
    //具体处理者3：董事长
    class Chairman extends Leader {
        
    
        public Chairman(String name) {
        
            super(name);
        }
    
        @Override
        public void handleRequest(LeaveRequest request) {
        
            if (request.getLeaveDays() <= 30) {
        
                System.out.println("员工：" + request.getName() + "请假，天数：" + request.getLeaveDays() + "，理由：" + request.getReason());
                System.out.println("董事长：" + this.name + "，审批通过！");
            } else {
        
                System.out.println("员工：" + request.getName() + "请假，天数：" + request.getLeaveDays() + "，理由：" + request.getReason());
                System.out.println("董事长：" + this.name + "，审批不通过！");
            }
        }
    }
    
    //请求类
    class LeaveRequest {
        
        private String name;
        private int leaveDays;
        private String reason;
    
        public LeaveRequest(String name, int leaveDays, String reason) {
        
            this.name = name;
            this.leaveDays = leaveDays;
            this.reason = reason;
        }
    
        public String getName() {
        
            return name;
        }
    
        public int getLeaveDays() {
        
            return leaveDays;
        }
    
        public String getReason() {
        
            return reason;
        }
    }
    
    //客户端代码
    public class Client {
        
        public static void main(String[] args) {
        
            //创建责任链上的对象
            Leader director = new Director("张三");
            Leader manager = new Manager("李四");
            Leader chairman = new Chairman("王五");
    
            //设置链中的顺序
            director.setNextLeader(manager);
            manager.setNextLeader(chairman);
    
            //提交请求
            LeaveRequest request1 = new LeaveRequest("小明", 2, "身体不舒服");
            director.handleRequest(request1);
    
            Leave  Request request2 = new LeaveRequest("小红", 5, "外出旅游");
            director.handleRequest(request2);
    
            LeaveRequest request3 = new LeaveRequest("小李", 20, "家里有事");
            director.handleRequest(request3);
    
            LeaveRequest request4 = new LeaveRequest("小张", 35, "创业");
            director.handleRequest(request4);
        }
    }

输出结果为：

员工：小明请假，天数：2，理由：身体不舒服
    部门经理：张三，审批通过！
    员工：小红请假，天数：5，理由：外出旅游
    总经理：李四，审批通过！
    员工：小李请假，天数：20，理由：家里有事
    董事长：王五，审批通过！
    员工：小张请假，天数：35，理由：创业
    董事长：王五，审批不通过！

从中可以看到，当请假天数超过部门经理和总经理权限时，请求会依次传递给下一级领导，直到被最终的董事长处理。这就是责任链模式的应用。