设计模式之责任链设计模式

一、概念

• 责任链模式就是一件事多个对象处理，只有一个对象处理成功；

二、场景

• NET 中的中间件就是使用责任链模式。
• 用户登录[账号登录\手机验证登录]都得对用户进行验证是否存在、是否锁定、密码是否正确；
• 员工请假需要各级领导审批；

三、实现

• 条件
  • java
• 场景
  • 以员工请假，多级领导[部门主管、部门经理、老板]审批为场景。
• 实现
  • 领域模型类，类名：Leave.java

        package com.ResponsibilityChainPattern;
        public class Leave {
        
            private  int Days;
            private String Name;
        
            public int getDays() {
                return Days;
            }
            public String getName() {
                return Name;
            }
            public void setDays(int days) {
                Days = days;
            }
            public void setName(String name) {
                Name = name;
            }
        }    
    

  • 部门主管类，类名：DepartmentLeader.java

        package com.ResponsibilityChainPattern;
        public class DepartmentLeader extends AbstractLeave implements  ILeaveHandler {
            private final  int MAX_DAYS = 3;
        
            public DepartmentLeader(String _Name)
            {
                Name = _Name;
            }
        
            @Override
            public void LeaveHandler(Leave leave) {
                if (leave.getDays()<= MAX_DAYS)
                {
                    System.out.print(Name+"审批成功，流程已走完！");
                    return ;
                }
                if (leaveHandler != null)
                {
                    leaveHandler.LeaveHandler(leave);
                }
            }
        }   
    

  • 部门经理类，类名：DepartmentManager.java

        package com.ResponsibilityChainPattern;
        public class DepartmentManager  extends AbstractLeave  implements  ILeaveHandler{
            private final  int MAX_DAYS = 10;
        
            public DepartmentManager(String _Name)
            {
                Name = _Name;
            }
        
            @Override
            public void LeaveHandler(Leave leave) {
               if(leave.getDays()<= MAX_DAYS)
               {
                   System.out.print(Name+"审批成功，流程已走完！");
                   return;
               }
                if (leaveHandler != null)
                {
                    leaveHandler.LeaveHandler(leave);
                }
            }
        }    
    

  • 老板类，类名：Boss.java

        package com.ResponsibilityChainPattern;
        public class Boss extends AbstractLeave implements  ILeaveHandler {
            private final int MAX_DAYS = 30;
        
            public Boss(String _Name)
            {
                Name = _Name;
            }
            @Override
            public void LeaveHandler(Leave leave) {
               if(leave.getDays()<= MAX_DAYS)
               {
                   System.out.print(Name+"审批成功，流程已走完！");
                   return;
               }
            }
        }
    
    

  • 接口类，类名：ILeaveHandler.java

        package com.ResponsibilityChainPattern;
        public interface ILeaveHandler {
            void LeaveHandler(Leave leave);
        } 
    

  • 抽象类，类名：AbstractLeave.java

        package com.ResponsibilityChainPattern;
        public abstract class AbstractLeave {
            protected String  Name;
            protected ILeaveHandler  leaveHandler;
            public ILeaveHandler getLeaveHandler() {
                return leaveHandler;
            }
            public void setLeaveHandler(ILeaveHandler leaveHandler) {
                this.leaveHandler = leaveHandler;
            }
        
        }    
    

  • 入口类，类名：Main

        package com; 
         
        import com.ResponsibilityChainPattern.Boss;
        import com.ResponsibilityChainPattern.DepartmentLeader;
        import com.ResponsibilityChainPattern.DepartmentManager;
        import com.ResponsibilityChainPattern.Leave;
        
        public class Main { 
            public static void main(String[] args) { 
                Leave  leave= new Leave();
                leave.setDays(20);
                leave.setName("小明");
                // 创建角色
                DepartmentLeader dl =new DepartmentLeader("部主管");
                DepartmentManager dm = new DepartmentManager("部门经理");
                Boss boss= new Boss("老板");
                //审批
                dl.setLeaveHandler(dm);
                dm.setLeaveHandler(boss);
                dl.LeaveHandler(leave);
            }
        }    
    

四、优缺点

• 优点
  • 降低耦合度。它将请求的发送者和接收者解耦。
  • 简化了对象。使得对象不需要知道链的结构。
  • 增强给对象指派职责的灵活性。通过改变链内的成员或者调动它们的次序，允许动态地新增或者删除责任。
  • 增加新的请求处理类很方便。
• 缺点
  • 不能保证请求一定被接收。
  • 系统性能将受到一定影响，而且在进行代码调试时不太方便，可能会造成循环调用。
  • 可能不容易观察运行时的特征，有碍于除错。