设计模式学习—前端控制器模式(Front Controller Design Pattern)

淡淡的烟草味﹌ 2022-06-09 14:54 152阅读 0赞

# 一、我的理解 #

前端控制器模式将所有请求集中到一个类处理，由该类依据不同的请求来执行相应的动作。

# 二、实现方式 #

类似于分发模式，前端控制器类接收请求，然后判断请求类型，根据请求类型调用响应的接口。

# 三、实例 #

![Center][]

###### Java实例 ######

StudentView类：前端页面一

package com.study.dp.frontcontroller;
    
    public class StudentView {
    
        public void show() {
            System.out.println("Displaying Student Page");
        }
        
    }

HomeView类：前端页面二

package com.study.dp.frontcontroller;
    
    public class HomeView {
    
        public void show() {
            System.out.println("Displaying Home Page");
        }
        
    }

Dispatcher类：分发器，根据不同的请求展示不同的页面

package com.study.dp.frontcontroller;
    
    public class Dispatcher {
        
        private StudentView studentPage;
        private HomeView homePage;
        
        public Dispatcher() {
            studentPage = new StudentView();
            homePage = new HomeView();
        }
        
        public void dispatch(String request) {
            if(request.equalsIgnoreCase("STUDENT")) {
                studentPage.show();
            }else {
                homePage.show();
            }
        }
    
    }

FrontController类：前端控制器，响应用户请求

package com.study.dp.frontcontroller;
    
    public class FrontController {
    
        private Dispatcher dispatcher;
        
        public FrontController() {
            dispatcher = new Dispatcher();
        }
        
        private boolean isAuthenticUser() {
            System.out.println("User is authenticated successfully.");
            return true;
        }
        
        private void trackRequest(String request) {
            System.out.println("Page requested: "+request);
        }
        
        public void dispatchRequest(String request) {
            // 记录每一个请求
            trackRequest(request);
            // 对用户进行身份验证
            if(isAuthenticUser()) {
                dispatcher.dispatch(request);
            }
        }
        
    }

Demo类：测试类

package com.study.dp.frontcontroller;
    
    public class Demo {
    
        public static void main(String[] args) {
            FrontController frontController = new FrontController();
            frontController.dispatchRequest("HOME");
            frontController.dispatchRequest("STUDENT");
        }
        
    }

# 四、应用场景 #

[Center]: /images/20220609/cc27598df61c4449970e33fb4e991e22.png