Java设计模式 - 前端控制器模式前端控制器模式主要用来集中处理请求，这样所有的请求都只经过一个处理器处理。这个处理器

前端控制器模式主要用来集中处理请求，这样所有的请求都只经过一个处理器处理。这个处理器可以集中处理授权，日志，跟踪请求等。主要分为，Dispatcher，将请求分配到合适的处理器，FrontController，接受所有的请求。View 展示视图。

实现

HomeView.java

public class HomeView {
   public void show(){
      System.out.println("Displaying Home Page");
   }
}

StudentView.java

public class StudentView {
   public void show(){
      System.out.println("Displaying Student Page");
   }
}

Dispatcher.java

public class Dispatcher {
   private StudentView studentView;
   private HomeView homeView;
   
   public Dispatcher(){
      studentView = new StudentView();
      homeView = new HomeView();
   }

   public void dispatch(String request){
      if(request.equalsIgnoreCase("STUDENT")){
         studentView.show();
      }
      else{
         homeView.show();
      }	
   }
}

FrontController.java

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){
      //log each request
      trackRequest(request);
      
      //authenticate the user
      if(isAuthenticUser()){
         dispatcher.dispatch(request);
      }	
   }
}

FrontControllerPatternDemo.java

public class FrontControllerPatternDemo {
   public static void main(String[] args) {
   
      FrontController frontController = new FrontController();
      frontController.dispatchRequest("HOME");
      frontController.dispatchRequest("STUDENT");
   }
}

输出：

Page requested: HOME
User is authenticated successfully.
Displaying Home Page
Page requested: STUDENT
User is authenticated successfully.
Displaying Student Page