设计模式 - 拦截过滤器模式

概述

拦截过滤器设计模式用于在应用程序的请求或响应上进行一些预处理/后处理。过滤器在将请求传递给实际的目标应用程序之前被定义并应用。过滤器可以执行身份验证/授权/日志记录或请求跟踪，然后将请求传递给相应的处理程序。以下是此类设计模式中的实体。

• Filter - 在请求处理程序执行请求之前或之后执行特定任务的过滤器。

• Filter Chain - 过滤器链携带多个过滤器，并帮助按照定义的顺序在目标上执行它们。

• Target - 目标对象是请求处理程序。

• Filter Manager - 过滤器管理器管理过滤器和过滤器链。

• Client - 客户端是向目标对象发送请求的对象。

实现

我们将创建 FilterChain、FilterManager、Target、Client 等各种对象来表示我们的实体。AuthenticationFilter 和 DebugFilter 表示具体的过滤器。

InterceptingFilterDemo，我们的演示类，将使用 Client 来演示拦截过滤器设计模式。

步骤 1

创建 Filter 接口。

Filter.java

package com.;

public interface Filter {
   public void execute(String request);
}

步骤 2

创建具体的过滤器。

AuthenticationFilter.java

package com.;

public class AuthenticationFilter implements Filter {
   public void execute(String request){
      System.out.println("Authenticating request: " + request);
   }
}

DebugFilter.java

package com.;

public class DebugFilter implements Filter {
   public void execute(String request){
      System.out.println("request log: " + request);
   }
}

步骤 3

创建 Target

Target.java

package com.;

public class Target {
   public void execute(String request){
      System.out.println("Executing request: " + request);
   }
}

步骤 4

创建 Filter Chain

FilterChain.java

package com.;

import java.util.ArrayList;
import java.util.List;

public class FilterChain {
   private List<Filter> filters = new ArrayList<Filter>();
   private Target target;

   public void addFilter(Filter filter){
      filters.add(filter);
   }

   public void execute(String request){
      for (Filter filter : filters) {
         filter.execute(request);
      }
      target.execute(request);
   }

   public void setTarget(Target target){
      this.target = target;
   }
}

步骤 5

创建 Filter Manager

FilterManager.java

package com.;

public class FilterManager {
   FilterChain filterChain;

   public FilterManager(Target target){
      filterChain = new FilterChain();
      filterChain.setTarget(target);
   }
   public void setFilter(Filter filter){
      filterChain.addFilter(filter);
   }

   public void filterRequest(String request){
      filterChain.execute(request);
   }
}

步骤 6

创建 Client

Client.java

package com.;

public class Client {
   FilterManager filterManager;

   public void setFilterManager(FilterManager filterManager){
      this.filterManager = filterManager;
   }

   public void sendRequest(String request){
      filterManager.filterRequest(request);
   }
}

示例 - 拦截过滤器模式的使用

使用 Client 来演示 Intercepting Filter Design Pattern。

InterceptingFilterPatternDemo.java

package com.;

import java.util.ArrayList;
import java.util.List;

public class InterceptingFilterPatternDemo {
   public static void main(String[] args) {
      FilterManager filterManager = new FilterManager(new Target());
      filterManager.setFilter(new AuthenticationFilter());
      filterManager.setFilter(new DebugFilter());

      Client client = new Client();
      client.setFilterManager(filterManager);
      client.sendRequest("HOME");
   }
}
interface Filter {
   public void execute(String request);
}
class AuthenticationFilter implements Filter {
   public void execute(String request){
      System.out.println("Authenticating request: " + request);  // 认证请求： + request
   }
}
class DebugFilter implements Filter {
   public void execute(String request){
      System.out.println("request log: " + request);  // 请求日志： + request
   }
}
class Target {
   public void execute(String request){
      System.out.println("Executing request: " + request);  // 执行请求： + request
   }
}
class FilterChain {
   private List<Filter> filters = new ArrayList<Filter>();
   private Target target;

   public void addFilter(Filter filter){
      filters.add(filter);
   }

   public void execute(String request){
      for (Filter filter : filters) {
         filter.execute(request);
      }
      target.execute(request);
   }

   public void setTarget(Target target){
      this.target = target;
   }
}
class FilterManager {
   FilterChain filterChain;

   public FilterManager(Target target){
      filterChain = new FilterChain();
      filterChain.setTarget(target);
   }
   public void setFilter(Filter filter){
      filterChain.addFilter(filter);
   }

   public void filterRequest(String request){
      filterChain.execute(request);
   }
}
class Client {
   FilterManager filterManager;

   public void setFilterManager(FilterManager filterManager){
      this.filterManager = filterManager;
   }

   public void sendRequest(String request){
      filterManager.filterRequest(request);
   }
}

输出

验证输出结果。

Authenticating request: HOME
request log: HOME
Executing request: HOME