设计模式学习—拦截过滤器模式(Intercepting Filter Design Pattern)

旧城等待， 2022-06-07 22:27 104阅读 0赞

# 一、我的理解 #

这个模式感觉跟Servlet中的过滤器类似，它让请求在被处理前可以先被定义好的过滤器使用并处理，有点类似AOP编程的意思。

# 二、实现方式 #

定义一个过滤器链和一个过滤器管理类，当请求到达时，先传递给管理类，管理类调用过滤器链过滤请求，并依次向下传递请求，当执行完最后一个过滤器时，再交给请求的目标处理类处理。

# 三、实例 #

![Center][]

###### Java实例 ######

Filter接口：定义过滤器统一对外处理的接口函数

package com.study.dp.interceptingfilter;
    
    public interface Filter {
    
        public void execute(String request);
        
    }

AuthenticationFilter类：实际的过滤器之一

package com.study.dp.interceptingfilter;
    
    public class AuthenticationFilter implements Filter {
    
        @Override
        public void execute(String request) {
            System.out.println("Authenticating request: "+request);
        }
    
    }

DebugFilter类：实际的过滤器之二

package com.study.dp.interceptingfilter;
    
    public class DebugFilter implements Filter {
    
        @Override
        public void execute(String request) {
            System.out.println("Request log: "+request);
        }
    
    }

FilterChain类：过滤器链

package com.study.dp.interceptingfilter;
    
    import java.util.ArrayList;
    import java.util.List;
    
    public class FilterChain {
    
        private List<Filter> filters = new ArrayList<>();
        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;
        }
        
    }

FilterManager类：过滤器管理类

package com.study.dp.interceptingfilter;
    
    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);
        }
    }

Target类：请求的实际处理类

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

Client类：客户端程序

package com.study.dp.interceptingfilter;
    
    public class Client {
    
        FilterManager filterManager;
    
        public void setFilterManager(FilterManager filterManager) {
            this.filterManager = filterManager;
        }
        
        public void sendRequest(String request) {
            filterManager.filterRequest(request);
        }
        
    }

Demo类：测试程序

package com.study.dp.interceptingfilter;
    
    public class Demo {
        
        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");
        }
    
    }

# 四、应用场景 #

[Center]: /images/20220608/45c37c6dd0f34c8cb109829992ab47c9.png