责任链模式(ChainOfResponsibiliby、Filter)

Request 类:

package com.demo;

public class Request {
    
    private String requestStr;

    public String getRequestStr() {
        return requestStr;
    }

    public void setRequestStr(String requestStr) {
        this.requestStr = requestStr;
    }

}

Response 类:

package com.demo;

public class Response {
    
    private String responseStr;

    public String getResponseStr() {
        return responseStr;
    }

    public void setResponseStr(String responseStr) {
        this.responseStr = responseStr;
    }
    
}

Filter 接口:

package com.demo;

public interface Filter {
    void doFilter(Request request,Response response,FilterChain chain);
}

FilterChain 类，实现Filter接口，重写doFilter()方法，用来遍历过滤器链中所有的filter:

package com.demo;

import java.util.ArrayList;

public class FilterChain implements Filter{
    
    //过滤器链
    private ArrayList<Filter> chain = new ArrayList<Filter>();
    
    //过滤器链的索引
    int index = 0;
    
    //往过滤器链中添加过滤器
    public ArrayList<Filter> add(Filter filter){
        chain.add(filter);
        return chain;
    }
    
    /**
     * 重写 doFilter方法
     * 如果没有遍历完，调用特定过滤器的doFilter方法
     */
    @Override
    public void doFilter(Request request, Response response, FilterChain chain) {
        //如果遍历完过滤器链，则返回
        if(index == this.chain.size()) return;
        
        Filter filter = this.chain.get(index);
        index ++;
        filter.doFilter(request, response, chain);
    }
    
}

HTMLFilter (Fiter接口的实现类):

package com.demo;

public class HTMLFilter implements Filter {

    @Override
    public void doFilter(Request request, Response response, FilterChain chain) {
        //处理过滤器该干的事情
        request.setRequestStr(request.getRequestStr().replace('<', '[').replace('>', ']')
                + "---HTMLFilter()");
        
        //跳往下一个过滤器
        chain.doFilter(request, response, chain);
        
        //回调
        response.setResponseStr(response.getResponseStr() + "---HTMLFilter()");
    }

}

SensitiveFilter (Fiter接口的实现类):

package com.demo;

public class SensitiveFilter implements Filter {

    @Override
    public void doFilter(Request request, Response response, FilterChain chain) {
        //处理过滤器该干的事情
        request.setRequestStr(request.getRequestStr().replace("被就业", "就业").replace("敏感", "") 
                + "---SensitiveFilter()");
        
        //跳往下一个过滤器
        chain.doFilter(request, response, chain);
        
        //回调
        response.setResponseStr(response.getResponseStr() + "---SensitiveFilter()");
    }

}

Main 执行过滤器操作的类:

package com.demo;

public class Main {
    public static void main(String[] args) {
        //请求信息
        String msg = "大家好:)，<script>，敏感，被就业，网络授课没感觉，因为看不见大家伙儿";
        
        //实例化Request对象
        Request request = new Request();
        request.setRequestStr(msg);
        
        //实例化Response对象
        Response response = new Response();
        response.setResponseStr("response");
        
        //过滤器链
        FilterChain chain = new FilterChain();
        chain.add(new HTMLFilter()).add(new SensitiveFilter());
        
        //开始过滤
        chain.doFilter(request, response, chain);
        
        //打印处理结果
        System.out.println(request.getRequestStr());
        System.out.println(response.getResponseStr());
        
    }
}

思路：

　　在操作类中调用过滤器链的doFilter方法后，开始遍历过滤器;

　　当每执行完该过滤器的操作后马上chain.doFilter()方法跳往下一个filter，

　　当然，下一个filter的操作思路也是一致的，直至所有的request做完后，过滤器链返回；

　　所有的filter 接着执行doFiter之后的response操作了，而且是逆序的。这样就实现了过滤器的顺着进来，逆着出去的操作。

　　如果不是很清楚，用debug模式进行调试，从main方法的doFilter开始。

代码：http://pan.baidu.com/s/1kUGVy2F 提取码：9q6z