java责任链模式

 Struts2的拦截器功能强大，每个Action调用之前都会进行过滤器权限的校验、文件格式的校验等，拦截器用到的主要设计模式

就是责任链模式思想了，包括Netty中的ChannelPipeline，也可以看成是一个链条容器，链条就是ChannelHandler了，
下面通过一个列子来演示责任链模式来展示其设计巧妙之处。
先定义一个接口Filter，即过滤器或者拦截器，里面有一个doFilter方法，用于过滤或拦截一些信息。

package com.sf.simba.filter;
/**
 * 
 * @author -simba-
 *
 */
public interface Filter {
      void doFilter(Request request,Response response,FilterChain filterChain);
}

   定义一个HTMLFilter专门过滤含有html语言的类

package com.sf.simba.filter;
/**
 * html语言过滤器
 * @author -simba-
 *
 */
public class HTMLFilter implements Filter {

    @Override
    public void doFilter(Request request, Response response,
            FilterChain filterChain) {
        request.setRequestStr(request.getRequestStr().replaceAll("<", "[").replaceAll(">", "]"));
        System.out.println("------request:HTMLFilter-------");
        filterChain.doFilter(request, response, filterChain);//执行下一个拦截器
        response.setResponseStr(response.getResponseStr()+"------response:HTMLFilter------");//response返回


    }

}

权限校验类

package com.sf.simba.filter;
/**
 * 权限过滤器
 * @author -simba-
 *
 */
public class PowerFilter implements Filter {

    @Override
    public void doFilter(Request request, Response response,
            FilterChain filterChain) {
        request.setRequestStr(request.getRequestStr().replaceAll("权限", "你有权限"));
        System.out.println("------request:PowerFilter-------");
        filterChain.doFilter(request, response, filterChain);
        response.setResponseStr(response.getResponseStr()+"------response:PowerFilter------");

    }

}

敏感信息过滤类

package com.sf.simba.filter;
/**
 * 敏感过滤器
 * @author -Simba-
 *
 */
public class SensitiveFilter implements Filter {

    @Override
    public void doFilter(Request request, Response response,
            FilterChain filterChain) {
        request.setRequestStr(request.getRequestStr().replaceAll("饭桶在政府", "高手在民间"));
        System.out.println("------request:SensitiveFilter-------");
        filterChain.doFilter(request, response, filterChain);
        response.setResponseStr(response.getResponseStr()+"------response:SensitiveFilter------");
    }

}

请求类

package com.sf.simba.filter;
/**
 * 请求类
 * @author -simba-
 *
 */
public class Request  {
    private String requestStr;



    public String getRequestStr() {
        return requestStr;
    }

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

}

返回类

package com.sf.simba.filter;

public class Response  {
   private String responseStr;

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

}

过滤器处理类，处理每个链，其中它自己也是一个链，只是这个链中包含了几个小链条。

package com.sf.simba.filter;

import java.util.ArrayList;
import java.util.List;
/**
 * 拦截器链本身也是一种拦截器
 * @author -simba-
 *
 */
public class FilterChain implements Filter {

    private List<Filter> filters = new ArrayList<Filter>();

    private  int index = 0;

    public FilterChain addFilter(Filter filter){
        this.filters.add(filter);
        return this;
    }
    @Override
    public void doFilter(Request request, Response response,
            FilterChain filterChain) {

        if(index >= filters.size()) return;
        Filter filter = filters.get(index);
        if(filter instanceof FilterChain){//如果拦截器是一种拦截器链，那么需要把自己传入，即一个新的拦截器链
            filter.doFilter(request, response, (FilterChain)filter);
        }
        index ++;
        filter.doFilter(request, response, filterChain);//把拦截器链传个拦截器，好让拦截器知道下一个拦截器是谁

    }

}

测试类

package com.sf.simba.filter;

public class FilterMain {

    public static void main(String[] args) {
        String message = "你知道吗？饭桶在政府，<script>alert('权限')</script>,哈哈";

        Request request = new Request();
        request.setRequestStr(message);
        Response response = new Response();
        response.setResponseStr("response:");

        FilterChain filterChain = new FilterChain();
        filterChain.addFilter(new HTMLFilter())
                   .addFilter(new PowerFilter());

        FilterChain filterChain1 = new FilterChain();
        filterChain1.addFilter(new SensitiveFilter())
                    .addFilter(filterChain);
        filterChain1.doFilter(request, response, filterChain1);
        System.out.println(request.getRequestStr());
        System.out.println(response.getResponseStr());

    }

}

测试结果

——request:SensitiveFilter——-
——request:HTMLFilter——-
——request:PowerFilter——-
你知道吗？高手在民间，[script]alert(‘你有权限’)[/script],哈哈
response:——response:PowerFilter————response:HTMLFilter————response:SensitiveFilter——

拦截器原理图如下：