設計模式—責任鏈模式，設計模式責任

設計模式—責任鏈模式，設計模式責任

責任鏈將處理請求在鏈條的節點上傳遞，每到一個節點可被處理或者也可不被處理。

典型的是在servlet中過濾器filter的的處理方式。當request請求或者response請求時，請求經過過濾鏈上的節點後，又進入下一個節點，直到鏈尾。

下面以模仿servlet中filter的處理方式（馬士兵老師設計模式講解內容）：

1.過濾器介面

package com.bjsxt.dp.filter;public interface Filter {    void doFilter(Request request, Response response, FilterChain chain);}

2.過濾器鏈

package com.bjsxt.dp.filter;import java.util.ArrayList;import java.util.List;public class FilterChain implements Filter {    List<Filter> filters = new ArrayList<Filter>();    int index = 0;        public FilterChain addFilter(Filter f) {        this.filters.add(f);        return this;    }        @Override    public void doFilter(Request request, Response response, FilterChain chain) {        if(index == filters.size()) return ;                Filter f = filters.get(index);        index ++;        f.doFilter(request, response, chain);    }}

3.過濾鏈_1

package com.bjsxt.dp.filter;public class HTMLFilter implements Filter {      @Override    public void doFilter(Request request, Response response, FilterChain chain) {        //process the html tag <>        request.requestStr = request.requestStr.replace('<', '[')                   .replace('>', ']') + "---HTMLFilter()";        chain.doFilter(request, response, chain);        response.responseStr += "---HTMLFilter()";    }}

4.過濾器_2

package com.bjsxt.dp.filter;public class SesitiveFilter implements Filter {    @Override    public void doFilter(Request request, Response response, FilterChain chain) {        request.requestStr = request.requestStr.replace("被就業", "就業")         .replace("敏感", "") + "---SesitiveFilter()";        chain.doFilter(request, response, chain);        response.responseStr += "---SesitiveFilter()";        }    }

5.request請求

package com.bjsxt.dp.filter;public class Request {    String requestStr;    public String getRequestStr() {        return requestStr;    }    public void setRequestStr(String requestStr) {        this.requestStr = requestStr;    }}

6.response請求

package com.bjsxt.dp.filter;public class Response {    String responseStr;    public String getResponseStr() {        return responseStr;    }    public void setResponseStr(String responseStr) {        this.responseStr = responseStr;    }    }

7.用戶端請求

package com.bjsxt.dp.filter;public class Main {    /**     * @param args     */    public static void main(String[] args) {        String msg = "大家好:)，<script>，敏感，被就業，網路授課沒感覺，因為看不見大傢伙兒";        Request request = new Request();        request.setRequestStr(msg);        Response response = new Response();        response.setResponseStr("response");        FilterChain fc = new FilterChain();        fc.addFilter(new HTMLFilter())          .addFilter(new SesitiveFilter())          ;              fc.doFilter(request, response, fc);        System.out.println(request.getRequestStr());        System.out.println(response.getResponseStr());    }}

 FilterChain中建立了一個過濾鏈，記錄了有多少個過濾器，並且遞迴調用doFilter，經過一個過濾器後就走下一個過濾器，直到鏈尾。在遞迴返回的時候接著對response處理，處理的順序和request

的順序相反。

 

過濾鏈處理之後結果：