设计模式（一）Chain Of Responsibility责任链模式

设计模式篇章，源于网课的学习，以及个人的整理

在我们接收用户提交的字符时，常常会使用到过滤，在学习责任链模式前，我们是这样做的

1.定义一个类

public class MsgProcesser {String msg;public MsgProcesser(String msg) {this.msg=msg;}public String getMsg() {return msg;}public void setMsg(String msg) {this.msg = msg;}public String process() {String r=msg.replace("<", "[").replaceAll(">", "]");r=r.replaceAll("被就业", "就业");r=r.replaceAll("敏感", "");return r;}
}

测试

public static void main(String[] args) {String message="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";MsgProcesser mp=new MsgProcesser(message);System.out.println(mp.process());}

往往添加数据会很不方便，于是，借用责任链的方式，我们可以这样写

1.定义一个接口，内部有抽象方法doFilter

package com.littlepage.testChainOfResponsibility;public interface Filter {String doFilter(String str);
}

2.定义一些不同的过滤器类实现过滤器接口，类似HTMLFilter，SensitiveFilter

package com.littlepage.testChainOfResponsibility;public class HTMLFilter implements Filter{@Overridepublic String doFilter(String str) {return str.replaceAll("<", "[").replaceAll(">", "]");    }}

package com.littlepage.testChainOfResponsibility;public class SensitiveFilter implements Filter{@Overridepublic String doFilter(String str) {return str.replaceAll("敏感", "*");}}

3.进行主要链条的编写，就是新建一个类叫MsgProcesser，该类将这些方法进行串起来，使用foreach循环进行迭代进行过滤，在后续情况下，也就是说，你需要再添加过滤的关键字，就可以直接新建一个链条上的小块（也就是一个类），进行添加，而不用再去写其他东西

package com.littlepage.testChainOfResponsibility;public class MsgProcesser {Filter[] filter= {new HTMLFilter(),new SensitiveFilter()};String msg;public MsgProcesser(String msg) {this.msg=msg;}public String getMsg() {return msg;}public void setMsg(String msg) {this.msg = msg;}public String process() {String r=msg;for(Filter f:filter) {r=f.doFilter(r);}return r;}
}

图示：

或者说，你依然可以定义一个责任链类（FilterChain）用来代替MsgProcesser类，里面用ArrayList容器盛放filter

该代码为：

package com.littlepage.testChainOfResponsibility;import java.util.ArrayList;
import java.util.List;public class FilterChain {List<Filter> filters=new ArrayList<>();public FilterChain addFilter(Filter f) {filters.add(f);return this;}public String doFilter(String str) {String r=str;for (Filter filter : filters) {r=filter.doFilter(r);}return r;}
}

主方法的调用改为

package com.littlepage.testChainOfResponsibility;public class Main {public static void main(String[] args) {String message="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";FilterChain fc=new FilterChain();fc.addFilter(new HTMLFilter()).addFilter(new SensitiveFilter());System.out.println(fc.doFilter(message));}
}

若该FilterChain也实现Filter接口，那么就可以自己添加自己的FilterChain了，很巧妙

由此可以拓展出，tomcat下可以加上request和response过滤器

代码如下：

package top.littlepage.designPattern.responsibilityChain;public interface Filter {void doFilter(Request req,Response res,FilterChain fc);
}

package top.littlepage.designPattern.responsibilityChain;import java.util.ArrayList;
import java.util.List;public class FilterChain implements Filter {List<Filter> filters = new ArrayList<>();int index = -1;public FilterChain addFilter(Filter f) {filters.add(f);return this;}public void doFilter(Request req, Response res, FilterChain fc) {if (index == filters.size()-1)return;index++;filters.get(index).doFilter(req, res, fc);}}

package top.littlepage.designPattern.responsibilityChain;public class HTTPFilter implements Filter{@Overridepublic void doFilter(Request req, Response res,FilterChain fc) {req.setRequestStr(req.getRequestStr().replaceAll("<", "[").replaceAll(">", "]"));System.out.println("after reqHttp:"+req);fc.doFilter(req, res, fc);res.setResponseStr(res.getResponseStr().replaceAll("//", "pp"));System.out.println("after resHttp:"+res);}}

package top.littlepage.designPattern.responsibilityChain;public class Request {private String requestStr;public Request() {requestStr="";}public Request(String requestStr) {this.requestStr = requestStr;}public String getRequestStr() {return requestStr;}public void setRequestStr(String requestStr) {this.requestStr = requestStr;}@Overridepublic String toString() {return "Request [requestStr=" + requestStr + "]";}
}

package top.littlepage.designPattern.responsibilityChain;public class Response {private String responseStr;public Response() {responseStr="";}public Response(String responseStr) {this.responseStr = responseStr;}public String getResponseStr() {return responseStr;}public void setResponseStr(String responseStr) {this.responseStr = responseStr;}@Overridepublic String toString() {return "Response [responseStr=" + responseStr + "]";}}

package top.littlepage.designPattern.responsibilityChain;public class SensitiveFilter implements Filter{@Overridepublic void doFilter(Request req, Response res,FilterChain fc) {req.setRequestStr(req.getRequestStr().replaceAll("sensitive", "***"));System.out.println("after reqSen:"+req);fc.doFilter(req, res, fc);res.setResponseStr(res.getResponseStr().replaceAll("mingan", "notmingan"));System.out.println("after resSen:"+res);}
}

package top.littlepage.designPattern.responsibilityChain;public class Test {public static void main(String[] args) {String str="<script>//abbbmingansensitive";Request req=new Request(str);Response res=new Response(str);FilterChain fc=new FilterChain();fc.addFilter(new HTTPFilter());fc.addFilter(new SensitiveFilter());fc.doFilter(req, res, fc);}
}