設計模式篇章，源于網課的學習，以及個人的整理

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在我們接收用戶提交的字符時，常常會使用到過濾，在學習責任鏈模式前，我們是這樣做的

1.定義一個類

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("被就業", "就業");r=r.replaceAll("敏感", "");return r;} }

測試

public static void main(String[] args) {String message="大家好:),<script>,敏感,被就業,網絡授課沒感覺,因為看不見大家伙兒";MsgProcesser mp=new MsgProcesser(message);System.out.println(mp.process());}

往往添加數據會很不方便，于是，借用責任鏈的方式，我們可以這樣寫

?1.定義一個接口，內部有抽象方法doFilter

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

2.定義一些不同的過濾器類實現過濾器接口，類似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.進行主要鏈條的編寫，就是新建一個類叫MsgProcesser，該類將這些方法進行串起來，使用foreach循環進行迭代進行過濾，在后續情況下，也就是說，你需要再添加過濾的關鍵字，就可以直接新建一個鏈條上的小塊（也就是一個類），進行添加，而不用再去寫其他東西

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;} }

圖示：

或者說，你依然可以定義一個責任鏈類（FilterChain）用來代替MsgProcesser類，里面用ArrayList容器盛放filter

該代碼為：

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;} }

主方法的調用改為

package com.littlepage.testChainOfResponsibility;public class Main {public static void main(String[] args) {String message="大家好:),<script>,敏感,被就業,網絡授課沒感覺,因為看不見大家伙兒";FilterChain fc=new FilterChain();fc.addFilter(new HTMLFilter()).addFilter(new SensitiveFilter());System.out.println(fc.doFilter(message));} }

若該FilterChain也實現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過濾器

代碼如下：

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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);} }

控制臺打印如下

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可以看出，首先接收端進行接收request分別執行Http進行過濾req，執行Sensitive進行過濾req

到達服務端，開始原路返回，先執行Sensitive過濾器進行過濾，然后執行Http過濾器進行過濾，

這一系列變成了一個鏈條，將各個過濾器穿在一起，也就成了所說的責任鏈設計模式。

由于是一步一步進行攔截，所以說，也可以稱作攔截器模式

由此可見：原理和tomcat的filter的大致原理一樣，先原線路進行依次對請求值進行過濾，然后

再對客戶端的返回值進行過濾

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轉載于:https://www.cnblogs.com/littlepage/p/9914497.html

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