第2章 servlet開發(fā)技術
Servlet是什么
servlet是基于java語言的web服務器端編程技術。按照一定規(guī)則定義的java類。他有約定好的一些方法。get post init destroy
servlet作用
無論是get/post方法都至少有兩個參數(shù)，一個叫HttpServletRequest(請求對象),一個叫HttpServletResponse（響應對象）
他對外暴露一個地址，可以用于頁面訪問的。
servlet如何創(chuàng)建和定義
有兩種創(chuàng)建方式servlet2.5以前半自動創(chuàng)建 （.java+web.xml）
servlet2.5注解方式創(chuàng)建? （
.java+注解）
第一種方式：servlet2.5以前是手動創(chuàng)建
1)寫一個servlet類（java）繼承HttpServlet
publicclassTestServletextendsHttpServlet{@OverrideprotectedvoiddoGet(HttpServletRequestreq,HttpServletResponseresp)throwsServletException,IOException{// TODO Auto-generated method stubsuper.doGet(req,resp);}@OverrideprotectedvoiddoPost(HttpServletRequestreq,HttpServletResponseresp)throwsServletException,IOException{// TODO Auto-generated method stubsuper.doPost(req,resp);}}
2）web.xml里配置對外暴露的地址。
web.xml在WebContent\WEB-INF\web.xml
<servlet><servlet-name>TestServlet</servlet-name><servlet-class>com.neuedu.javaweb.chap02.TestServlet</servlet-class></servlet><servlet-mapping><servlet-name>TestServlet</servlet-name><url-pattern>/test.do</url-pattern></servlet-mapping>
servlet3.0自動創(chuàng)建
包名-new -servlet-輸入servlet文件名稱-下一步-urlmapping里可以更改映射地址-finish
@WebServlet("/regServlet")publicclassRegServletextendsHttpServlet{privatestaticfinallongserialVersionUID=1L;/**
* @see HttpServlet#HttpServlet()
*/publicRegServlet(){super();// TODO Auto-generated constructor stub}/**
? ? * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
? ? */protectedvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{// TODO Auto-generated method stubSystem.out.println("doGet被調(diào)用");response.getWriter().append("Served at: ").append(request.getContextPath());}/**
? ? * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
? ? */protectedvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{// TODO Auto-generated method stubdoGet(request,response);}}
servlet生命周期關鍵方法
init()初始化方法
service()服務方法
doGet()
doPost()
......根據(jù)method不同，service將請求分發(fā)到不同方法
destory()銷毀方法
注意：init()和destory()方法整個生命周期中只執(zhí)行一次。service等方法可以執(zhí)行多次
初始化帶參數(shù)以及init里獲取參數(shù)
@WebServlet(value="/regServlet",initParams={@WebInitParam(name="driver",value="com.mysql.jdbc.Driver"),@WebInitParam(name="userName",value="root"),@WebInitParam(name="passWord",value="root")})publicclassRegServletextendsHttpServlet{privatestaticfinallongserialVersionUID=1L;/**
* @see HttpServlet#HttpServlet()
*/publicRegServlet(){super();// TODO Auto-generated constructor stub}@Overridepublicvoidinit(ServletConfigconfig)throwsServletException{// TODO Auto-generated method stubSystem.out.println(config.getInitParameter("userName"));super.init(config);}/**
? ? * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/protectedvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{// TODO Auto-generated method stubSystem.out.println("doGet被調(diào)用");//response.getWriter().append("Served at: ").append(request.getContextPath());PrintWriterout=response.getWriter();out.println("success");}/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/protectedvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{// TODO Auto-generated method stubdoGet(request,response);}
}
注冊程序
新建包 com.neuedu.service com.neuedu.service.impl? com.neuedu.dao
com.neuedu.dao.impl
目錄結構如圖
image.png
<!DOCTYPE html><html><head><metacharset="UTF-8"><title>注冊頁面</title></head><body>注冊頁面<br><formaction="regServlet"method="post">賬號：<inputtype="text"name="username"/><br>密碼：<inputtype="password"name="password"/><br>愛好：<inputtype="checkbox"name="hobby"value="1">打籃球<inputtype="checkbox"name="hobby"value="2">踢足球<inputtype="checkbox"name="hobby"value="3">燙頭<inputtype="submit"value="注冊"/></form></body></html>
servlet
packagecom.neuedu.javaweb.chap02;importjava.io.IOException;importjava.io.PrintWriter;importjavax.servlet.ServletConfig;importjavax.servlet.ServletException;importjavax.servlet.annotation.WebInitParam;importjavax.servlet.annotation.WebServlet;importjavax.servlet.http.HttpServlet;importjavax.servlet.http.HttpServletRequest;importjavax.servlet.http.HttpServletResponse;/**
* Servlet implementation class RegServlet
*/@WebServlet(value="/regServlet",initParams={@WebInitParam(name="driver",value="com.mysql.jdbc.Driver"),@WebInitParam(name="userName",value="root"),@WebInitParam(name="passWord",value="root")})publicclassRegTestServletextendsHttpServlet{privatestaticfinallongserialVersionUID=1L;/**
* @see HttpServlet#HttpServlet()
*/publicRegTestServlet(){super();// TODO Auto-generated constructor stub}@Overridepublicvoidinit(ServletConfigconfig)throwsServletException{// TODO Auto-generated method stubSystem.out.println(config.getInitParameter("userName"));super.init(config);}/**
? ? * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
? ? */protectedvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{doPost(request,response);}/**
? ? * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
? ? */protectedvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{System.out.println("doPost方法被調(diào)用");//獲取前臺輸入的信息Stringname=request.getParameter("username");Stringpassword=request.getParameter("password");//checkbox數(shù)據(jù)String[]hobbys=request.getParameterValues("hobby");//打包userUseruser=newUser();user.setUserName(name);......//調(diào)用service進行處理IUserServiceuserService=newUserServiceImpl();inti=userService.addUser(user);//返回處理結果response.setContentType("text/html;charset=utf-8");PrintWriterout=response.getWriter();if(i>0){out.println("success");}else{out.println("failure");}}}
解決中文亂碼問題
request.setCharacterEncoding("utf-8");response.setCharacterEncoding("utf-8");response.setContentType("text/html;charset=UTF-8");
request里能獲取什么
應用程序上下文 request.getContextPath()
客戶端ip? ? ? request.getRemoteAddr()
客戶端端口? ? request.getRemotePort()
本地地址? ? ? request.getLocalAddr()
相對路徑? ? ? request.getRequestURI()
請求方式? ? ? request.getMethod()
頭信息（了解，是枚舉類型）
request.getHeaderNames()
//上下文路徑System.out.println("應用程序上下文"+request.getContextPath());System.out.println("客戶端ip"+request.getRemoteAddr());System.out.println("端口"+request.getRemotePort());System.out.println("本地addr"+request.getLocalAddr());System.out.println("相對路徑"+request.getRequestURI());System.out.println("請求方式"+request.getMethod());//以下了解System.out.println(request.getHeaderNames());Enumeration<String>headers=request.getHeaderNames();while(headers.hasMoreElements()){Stringkey=headers.nextElement();Stringvalue=request.getHeader(key);System.out.println("key--->"+key);System.out.println("value--->"+value);}
打印結果：
應用程序上下文/myproject客戶端ip0:0:0:0:0:0:0:1端口51784本地addr0:0:0:0:0:0:0:1相對路徑/myproject/loginServlet請求方式POSTorg.apache.tomcat.util.http.NamesEnumerator@3c32a826key---->hostvalue-->localhost:8081key---->connectionvalue-->keep-alivekey---->content-lengthvalue-->31key---->cache-controlvalue-->max-age=0key---->originvalue-->http://localhost:8081key---->upgrade-insecure-requestsvalue-->1key---->content-typevalue-->application/x-www-form-urlencodedkey---->user-agentvalue-->Mozilla/5.0(Windows NT6.1;WOW64)AppleWebKit/537.36(KHTML,like Gecko)Chrome/70.0.3538.16Safari/537.36key---->acceptvalue-->text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8key---->referervalue-->http://localhost:8081/myproject/login.htmlkey---->accept-encodingvalue-->gzip,deflate,brkey---->accept-languagevalue-->zh-CN,zh;q=0.9key---->cookievalue-->Webstorm-a327319a=cc9d0535-8c62-45c6-91d2-ba803bc9a72d
轉發(fā)和重定向
轉發(fā)：只發(fā)一次請求? 地址欄的地址不變 只能轉發(fā)到內(nèi)部地址? 效率高? request轉發(fā)? ? request可以帶參數(shù)
重定向：兩次請求? ? 地址欄地址會變化 可以請求外部地址? ? 效率低? responset重定向? 只能在url地址里帶參數(shù)（如果重定向到的頁是用html的IFRAME開發(fā)的，只能用redirect）
應用技巧：
如果請求外部地址或者跳轉時不需要攜帶原始請求用重定向。否則用轉發(fā)
重定向時加上上下文路徑
response.sendRedirect(request.getContextPath()+"/user/index.html");
轉發(fā)寫法
request.getRequestDispatcher("/login.html").forward(request, response);
代碼詳見第2章代碼樣例（注冊登錄）
2人點贊
作者：wqjcarnation
鏈接：http://www.itdecent.cn/p/6742b3dfee7e
來源：簡書
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