第2章 servlet开发技术
Servlet是什么
servlet是基于java语言的web服务器端编程技术。按照一定规则定义的java类。他有约定好的一些方法。get post init destroy
servlet作用
无论是get/post方法都至少有两个参数，一个叫HttpServletRequest(请求对象),一个叫HttpServletResponse（响应对象）
他对外暴露一个地址，可以用于页面访问的。
servlet如何创建和定义
有两种创建方式servlet2.5以前半自动创建 （.java+web.xml）
servlet2.5注解方式创建 （
.java+注解）
第一种方式：servlet2.5以前是手动创建
1)写一个servlet类（java）继承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里配置对外暴露的地址。
web.xml在WebContent\WEB-INF\web.xml
servlet3.0自动创建
包名-new -servlet-输入servlet文件名称-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被调用");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生命周期关键方法
init()初始化方法
service()服务方法
doGet()
doPost()
......根据method不同，service将请求分发到不同方法
destory()销毁方法
注意：init()和destory()方法整个生命周期中只执行一次。service等方法可以执行多次
初始化带参数以及init里获取参数
@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被调用");//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);}
}
注册程序
新建包 com.neuedu.service com.neuedu.service.impl com.neuedu.dao
com.neuedu.dao.impl
目录结构如图
image.png
密码：
爱好：
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方法被调用");//获取前台输入的信息Stringname=request.getParameter("username");Stringpassword=request.getParameter("password");//checkbox数据String[]hobbys=request.getParameterValues("hobby");//打包userUseruser=newUser();user.setUserName(name);......//调用service进行处理IUserServiceuserService=newUserServiceImpl();inti=userService.addUser(user);//返回处理结果response.setContentType("text/html;charset=utf-8");PrintWriterout=response.getWriter();if(i>0){out.println("success");}else{out.println("failure");}}}
解决中文乱码问题
request.setCharacterEncoding("utf-8");response.setCharacterEncoding("utf-8");response.setContentType("text/html;charset=UTF-8");
request里能获取什么
应用程序上下文 request.getContextPath()
客户端ip request.getRemoteAddr()
客户端端口 request.getRemotePort()
本地地址 request.getLocalAddr()
相对路径 request.getRequestURI()
请求方式 request.getMethod()
头信息（了解，是枚举类型）
request.getHeaderNames()
//上下文路径System.out.println("应用程序上下文"+request.getContextPath());System.out.println("客户端ip"+request.getRemoteAddr());System.out.println("端口"+request.getRemotePort());System.out.println("本地addr"+request.getLocalAddr());System.out.println("相对路径"+request.getRequestURI());System.out.println("请求方式"+request.getMethod());//以下了解System.out.println(request.getHeaderNames());Enumeration
打印结果：
应用程序上下文/myproject客户端ip0:0:0:0:0:0:0:1端口51784本地addr0:0:0:0:0:0:0:1相对路径/myproject/loginServlet请求方式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
转发和重定向
转发：只发一次请求 地址栏的地址不变 只能转发到内部地址 效率高 request转发 request可以带参数
重定向：两次请求 地址栏地址会变化 可以请求外部地址 效率低 responset重定向 只能在url地址里带参数（如果重定向到的页是用html的IFRAME开发的，只能用redirect）
应用技巧：
如果请求外部地址或者跳转时不需要携带原始请求用重定向。否则用转发
重定向时加上上下文路径
response.sendRedirect(request.getContextPath()+"/user/index.html");
转发写法
request.getRequestDispatcher("/login.html").forward(request, response);
代码详见第2章代码样例（注册登录）
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java web
作者：wqjcarnation
链接：https://www.jianshu.com/p/6742b3dfee7e
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