Java web系列三--简单的网页注册登录

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1.写网页有html,jsp，servlet.但是三者有各自的优缺点，html适合写一些静态的显示，jsp适合写动态可变的显示，servlet适合处理业务逻辑，分发转向，DAO数据中转。

2.本项目使用jsp+servlet来实现一个简单的网页注册和登录，需要一点jsp的语法基础，比如<% 插入java代码%>、<a herf=""></a>表示转发。form跟html一样表示表单。表示注释。
<%! %>申明全局变量等基础的语法，还有几个指令page include taglib

3.建立一个web网页，默认生成一个web.xml文件。工程名为webServletTest 在java Resouces目录下建立一个webservlet.java。

package webJspDemo.com;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * Servlet implementation class LoginServlet */@WebServlet("/servlet/loginservlet")public class LoginServlet extends HttpServlet {    private static final long serialVersionUID = 1L;    /**     * @see HttpServlet#HttpServlet()     */    public LoginServlet() {        super();        // TODO Auto-generated constructor stub    }    /**     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)     */    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        // TODO Auto-generated method stub        response.getWriter().append("Served at: ").append(request.getContextPath());        //获取表单数据        response.setContentType("text/html; charset=UTF-8");        request.setCharacterEncoding("UTF-8");        String userName = request.getParameter("userName");        String pwd = request.getParameter("pwd");        if("tom".equals(userName)&&"123".equals(pwd)){            request.getSession().setAttribute("name", userName);            request.getRequestDispatcher("/register.jsp").forward(request, response);        }else{            request.setAttribute("msg", "用户名或者密码不正确");            request.getRequestDispatcher("/login.jsp").forward(request, response);        }        //分发转向    }    /**     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)     */    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        // TODO Auto-generated method stub        doGet(request, response);    }}

4.修改web.xml的映射关系和类名

  <servlet>    <servlet-name>LoginServlet</servlet-name>    <servlet-class>webJspDemo.com.LoginServlet</servlet-class>  </servlet>  <servlet-mapping>    <servlet-name>LoginServlet</servlet-name>    <url-pattern>/login</url-pattern>  </servlet-mapping>

5.在WEB-INF目录下建立3个jsp，分别为home.jsp、login.jsp、register.jsp文件。

home.jsp代码为

<body>    <h1>欢迎来到本站!</h1>    <%        String userName =(String)session.getAttribute("name");    out.print(userName);    %></body>

<body>    <%        String msg = (String)request.getAttribute("msg");      if(msg !=null){          out.print(msg);           }    %>    <form action="/webJspDemo1/servlet/loginservlet" method="get">        用户名：<input type="text" name="userName"/><br/>        密码：<input type="password" name="pwd"/><br/>        <input type="submit" value="登录"/><br/>    </form></body>

<body>    欢迎你登录:    <%         String userName =(String)session.getAttribute("name");        out.print(userName);            %>    <a href="/webJspDemo1/home.jsp">跳到主页 </a></body>

5.实验结果
在浏览器中输入：http://localhost:8080/webJspDemo1/login
在表单中输入tom和123之后就会跳转到register.jsp界面，然后在到home.jsp界面，基本上就完成一个简单的注册流程。

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