ServletJsp之登录界面

来源：互联网发布：cf淘宝刷枪是真的吗编辑：程序博客网时间：2024/04/28 00:40

今天我们来做一个登陆界面，实现用户登录、注销功能。
首先我们建立一个数据库db_jsp，建一个表t_user包含用户名和密码。

create table `t_user` (    `id` int (11),    `userName` varchar (60),    `password` varchar (60)); insert into `t_user` (`id`, `userName`, `password`) values('1','root','123');

然后用eclipse建立一个动态页面工程。
首先我们写一个登录界面login.jsp。

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>登录界面</title></head><body>    <form action="login" method="post">        <table>            <tr>                <th colspan="2">用户登录</th>            </tr>            <tr>                <td>用户名</td>                <td><input type="text" id="userName" name="userName"                    value="${userName }" /></td>            </tr>            <tr>                <td>密码</td>                <td><input type="password" id="password" name="password"                    value="${password }" /></td>            </tr>            <tr>                <td><input type="submit" value="登录" /></td>                <td><font color="red">${error}</font></td>            </tr>        </table>    </form></body></html>

以及登录进去的界面main.jsp。

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body>    主页！当前登录用户:${currentUser.userName }&nbsp;&nbsp;    <a href="logout">注销</a></body></html>

然后就是后台功能的实现。
我这里将后台分为6个package，分别实现不同的功能。
model package：存放自定义类。
dao package：实现自定义类的数据库操作。
util：实现一些常用的操作，例如数据库连接。
web：实现Servlet。
filter：实现一些过滤功能。
listener：实现监听功能。

model package包含了User.java。

public class User {    private int id;    private String userName;    private String password;    //构造方法、get、set方法从略}

util package包含了DbUtil.java。

public class DbUtil {    private String url = "jdbc:mysql://localhost:3306/db_jsp?useSSL=false";    private String user = "root";    private String password = "123456";    private String jdbcName = "com.mysql.jdbc.Driver";    public Connection getConnection() throws Exception {        Class.forName(jdbcName);        Connection con = DriverManager.getConnection(url, user, password);        return con;    }    public void closeConnection(Connection con) throws Exception {        if (con != null) {            con.close();        }    }    public static void main(String[] args) throws Exception {        DbUtil dbUtil = new DbUtil();        Connection con = dbUtil.getConnection();        dbUtil.closeConnection(con);    }}

dao package包含了UserDao.java。

public class UserDao {    //实现登录功能    public User login(Connection con, User user) throws Exception {        User resultUser = null;        String sql = "select * from t_user where userName=? and password=?;";        PreparedStatement pstmt = con.prepareStatement(sql);        pstmt.setString(1, user.getUserName());        pstmt.setString(2, user.getPassword());        ResultSet rs = pstmt.executeQuery();        if (rs.next()) {            resultUser = new User();            resultUser.setUserName(rs.getString("userName"));            resultUser.setPassword(rs.getString("password"));        }        return resultUser;    }}

web package包含了LoginServlet.java以及LogoutServlet.java。

public class LoginServlet extends HttpServlet {    private static final long serialVersionUID = 1L;    DbUtil dbUtil = new DbUtil();    UserDao userDao = new UserDao();    protected void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        this.doPost(request, response);    }    protected void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        String userName = request.getParameter("userName");        String password = request.getParameter("password");        Connection con = null;        try {            User user = new User(userName, password);            con = dbUtil.getConnection();            User currentUser = userDao.login(con, user);            if (currentUser == null) {                request.setAttribute("error", "用户名或者密码错误");                request.setAttribute("userName", userName);                request.setAttribute("password", password);                request.getRequestDispatcher("login.jsp").forward(request, response); // 服务器内跳转，可以带request参数            } else {                HttpSession session = request.getSession();                session.setAttribute("currentUser", currentUser);                response.sendRedirect("main.jsp");// 客户端跳转，不可以带request参数，只能使用session参数            }        } catch (Exception e) {            e.printStackTrace();        }    }}

public class LogoutServlet extends HttpServlet {    private static final long serialVersionUID = 1L;    protected void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        this.doPost(request, response);    }    protected void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        request.getSession().invalidate();// 删除所有保存的session        response.sendRedirect("login.jsp");// 客户端跳转，回到登陆界面    }}

filter package包含了LoginFilter.java。

public class LoginFilter implements Filter {    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)            throws IOException, ServletException {        HttpServletRequest httpRequest = (HttpServletRequest) request;        HttpSession session = httpRequest.getSession();        Object o = session.getAttribute("currentUser");        String path = httpRequest.getServletPath();// 获取用户当前的路径        if (o == null && path.indexOf("login") < 0) // 如果用户不在登录界面并且当前登录用户为空        {            httpRequest.getRequestDispatcher("login.jsp").forward(request, response);// 跳转回login.jsp        } else {            chain.doFilter(request, response);// 如果已经登录，执行默认方法        }    }    public void init(FilterConfig filterConfig) throws ServletException {    }    public void destroy() {    }}

listener package包含了SessionAttribute.java。

public class SessionAttribute implements HttpSessionAttributeListener {    public void attributeAdded(HttpSessionBindingEvent httpSessionBindingEvent) {        System.out.println("添加的属性名" + httpSessionBindingEvent.getName() + ",属性值" + httpSessionBindingEvent.getValue());    }    public void attributeRemoved(HttpSessionBindingEvent httpSessionBindingEvent) {        System.out.println("删除的属性名" + httpSessionBindingEvent.getName() + ",属性值" + httpSessionBindingEvent.getValue());    }    public void attributeReplaced(HttpSessionBindingEvent httpSessionBindingEvent) {    }}

最后我们在web.xml中注册一下servlet、filter以及listener。

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    xmlns="http://java.sun.com/xml/ns/javaee"    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"    id="WebApp_ID" version="2.5">    <display-name>UserLoginJsp</display-name>    <welcome-file-list>        <welcome-file>login.jsp</welcome-file>    </welcome-file-list>    <servlet>        <description></description>        <servlet-name>LoginServlet</servlet-name>        <servlet-class>com.tth.web.LoginServlet</servlet-class>    </servlet>    <servlet-mapping>        <servlet-name>LoginServlet</servlet-name>        <url-pattern>/login</url-pattern>    </servlet-mapping>    <servlet>        <description></description>        <servlet-name>LogoutServlet</servlet-name>        <servlet-class>com.tth.web.LogoutServlet</servlet-class>    </servlet>    <servlet-mapping>        <servlet-name>LogoutServlet</servlet-name>        <url-pattern>/logout</url-pattern>    </servlet-mapping>    <filter>        <filter-name>LoginFilter</filter-name>        <filter-class>com.tth.filter.LoginFilter</filter-class>    </filter>    <filter-mapping>        <filter-name>LoginFilter</filter-name>        <url-pattern>/*</url-pattern>    </filter-mapping>    <listener>        <listener-class>com.tth.listener.SessionAttribute</listener-class>    </listener></web-app>

这样一个简单的用户登录登出就完成了！

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