JavaEE_JavaScript__前台(Jsp页面) + 后台数据处理(Servlet),与javaScript的过程的处理
2015-11-18 15:37
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今天一直遇到一个问题,JSP利用JavaScript 函数将密码进行了清空,后台查看数据的时候,没有找到数据。
分析后的原因为:JavaScript 的代码执行的过程为提交表单之前,因为 javaScript的代码执行修改了表单数据,导致后台接收不到数据,代码如下:
后台Servlet 代码:
DAO代码
分析后的原因为:JavaScript 的代码执行的过程为提交表单之前,因为 javaScript的代码执行修改了表单数据,导致后台接收不到数据,代码如下:
<%-- version 1.0 Copyright (C), 2001-2016, yeeku.H.Lee This program is protected by copyright laws. Program Name: Date: --%> <%@ page contentType="text/html; charset=GBK" language="java" errorPage="" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title> 用户登录 </title> <meta name="website" content="http://www.crazyit.org" /> </head> <body> <!-- 输出出错提示 --> <span style="color:red;font-weight:bold"> <% if (request.getAttribute("err") != null) { out.println(request.getAttribute("err") + "<br/>"); } %> </span> 请输入用户名和密码: <!-- 登录表单,该表单提交到一个Servlet --> <form id="login" method="post" action="login"> 用户名:<input type="text" name="username"/><br/> 密 码:<input type="password" id="pass" name="pass"/><br/> <input type="submit" value="登录" id="submitk"/><br/> </form> <script type="text/javascript"> /* var clear = function(){ if(document.getElementById("pass").value != null){ //alert("清空密码"); document.getElementById("pass").value = ""; } } document.getElementById("submitk").onclick = clear; */ </script> </body> </html>
后台Servlet 代码:
package lee; import java.io.IOException; import java.sql.ResultSet; import javax.servlet.RequestDispatcher; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; /** * Description: <br/> * 网站: <a href="http://www.crazyit.org">疯狂Java联盟</a> <br/> * Copyright (C), 2001-2016, Yeeku.H.Lee <br/> * This program is protected by copyright laws. <br/> * Program Name: <br/> * Date: * * @author Yeeku.H.Lee kongyeeku@163.com * @version 1.0 */ // @WebServlet(name = "login", urlPatterns = { "/login" }) public class LoginServlet extends HttpServlet { // 响应客户端请求的方法 public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, java.io.IOException { String errMsg = ""; // Servlet本身并不输出响应到客户端,因此必须将请求转发到视图页面 RequestDispatcher rd; // 获取请求参数 String username = request.getParameter("username"); String pass = request.getParameter("pass"); System.out.println("前台传递的密码:" + pass); try { // Servlet本身并不执行任何的业务逻辑处理,它调用JavaBean处理用户请求 DbDao dd = new DbDao("com.mysql.jdbc.Driver", "jdbc:mysql://localhost:3306/liuyan", "root", "123456"); // 查询结果集 ResultSet rs = dd.query("select pass from user_inf" + " where name = ?", username); if (rs.next()) { // 用户名和密码匹配 System.out.println("数据库中的密码:" + rs.getString("pass")); // System.out.println(username + "---ssss"); // System.out.println(pass + "---ssss"); if (rs.getString("pass").equals(pass)) { // 获取session对象 HttpSession session = request.getSession(true); // 设置session属性,跟踪用户会话状态 session.setAttribute("name", username); // 获取转发对象 rd = request.getRequestDispatcher("/welcome.jsp"); // 转发请求 rd.forward(request, response); } else { // 用户名和密码不匹配时 errMsg += "您的用户名密码不符合,请重新输入"; } } else { // 用户名不存在时 errMsg += "您的用户名不存在,请先注册"; } } catch (Exception e) { e.printStackTrace(); } // 如果出错,转发到重新登录 if (errMsg != null && !errMsg.equals("")) { rd = request.getRequestDispatcher("/login.jsp"); request.setAttribute("err", errMsg); rd.forward(request, response); } } @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // TODO Auto-generated method stub String errMsg = ""; // Servlet本身并不输出响应到客户端,因此必须将请求转发到视图页面 RequestDispatcher rd; // 获取请求参数 String username = req.getParameter("username"); String pass = req.getParameter("pass"); try { // Servlet本身并不执行任何的业务逻辑处理,它调用JavaBean处理用户请求 DbDao dd = new DbDao("com.mysql.jdbc.Driver", "jdbc:mysql://localhost:3306/liuyan", "root", "123456"); // 查询结果集 ResultSet rs = dd.query("select pass from user_inf" + " where name = ?", username); if (rs.next()) { // 用户名和密码匹配 if (rs.getString("pass").equals(pass)) { // 获取session对象 HttpSession session = req.getSession(true); // 设置session属性,跟踪用户会话状态 session.setAttribute("name", username); // 获取转发对象 rd = req.getRequestDispatcher("/welcome.jsp"); // 转发请求 rd.forward(req, resp); } else { // 用户名和密码不匹配时 errMsg += "您的用户名密码不符合,请重新输入"; } } else { // 用户名不存在时 errMsg += "您的用户名不存在,请先注册"; } } catch (Exception e) { e.printStackTrace(); } // 如果出错,转发到重新登录 if (errMsg != null && !errMsg.equals("")) { rd = req.getRequestDispatcher("/login.jsp"); req.setAttribute("err", errMsg); rd.forward(req, resp); } } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } }
DAO代码
package lee; import java.sql.*; /** * Description: * <br/>网站: <a href="http://www.crazyit.org">疯狂Java联盟</a> * <br/>Copyright (C), 2001-2016, Yeeku.H.Lee * <br/>This program is protected by copyright laws. * <br/>Program Name: * <br/>Date: * @author Yeeku.H.Lee kongyeeku@163.com * @version 1.0 */ public class DbDao { private Connection conn; private String driver; private String url; private String username; private String pass; public DbDao() { } public DbDao(String driver , String url , String username , String pass) { this.driver = driver; this.url = url; this.username = username; this.pass = pass; } // 下面是各个成员属性的setter和getter方法 public void setDriver(String driver) { this.driver = driver; } public void setUrl(String url) { this.url = url; } public void setUsername(String username) { this.username = username; } public void setPass(String pass) { this.pass = pass; } public String getDriver() { return (this.driver); } public String getUrl() { return (this.url); } public String getUsername() { return (this.username); } public String getPass() { return (this.pass); } // 获取数据库连接 public Connection getConnection() throws Exception { if (conn == null) { Class.forName(this.driver); conn = DriverManager.getConnection(url,username, this. pass); } return conn; } // 插入记录 public boolean insert(String sql , Object... args) throws Exception { PreparedStatement pstmt = getConnection().prepareStatement(sql); for (int i = 0; i < args.length ; i++ ) { pstmt.setObject( i + 1 , args[i]); } if (pstmt.executeUpdate() != 1) { return false; } pstmt.close(); return true; } // 执行查询 public ResultSet query(String sql , Object... args) throws Exception { PreparedStatement pstmt = getConnection().prepareStatement(sql); for (int i = 0; i < args.length ; i++ ) { pstmt.setObject( i + 1 , args[i]); } return pstmt.executeQuery(); } // 执行修改 public void modify(String sql , Object... args) throws Exception { PreparedStatement pstmt = getConnection().prepareStatement(sql); for (int i = 0; i < args.length ; i++ ) { pstmt.setObject( i + 1 , args[i]); } pstmt.executeUpdate(); pstmt.close(); } // 关闭数据库连接的方法 public void closeConn() throws Exception { if (conn != null && !conn.isClosed()) { conn.close(); } } }
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