1、程序所需的代码：
1）<%@ 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>
<center>
<form action="loginResult.jsp" method="post" >
<br><br><br><br><br><br>
<table>
<tr><td>用户名：</td><td><input type="text" name="userName" id="user"><span id="userInfo" ></span></td></tr>
<tr><td>密码：</td><td><input type="password" name="userPwd" id="pwd"><span id="pwdInfo"></span></td></tr>
<tr><td></td><td><input type="submit" value="登 录"></td>
</table>
</form>
</center>
</body>
</html>
2） Connection conn = null;
PreparedStatement pstmt = null;
ResultSet rs = null;
String driverName = "com.mysql.jdbc.Driver";
String userName = "root";
String userPwd = "196521";
String dbName = "test2";
String url1 = "jdbc:mysql://localhost:3306/" + dbName;
String url2 = "?user=" + userName + "&password=" + userPwd;
String url3 = "&useUnicode=true&characterEncoding=UTF-8";
String url = url1 + url2 + url3;
request.setCharacterEncoding("UTF-8");
Class.forName(driverName);
conn = DriverManager.getConnection(url);
String sql = "select * from userInfo where username=?";
pstmt = conn.prepareStatement(sql);
String user = request.getParameter("userName");
String password = request.getParameter("userPwd");
pstmt.setString(1, user);
rs = pstmt.executeQuery();
if(rs.next()) {
sql = "select * from userInfo where username=? and password=?";
pstmt = conn.prepareStatement(sql);
pstmt.setString(1, user);
pstmt.setString(2, password);
rs = pstmt.executeQuery();
if(rs.next()) {
%><center><h1>用户 <%=rs.getString("username")%>登陆成功！</h1></center><%
}
else {
%><center><h1>密码错误！</h1></center><%
}
}
else {
%><center><h1>用户名不存在！</h1></center>
<%}
if(rs != null) {
rs.close();
}
if(pstmt != null) {
pstmt.close();
}
if(conn != null) {
conn.close();
}
%>
2、相应的截图：
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