mysql数据处理实例，java用户登录处理

概述：实现登录功能，用户输入帐号和密码，通过form表单提交至后台处理，查询数据库，如果用户名和密码均正确，则弹框提示用户登录成功，否则提示登录失败。

开发工具：eclipse Mars.2 Release (4.5.2)
服务器 ：apache-tomcat-7.0.68
数据库：MySql

前台源码：用到了简单的 bootstrap 和 jquery
后台代码：使用了servlet

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
response.setContentType("text/html; charset=UTF-8");

//mysql数据库驱动
String driver = "com.mysql.jdbc.Driver";
//链接数据库的url test为数据库名
String url = "jdbc:mysql://127.0.0.1:3306/test";
//数据库用户
String user = "root";
//数据库密码
String password = "root";

//从前台读取到的用户名
String username = request.getParameter("username");
//从前台读取到的密码
String pwd = request.getParameter("pwd");

//数据库链接成功时返回的实例
Connection conn = null;
//查询成功时返回的记录集
ResultSet rs = null;
try{
//加载驱动
Class.forName(driver);
//获取链接
conn = (Connection) DriverManager.getConnection(url, user, password);
//准备sql查询
String sql = "select * from User where username=? and pwd=?";
//使用PreparedStatement，可以防止sql注入
PreparedStatement ps = conn.prepareStatement(sql);
ps.setString(1, username);
ps.setString(2, pwd);
//执行查询,返回记录集 
rs = ps.executeQuery();
//如果查询到用户名和密码，则允许用户登录
if (rs.next()){
System.out.println("login ok!!");
PrintWriter out = response.getWriter();
out.flush();
out.println("<script>");
out.println("alert('恭喜，登录成功');");
out.println("history.back();");
out.println("</script>");
out.close();
}else{
System.out.println("login fail!!");
PrintWriter out = response.getWriter();
out.flush();
out.println("<script>");
out.println("alert('很遗憾，用户名或密码错误');");
out.println("history.back();");
out.println("</script>");
out.close();
}
//关闭PreparedStatement
ps.close();

}catch(Exception e){
e.printStackTrace();
}finally{
//最后一定要关闭链接
if (conn != null){
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(rs != null){
try {
rs.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
doGet(request, response);
}