连接数据库：C3P0
自动登录：COOKIE
注册：AJAX
一、代码
1.登录界面login.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>用户登录</title>
</head>
<body>
<div align="center">
${
sessionScope.message }<br>
<form action="login-check" method="post">
用户名：<input type="text" name="username"/><br>
<br>
密码： <input type="text" name="password"/><br>
<input type="checkbox" name="check" value="check"/>自动登录<br><br>
<input type="submit" value="提交"/>
<input type = "button" value = "注册" onclick = "window.location.href = 'register.jsp'">
</form>
</div>
</body>
</html>
2.核验用户名和密码LoginCheckServlet.java
C3P0连接数据库详解见点击此处
使用cookie实现自动登录
@WebServlet("/login-check")
public class LoginCheckServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
String message=null;
Connection dbconn=null;
DataSource dataSource = null;
boolean flag=false;
public void init() {
try {
ComboPooledDataSource comboPooledDataSource = new ComboPooledDataSource("hhh");
dataSource = comboPooledDataSource;
dbconn=dataSource.getConnection();
}catch(Exception e) {
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
String value1="";
String value2="";
Cookie cookie=null;
Cookie [] cookies=request.getCookies();
if(cookies!=null) {
for(int i=0;i<cookies.length;i++) {
cookie=cookies[i];
if(cookie.getName().equals("username"))
value1=cookie.getValue();
if(cookie.getName().equals("password"))
value2=cookie.getValue();
}
if(flag) {
response.sendRedirect("choose.jsp?username="+value1.toString()+"再次登录");
}else {
response.sendRedirect("login.jsp");
}
}else {
response.sendRedirect("login.jsp");
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
try {
String sql="select * from user where username = ? and password = ?";
PreparedStatement pstmt=dbconn.prepareStatement(sql);
pstmt.setString(1,request.getParameter("username"));
pstmt.setString(2,request.getParameter("password"));
ResultSet result=pstmt.executeQuery();
while(result.next()) {
flag=true;
}
}catch(SQLException e) {
e.printStackTrace();
}
String username=request.getParameter("username").trim();//trim()去掉用户名字符串的头尾两端空格
String password=request.getParameter("password").trim();
if(!flag){
message="用户名或密码不正确，请重试！";
request.getSession().setAttribute("message",message);
response.sendRedirect("login.jsp");
}else {
if((request.getParameter("check")!=null&&request.getParameter("check").equals("check"))) {
//选了记住密码
Cookie usernameCookie=new Cookie("username",username);
Cookie passwordCookie=new Cookie("password",password);
usernameCookie.setMaxAge(60*60*4);
passwordCookie.setMaxAge(60*60*4);
response.addCookie(usernameCookie);
response.addCookie(passwordCookie);
}
response.sendRedirect("choose.jsp?username="+username.toString());
}
}
}
3.注册界面register.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>用户注册</title>
<script type="text/javascript">
var xmlHttp;
function createXMLHttpRequest(){
if(window.ActiveXObject){
xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
}else if(window.XMLHttpRequest){
xmlHttp=new XMLHttpRequest();
}
}
function validate(){
createXMLHttpRequest();
var username=document.getElementById("username");
var url="validation.do?username="+escape(username.value);
xmlHttp.open("GET",url,true);
xmlHttp.onreadystatechange=handleStateChange;
xmlHttp.send(null);
}
function handleStateChange(){
if(xmlHttp.readyState==4){
if(xmlHttp.status==200){
var message=xmlHttp.responseXML.getElementsByTagName("message")[0].firstChild.data;
var messageArea=document.getElementById("results");
messageArea.innerHTML="<p>"+message+"</p>";
}
}
}
</script>
</head>
<body>
<form action="validation.do" method="post">
<div align="center">
<br><br>
<font size="4" color=red ><div id="results">请输入用户名和密码</div></font><br>
*用户名：<input type="text" id="username" name="username" size="20"onblur="validate()";><br>
<br>
*密码： <input type="text" id="password" name="password" size="20"><br>
<br>
<input type="submit" name="submit" value="提交">
<input type="reset" name="reset" value="重置">
</div>
</form>
</body>
</html>
4.ValidationServlet.java
光标移动到密码框里时显示用户名可否被使用的信息
点击提交将用户名和密码添加入数据库
注册成功则返回登录界面
@WebServlet(name="validationServlet",urlPatterns= {
"/validation.do"})
public class ValidationServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
Connection dbconn=null;
DataSource dataSource = null;
public void init() {
try {
ComboPooledDataSource comboPooledDataSource = new ComboPooledDataSource("hhh");
dataSource = comboPooledDataSource;
dbconn=dataSource.getConnection();
}catch(Exception e) {
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.setContentType("text/xml;charset=UTF-8");
response.setHeader("Cache-Control", "no-cache");
String message="该用户名可以被使用";
String username=request.getParameter("username");
String sql="SELECT * FROM user WHERE username=?";
try {
PreparedStatement pstmt=dbconn.prepareStatement(sql);
pstmt.setString(1, username);
ResultSet rst=pstmt.executeQuery();
if(rst.next())
message="该用户名已被使用，请更换其他用户名！";
}catch(SQLException sqle) {
System.out.println(sqle);
}
PrintWriter out=response.getWriter();
out.println("<response>");
out.println("<message>"+message+"</message>");
out.println("</response>");
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.setContentType("text/html;charset=utf-8");
String username=request.getParameter("username");
String password=request.getParameter("password");
try {
String sql="INSERT INTO user VALUES(?,?)";
PreparedStatement pstmt=dbconn.prepareStatement(sql);
pstmt.setString(1, username);
pstmt.setString(2, password);
if(pstmt.executeUpdate()>0)
{
JOptionPane.showMessageDialog(null, "注册成功！");
request.getRequestDispatcher("login.jsp").forward(request,response);}
}catch(SQLException e) {
System.out.println(e);
}
}
}
二、运行结果截图
1.登录界面
2.数据库里已存在Wangqiang所以提示"该用户名已被使用，请更换其他用户名！"
3.数据库里不存在Wangmei，所以提示"该用户名可以被使用"
