GET
AjaxServlet.java
@WebServlet("/ajax")
public class AjaxServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8" );
PrintWriter out = response.getWriter();
String old = request.getParameter("username" );
if (old == null || old.length() == 0 ) {
out.println("用户名不能为空" );
} else {
if (old.equals( "admin" )) {
out.println("用户名 [" + old + "] 已经存在，请使用其他用户名" );
} else {
out.println("用户名 [" + old + "] 尚未存在，可以使用该用户名注册" );
}
}
}
}
ajax.html
<html>
<head>
<title>ajax</title>
<script src="https://code.jquery.com/jquery-3.2.1.min.js"></script>
</head>
<body>
<input type="text" id="username"/>
<input type="button" value="11" onclick="verify();"/>
<div id="result"></div>
</body>
<script>
function verify(){
var jqueryObj = $("#username");
var username = jqueryObj.val();
$.get("/ajax?username=" + username, null, callback);
}
function callback(data){
$("#result").html(data);
}
</script>
</html>
POST
LoginServlet.java
@WebServlet("/login")
public class LoginServlet extends HttpServlet {
public static final String DBDRIVER = "com.mysql.jdbc.Driver";
public static final String DBURL = "jdbc:mysql://localhost:3306/login?useSSL=false";
public static final String DBUSER = "root";
public static final String DBPASS = "123";
boolean flag = false;
String username = null;
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
Connection conn = null; //数据库连接
PreparedStatement pstmt = null; //数据库预处理操作
ResultSet rs = null; //查询要处理结果集
try{
Class.forName(DBDRIVER);
conn = DriverManager.getConnection(DBURL,DBUSER,DBPASS);
String sql = "select username from user where username = ? and password = ?";
pstmt = conn.prepareStatement(sql);
pstmt.setString(1, request.getParameter("username"));
pstmt.setString(2, request.getParameter("password"));
rs = pstmt.executeQuery();
if(rs.next()){ //如果有数据就执行
flag = true; //表示登陆成功
username = rs.getString(1);
}
System.out.println(username);
} catch (Exception e){
e.printStackTrace();
} finally{
try{
rs.close();
pstmt.close();
conn.close();
}catch(Exception e){
e.printStackTrace();
}
}
response.setContentType("text/html; charset=UTF-8");
PrintWriter out=response.getWriter();
if(flag == true) {
out.println("success");
} else {
out.print("error");
}
out.flush();
out.close();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request,response);
}
}
login.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Ajax</title>
<script src="https://code.jquery.com/jquery-3.2.1.min.js"></script>
</head>
<body>
<form action='/login' id='addForm' type='post'>
用户名：<input type='text' id='username' name="username" value=""><br>
密码：<input type='password' id='password' name="password" value=""><br>
<input type='button' value='提交' onclick='login()'>
</form>
<label id="msg"></label>
</body>
<script type="text/javascript">
function login(){
var user = {
username:"admin",
password:"123456"
};
var username = $('#username').val();
var password = $('#password').val();
if ("" == name || "" == pwd) {
alert('用户名或者密码不能为空');
} else {
$.ajax({
url: 'http://localhost:8080/login?username=' + username + '&password=' + password,
type: 'post',
success: function (data) {
if('success' == data) {
// location.href='<%=basePath%>/index.jsp'
window.location.reload();
} else {
$('#msg').html(msg);
}
}
})
}
}
function login2(){
$.ajax({
url: 'http://localhost:8080/login', // 不能在末尾再加一个/，不然出现404
data: $('#addForm').serialize(),
type: 'post',
contentType: 'application/x-www-form-urlencoded; charset=UTF-8', //防止乱码
success:function(data){
console.log('添加成功');
console.log(data);
}
})
}
</script>
</html>
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