jquery 的ajax
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'ajax.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<input type="text" name="userName" onblur="validate();"><div></div>
<script type="text/javascript" src="js/jquery-1.12.4.js"></script>
<script type="text/javascript">
//输入框失去焦点 触发的事件
function validate(){
//获取用户的输入
var $name=$("[name='userName']").val();
//非空验证
if($name==null || $name==""){
$("[name='userName']").next().html("<span style='color:red'>用户名不能为空！！！</span>");
}else{
$.ajax({
url:"LoginServlet",
data:"name="+$name,
type:"POST",
dataType:"json",
beforeSend:function(){
alert("初始化参数。。。。。请稍后！！！！");
},
success:function(data){//预期返回数据的类型
if(data.flag=="true"){
$("[name='userName']").next().html("<span style='color:red'>用户名已存在！！！</span>");
}else{
$("[name='userName']").next().html("<span style='color:green'>用户名可以使用！！！</span>");
}
},
error:function(){
alert("请求有误");
}
})
}
}
</script>
</body>
</html>
package cn.bdqn.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
// TODO Auto-generated method stub
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
String name = req.getParameter("name");
boolean flag = false;
if ("admin".equals(name)) {
flag = true;
}
String out = "{\"flag\":\"" + flag + "\"}";
System.out.println(out);
PrintWriter writer = resp.getWriter();
writer.print(out);
writer.flush();
writer.close();
}
public static void main(String[] args) {
int a = 128;
int b = 128;
System.out.println(a == b);
Integer a1 = 127;
Integer a2 = 127;
Integer a3 = 128;
Integer a4 = 128;
System.out.println(a1 == a2);
System.out.println(a3 == a4);
Integer b1 = new Integer(127);
Integer b2 = new Integer(127);
System.out.println(b1 == b2);
Integer c1 = Integer.valueOf(127);
Integer c2 = Integer.valueOf(127);
System.out.println(c1 == c2);
}
}
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