校验用户名是否存在案例
1.服务器响应的数据，在客户端使用时，要想当做json数据格式使用
1.$.get(type)：将最后一个参数type指定为"json"
2.在服务器端设置MIME类型
response.setContentType("application/json;charset=utf-8");
FindUserServlet:
@WebServlet("/findUserServlet")
public class FindUserServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获取用户名
String username = request.getParameter("username");
//调用service层判断用户名是否存在
response.setContentType("text/html;charset=utf-8");
//response.setContentType("application/json;charset=utf-8");
Map<String, Object> map = new HashMap<String, Object>();
if ("tom".equals(username)){
//存在
map.put("userExsit",true);
map.put("msg","此用户名存在,请换一个");
}else {
//不存在
map.put("userExsit",false);
map.put("msg","用户名可以使用");
}
//将map转为json，并且传递给客户端
ObjectMapper mapper = new ObjectMapper();
mapper.writeValue(response.getWriter(),map);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
5-regist.html:页面
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>注册页面</title>
<script src="js/jquery-3.3.1.min.js"></script>
<script>
//在页面加载完成后
$(function () {
//给username绑定blur事件
$("#username").blur(function () {
//获取username文本输入框的值
var username = $(this).val();
//发送ajax请求
//期望服务器响应的数据格式：{"userExsit":true,"msg":"此用户名存在,请换一个"}
// {"userExsit":false,"msg":"用户名可以使用"}
$.get("findUserServlet",{username:username},function (data) {
//判断userExsit键的值是否存在true
var span = $("#s_username");
if (data.userExsit){
//用户名存在
span.css("color","red");
span.html(data.msg);
}else {
//用户名不存在
span.css("color","green");
span.html(data.msg);
}
},"json");
});
});
</script>
</head>
<body>
<form>
<input type="text" id="username" name="username" placeholder="请输入用户名">
<span id="s_username"></span>
<br>
<input type="password" name="password" placeholder="请输入密码"><br>
<input type="submit" value="注册"><br>
</form>
</body>
</html>
搜索
复制
标签：username,map,用户名,校验,案例,json,msg,response From： https://www.cnblogs.com/pengtianyang/p/16609613.html