ajax实时验证用户名是否存在
1、jsp页面
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
ajax验证用户名是否可用
2、web.xml
AjaxServlet com.servlet.AjaxServlet AjaxServlet /ajax
3、servlet
package com.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class AjaxServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
String userName = request.getParameter("userName");
if(userName.equals("admin")){
out.print("用户名已经存在");
}
else if (userName.length() == 0) {
out.print("用户不能为空");
}
else if (userName.indexOf(" ") > 0) {
out.print("用户不能含有空格");
}
else if (userName.length() > 10 || userName.length() < 4) {
out.print("用户长度在4-10之间");
}
else {
out.print("用户名可用");
}
out.flush();
out.close();
}
} 
