Ajax校验用户名是否可用

准备

导包：DBUtil，JDBC，C3P0
在src下导入c3p0-config.xml
导入JDBCUtil
创建数据库

第2.3.条查看https://blog.csdn.net/weixin_44718300/article/details/88994973

1、新建JSP页面

<body>

   	<table border="1" width="500">

   		<tr>

   			<td>用户名:</td>

   			<td><input type="text" name="name" id="name"  οnblur="checkUserName()"><span id="span01"></span></td>

   		</tr>

   		<tr>

   			<td>密码</td>

   			<td><input type="text" name=""></td>

   		</tr>

   		<tr>

   			<td>邮箱</td>

   			<td><input type="text" name=""></td>

   		</tr>

   		<tr>

   			<td>简介</td>

   			<td><input type="text" name=""></td>

   		</tr>

   		<tr>

   			<td colspan="2"><input type="submit" value="注册"></td>

   		</tr>

   	</table>

</body>

2、创建Servlet

public class CheckUserNameServlet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		try {

			request.setCharacterEncoding("UTF-8");

			//1. 检测是否存在

			String name = request.getParameter("name");

			System.out.println("name="+name);

			UserDao dao = new UserDaomImpl();

			boolean isExist = dao.checkUserName(name);

			//2.  通知页面，到底有还是没有。

			if(isExist){

				response.getWriter().println(1);  //存在用户名

			}else{

				response.getWriter().println(2); //不存在该用户名

			}

		} catch (SQLException e) {

			e.printStackTrace();

		}

	}

	/**

	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)

	 */

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		doGet(request, response);

	}

}

3、Dao

boolean checkUserName(String username) throws SQLException;

@Override

	public boolean checkUserName(String username) throws SQLException {

		QueryRunner runner = new QueryRunner(JDBCUtil02.getDataSource());

		String sql = "select count(*) from t_user where username =?";

		runner.query(sql, new  ScalarHandler(), username);

		Long result = (Long) runner.query(sql, new  ScalarHandler(), username);

		return result > 0 ;

	}

4、修改jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"

	pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>Insert title here</title>

<script type="text/javascript">

	//1. 创建对象

	function  ajaxFunction(){

	   var xmlHttp;

	   try{ // Firefox, Opera 8.0+, Safari

	        xmlHttp=new XMLHttpRequest();

	    }

	    catch (e){

		   try{// Internet Explorer

		         xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");

		      }

		    catch (e){

		      try{

		         xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");

		      }

		      catch (e){}

		      }

	    }

		return xmlHttp;

	 }

	function checkUserName() {

		//获取输入框的值 document 整个网页

		var name = document.getElementById("name").value; // value  value() val val()

		//1. 创建对象

		var request = ajaxFunction();

		//2. 发送请求

		request.open("POST"  ,"/day16/CheckUserNameServlet" , true );

		//注册状态改变监听，获取服务器传送过来的数据

		request.onreadystatechange = function(){

			if(request.readyState == 4 && request.status == 200){

				//alert(request.responseText);

				var data = request.responseText;

				if(data == 1){

					//alert("用户名已存在");

					document.getElementById("span01").innerHTML = "<font color='red'>用户名已存在!</font>";

				}else{

					document.getElementById("span01").innerHTML = "<font color='green'>用户名可用!</font>";

					//alert("用户名未存在");

				}

			}

		}

		request.setRequestHeader("Content-type","application/x-www-form-urlencoded");

		request.send("name="+name);

	}

</script>

</head>

<body>

<body>

	<table border="1" width="500">

		<tr>

			<td>用户名:</td>

			<td><input type="text" name="name" id="name"  οnblur="checkUserName()"><span id="span01"></span></td>

		</tr>

		<tr>

			<td>密码</td>

			<td><input type="text" name=""></td>

		</tr>

		<tr>

			<td>邮箱</td>

			<td><input type="text" name=""></td>

		</tr>

		<tr>

			<td>简介</td>

			<td><input type="text" name=""></td>

		</tr>

		<tr>

			<td colspan="2"><input type="submit" value="注册"></td>

		</tr>

	</table>

</body>

</html>

巴特西

Ajax校验用户名是否可用

准备

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