jQuery ajax简单案例-验证用户名是否可用


HTML


<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<script type="text/javascript" src="/jquery_ajax/js/jquery-1.8.3.js"></script>
<script type="text/javascript">
    //页面加载完成后
    $(function() {
        //添加失焦事件
        $("#username").blur(function() {
            //获取录入的用户名
            var usernamevalue = $("#username").val();
            //向服务器发送请求
            var url="/jquery_ajax/load";
            $("#username_span").load(url,{'username':usernamevalue});
        });

    });
</script>
</head>
<body>

    <input type="text" name="username" id="username"><span id="username_span"></span>
    <br>
    <input type="password" name="password">
    <br>

</body>
</html>


LoginServlet


public class LoadServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 解决乱码
        request.setCharacterEncoding("utf-8");
        response.setCharacterEncoding("utf-8");
        // 1.得到用户名
        String username = request.getParameter("username");

        // 2.判断用户名是否可以使用
        if ("tom".equals(username)) {
            // 用户名不可以使用
            response.getWriter().write("<font color='red'>用户名被占用</font>");
        } else {
            // 用户名可以使用

            response.getWriter().write("<font color='green'>用户名可以使用</font>");
        }
    }

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

        doGet(request, response);
    }

}


web.xml


<servlet>
    <description></description>
    <display-name>LoadServlet</display-name>
    <servlet-name>LoadServlet</servlet-name>
    <!-- 
        Class clazz = Class.forName("com.zxl.servlet.LoadServlet");
        Object obj = clazz.newInstatnce();
        // 反射去调用 doGet, doPost
     -->
    <servlet-class>com.zxl.servlet.LoadServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>LoadServlet</servlet-name>
    <url-pattern>/load</url-pattern>
  </servlet-mapping>