JavaScript失去焦点实时验证用户名是否存在(笔记)

1.controller层 

    //注册检查用户名是否存在
    @RequestMapping("/checkregister")
    public void checkregister(HttpServletRequest request, HttpServletResponse response) throws IOException {
        response.setCharacterEncoding("utf-8");
        String username = request.getParameter("username");
        Map<String, Object> map = new HashMap<String, Object>();
        User user = userService.queryUser(username);
        if (user != null) {
            map.put("userExist", true);
            map.put("msgInfo", "用户名已存在");
        } else {
            map.put("userExist", false);
            map.put("msgInfo", "用户名可以使用");
        }
        ObjectMapper om = new ObjectMapper();
        om.writeValue(response.getWriter(), map);

    }

2.mapper层

    @Select("select * from user where username=#{username}")
    public User queryUser(String username);

3.service层

//查询数据库中该用户是否存在 
public User queryUser(String username);

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    UserMapper userMapper;

    @Override
    public User queryUser(String username) {
        return userMapper.queryUser(username);
    }
}

4.jsp页面

 <form method="post" action="<%=path%>/houseWeb/register">
                <h2>立即注册</h2>
                <label>
                    <span>用户名</span>
                    <input type="text" id="u_loginName" name="username" required>
                    <span id="msg0"></span>
                </label>
                <label>
                    <span>密码</span>
                    <input type="password" id="password" name="password" required>
                </label>
                <label>
                    <span>再次输入密码</span>
                    <input type="password" id="newPassword" name="newPassword" required onkeyup="checkPassword()">
                </label>
                <div id="msg3"></div>
                <button type="submit" class="submit" id="btn">注 册</button>
                <span style="color: red">${msg1}</span>
            </form>

       
<script>
    function checkPassword() {
        var password = document.getElementById("password").value;  //js语法
         var newPassword=document.getElementById("newPassword").value;
        // var password = $("#password").value;//jquery语法
        // var newPassword = $("#newPassword").value;
        if (password != newPassword) {
            document.getElementById("msg3").innerHTML = "<span style='color: red'>两次密码不一致</span>";
            document.getElementById("btn").disabled = true;
        } else {
            document.getElementById("msg3").innerHTML = "<span style='color: green'>两次密码一致</span>";
            document.getElementById("btn").disabled = false;
        }
    }

    $(function () {
        //id为usernameTag的输入框失去焦点后触发
        $("#u_loginName").blur(function () {
            var username = $(this).val();
            var msg = $("#msg0");

            //如果用户名为空则不判断，并清空之前判断的提示信息
            if(username == ''){
                msg.html(null);
                return false;
            }

            //data里存放的是后台返回给前端的数据
            $.post("checkregister",{"username":username},function (data) {
                if(data.userExist){
                    msg.html(data.msgInfo);
                    msg.css("color","red");
                    //若用户名存在则提交按钮禁止点击
                    document.getElementById("button").disabled = true;
                }else {
                    msg.html(data.msgInfo);
                    msg.css("color","green");
                    //若用户名不存在则提交按钮可以点击
                    document.getElementById("button").disabled = false;

                }
            },"json");
        });
    });

</script>