json转java对象
使用步骤：
1、导入jackson的相关jar包
2、创建Jackson核心对象 ObjectMapper
3、调用ObjectMapper的相关方法进行转换
1、readValue(json字符串数据,Class);
@Test
public void test5() throws IOException {
//1、初始化JSON字符串
String json = "{\"gender\":\"男\",\"name\":\"张三\",\"age\":\"23\"}";
//2、创建ObjectMapper对象
ObjectMapper mapper = new ObjectMapper();
//3、转换为java对象，Person对象
Person person = mapper.readValue(json, Person.class);
System.out.println(person);
}
校验用户名是否存在案例
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");
案例实现：
regist.html:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</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实践
$("#username").blur(function () {
//获取username文本输入框的值
var username = $(this).val();
//发送ajax请求
//期望服务器响应回的数据格式：{"userExsit":true,"msg":"此用户名太受欢迎，请更换一个"}
// {"userExsit":false,"msg":"用户名可用"}
$.get("findUserServlet",{username:username},function (data) {
//判断userExsit键的值是否是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>
FindUserServlet类：
@WebServlet("/findUserServlet")
public class FindUserServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1、获取用户名
String username = request.getParameter("username");
//2、调用service层判断用户名是否存在
//期望服务器响应回的数据格式：{"userExsit":true,"msg":"此用户名太受欢迎，请更换一个"}
// {"userExsit":false,"msg":"用户名可用"}
response.setContentType("text/html;charset=utf-8");
// response.setContentType("application/json;charset=utf-8");
HashMap<String, Object> map = new HashMap<>();
if ("tom".equals(username)){
//存在
map.put("userExsit",true);
map.put("msg","此用户名太受欢迎，请更换一个");
}else {
//不存在
map.put("userExsit",false);
map.put("msg","用户名可用");
}
//将map转为json
ObjectMapper mapper = new ObjectMapper();
//并且传递给客户端
mapper.writeValue(response.getWriter(),map);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
标签：username,用户名,java,userExsit,校验,json,msg,ObjectMapper From： https://www.cnblogs.com/xjw12345/p/16609403.html