我必须创建一个web应用程序，在mysql数据库中添加一个用户，并使用emberjs实现ui。
应用程序/组件/用户.hbs

<h1>User Management!</h1>
<div>   
    <label1>User Id </label1>   <colon1>:</colon1>
    <input1>{{input type="text" value=id placeholder="Enter id"}}</input1>
    <label2>Firstname</label2>  <colon2>:</colon2>
    <input2>{{input type="text" value=firstname placeholder="Enter firstname"}}</input2>
    <label3>Lastname</label3>   <colon3>:</colon3>
    <input3>{{input type="text" value=lastname placeholder="Enter lastname"}}</input3>
    <label4>Mail Id</label4>    <colon4>:</colon4>
    <input4>{{input type="text" value=mailid placeholder="Enter mailid"}}</input4>
</div>
    <button1 {{on "click" (fn this.user "add" id firstname lastname mailid )}}>Add User</button1>
    <button2 {{on "click" (fn this.user "delete" id firstname lastname mailid )}}>Delete User</button2>

应用程序/组件/用户.js

import Component from '@glimmer/component';
import {action} from "@ember/object";
import {tracked} from "@glimmer/tracking";

export default class UserComponent extends Component {
    @action 
    async user (type,id,firstname,lastname,mailid){
        let response=await fetch("http://localhost:8080/UserManagement/UserManagementServlet",
        {   method: "POST",
            mode:"no-cors",
            headers: { 'Content-Type': 'application/json'},
            body: JSON.stringify({
                "type": type,
                "id": id,
                "firstname":firstname,
                "lastname":lastname,
                "mailid":mailid
            })
        });
        let parsed=await response.json();
        alert(parsed.status);
    }
}

servlet api代码

//Required Header files
@WebServlet("/UserManagementServlet")
public class UserManagementServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    protected void doPost(HttpServletRequest req,HttpServletResponse res) throws ServletException, IOException 
    {   res.setContentType("application/json");  
        res.setCharacterEncoding("UTF-8");
        Gson gson=new Gson();
        BufferedReader br=new BufferedReader(new InputStreamReader(req.getInputStream()));
        String param=br.readLine();
        User user = gson.fromJson(param, User.class);
        HashMap<String,String> jsonfile=new HashMap<String,String>();
        PrintWriter out=res.getWriter();
        String url="jdbc:mysql://localhost:3306/employee",username="root";
        String password="root";
        Connection con=null;
        PreparedStatement pst;
        String query="select*from user";
        ResultSet rs;
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            con = DriverManager.getConnection(url,username, password);
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println("Entered");
        if (user.getType().equals("add")) {
            try {
                String insertquery="INSERT INTO user" +"  (id,firstname,lastname,  mailid) VALUES " +" (?,?, ?, ?);";
                pst = con.prepareStatement(insertquery);
                pst.setString(1, String.valueOf(user.getId()));
                pst.setString(2, user.getFirstName());
                pst.setString(3, user.getLastName());
                pst.setString(4, user.getMailid());

                jsonfile.put("id", String.valueOf(user.getId()));
                jsonfile.put("firstname", user.getFirstName());
                jsonfile.put("lastname", user.getLastName());
                jsonfile.put("mailid", user.getMailid());
                jsonfile.put("status","User Added Successfully");

                String final1=gson.toJson(jsonfile);
                System.out.println(final1);
                out.println(final1);

                pst.executeUpdate();   
            } catch (Exception e) {
                out.println("error"+e);
            }
        }
        out.flush();
    }
}

它显示cors错误，所以我在user.js中添加了“mode”：“no cors”，但是在那之后cors错误消失了，但是这个错误没有。
单击adduser按钮时，它会在以下行显示错误“let parsed=await response.json（）；”

user.js:54 Uncaught (in promise) SyntaxError: Unexpected end of input
    at UserComponent.user (user.js:54)"