enter code here
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.Iterator;

import org.apache.commons.io.IOUtils;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;
import net.sf.json.JSONSerializer;

@SpringBootApplication
public class DemoRProjetSpringAppApplication {
    private static String tableName = "etudiants";
    public static void main(String[] args) {
        SpringApplication.run(DemoRProjetSpringAppApplication.class, args);



    try {

           ClassLoader cl =DemoRProjetSpringAppApplication.class.getClassLoader();
           InputStream is = cl.getResourceAsStream("etudiants.json");
           String str = IOUtils.toString(is);
           JSONObject jsonObject = (JSONObject) JSONSerializer.toJSON(str);
           JSONArray jsonArr = jsonObject.getJSONArray("profiles");
           JSONObject obj = null;
           JSONArray nameArr = null;
           JSONArray valArr = null;

           for (int i = 0; i < jsonArr.size(); i++) {
            obj = jsonArr.getJSONObject(i);
            nameArr = obj.names();
            valArr = obj.toJSONArray(nameArr);
            saveRecord(nameArr, valArr);
           }
          } catch (Exception e) {
           e.printStackTrace();
          }
         }
         private static void saveRecord(JSONArray nameArray, JSONArray valArray) {
          Connection conn = getConnection();
          StringBuffer sb = new StringBuffer("insert into " + tableName + "(");
          int size = nameArray.size();
          int count = 0;
          Iterator<Object> iterator = nameArray.iterator();

          while (iterator.hasNext()) {
           if (count < (size - 1))
            sb.append(iterator.next() + ",");
           else
            sb.append(iterator.next() + ")");
           count++;
          }
          sb.append(" values(");

          for (int i = 0; i < size; i++) {
           if (i < (size - 1))
            sb.append("?,");
           else
            sb.append("?)");
          }
          System.out.println(sb.toString());
          try {
           PreparedStatement pstmt = conn.prepareStatement(sb.toString());
           bindVariables(valArray, pstmt);
           pstmt.executeUpdate();
          } catch (SQLException e) {
           e.printStackTrace();
          }
         }
         private static void bindVariables(JSONArray valArray,
           PreparedStatement pstmt) throws SQLException {
          Iterator<Object> iterator = valArray.iterator();
          int cnt = 0;
          while (iterator.hasNext()) {
           Object obj = iterator.next();
           if (obj instanceof String) {
            pstmt.setString(++cnt, (String) obj);
           } else if (obj instanceof Integer) {
            pstmt.setLong(++cnt, (Integer) obj);
           } else if (obj instanceof Long) {
            pstmt.setLong(++cnt, (Long) obj);
           } else if (obj instanceof Double) {
            pstmt.setDouble(++cnt, (Double) obj);
           }
          }
         }
         private static Connection getConnection() {
          Connection con = null;
          String url = "jdbc:mysql://localhost:3306/";
          String db =  "projet2";
          String driver = "com.mysql.jdbc.Driver";
          String user = "root";
          String pass = "password";
          try {
           Class.forName(driver);
           con = DriverManager.getConnection(url + db, user, pass);
          } catch (ClassNotFoundException e) {
           e.printStackTrace();
          } catch (SQLException e) {
           e.printStackTrace();
          }
          return con;
         }
}

enter code here

import java.util.List;
import javax.persistence.Entity;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import java.util.List;

import javax.persistence.Entity;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.OneToOne;
import javax.persistence.Table;

@Entity
@Table(name = "etudiants")
public class Student extends User {
    @ManyToOne
    private Grade grade;


    public Grade getGrade() {
        return grade;
    }
    public void setGrade(Grade grade) {
        this.grade= grade;
    }

    public Student() {
        super();
    }

    public Student(Integer id) {
        super(id);
    }
    public Student(String firstname, String lastname, String login,
            String email, String password,UserType student) {
        super(firstname, lastname, login,email, password,student);
    }
    public Student(String firstname, String lastname, String login,
            String email,String password,UserType student,Grade grade) {
        super(firstname, lastname, login,email, password, student);
        this.grade = grade;

    }
    public Student(String firstname, String lastname, String login,String email,
            String password,UserType student,Grade grade,UserType STUDENT) {
        super(firstname, lastname, login,email, password,student);
        this.grade = grade;

    }
}

enter code here
    {"profiles":[{"id":1, "email":"NULL", "firstname":"MARY", "lastname":"mahdi", "login":"mdi.MARY", "password":"pass", "userTypeID":2, "grade_id":1},
 {"id":2, "email":"jasmin.mal@hotmail.fr", "firstname":"jasmin", "lastname":"Mal", "login":"jasmin.Mal", "password":"pass", "userTypeID":2, "grade_id":1},
 {"id":3, "email":"kira.muip@msn.com", "firstname":"muip", "lastname":"kira", "login":"kira.muip", "password":"pass", "userTypeID":2, "grade_id":1}]
 }