POST request saving all values to one column

I'm using Postman to send a POST request with some values(I put two strings, one is for username and the other is for mail), but all data gets saved to first column ("username"). What am I doing wrong?

This is what I've tried.

{
    "username": "mm46676",
    "mail": "mm46676@gmail.com"
}

I expected mm46676 is going to be saved in username column and mm46676@gmail.com to be saved in mail column. I'm using H2 console to see how it was saved in db.

EmployeeController.java

import com.incompatibleTypes.plancation.plancationapp.model.Employee;
import com.incompatibleTypes.plancation.plancationapp.repository.EmployeeRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.*;

@Controller
@RequestMapping(path = "/employee")
public class EmployeeController {

    private final EmployeeRepository employeeRepository;

    public EmployeeController(EmployeeRepository employeeRepository) {
        this.employeeRepository = employeeRepository;
    }

    @GetMapping("/all")
    public @ResponseBody Iterable<Employee> showAllEmployees(){
        return employeeRepository.findAll();
    }

    @PostMapping(path = "/add")
    public @ResponseBody String addNewEmployee (@RequestBody String username, String mail){
        Employee employee = new Employee();
        employee.setUsername(username);
        employee.setMail(mail);
        employeeRepository.save(employee);
        return "Employee Saved!";
    }
}

Employee model(if it can help in any way)

package com.incompatibleTypes.plancation.plancationapp.model;

import jakarta.persistence.*;
import lombok.Data;


import java.time.LocalDateTime;
import java.util.HashSet;
import java.util.Set;
import java.util.UUID;

@Data
@Entity
@Table(name = "employee")
public class Employee {
    @Id
    @GeneratedValue(strategy = GenerationType.UUID)
    private UUID id;

    private Role role;
    @Column(name = "username")
    private String username;
    @Column(name = "mail")
    private String mail;

    @OneToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "department_id")
    private Department department;


    @ManyToOne
    @JoinColumn(name = "minimal_vacation_day_id") 
    private VacationDay minimalVacationDay;
    @ManyToMany
    @JoinTable(
            name = "employee_bonusvacdays",
            joinColumns = @JoinColumn(name = "bonus_vacation_day_id"),
            inverseJoinColumns = @JoinColumn(name = "employee_id")
    )
    private Set<BonusVacationDay> bonusVacationDays = new HashSet<>();
    private LocalDateTime dateEmployed;

}

Solution

The problem in your code is when passing the request body as a method parameter. With this code:

public @ResponseBody String addNewEmployee (@RequestBody String username, String mail)

the whole JSON body goes as a String to the variable username. You should pass an object with fields username and mail instead. This can be the entity or - even better - a dedicated POJO aka as DTO. Something like this:

public @ResponseBody String addNewEmployee (@RequestBody EmployeeDTO data) {
    Employee employee = new Employee();
    employee.setUsername(data.getUsername());
    employee.setMail(data.getMail());
    employeeRepository.save(employee);
    return "Employee Saved!";
}