AutoIncrement Id PostgreSQL and Spring Boot Data JPA

Question

I'm having problems trying to create a new record in my PostgreSQL database. I just want to POST to the REST service a new user (int:id, String:email, String:password) but, I'm having this error:

"exception": "org.springframework.dao.DataIntegrityViolationException",
"message": "could not execute statement; SQL [n/a]; constraint [id]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement

These are my Java classes:

Domain

@Entity
@Table(name = "users")
public class User {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Integer id;
  private String email;
  private String password;

  public User() {}

  public Integer getId() {
    return id;
  }

  public void setId(Integer id) {
    this.id = id;
  }

  public String getEmail() {
    return email;
  }

  public void setEmail(String email) {
    this.email = email;
  }

  public String getPassword() {
    return password;
  }

  public void setPassword(String password) {
    this.password = password;
  }
}

Controller

@RestController
@RequestMapping("/users")
public class UserController {
  @Autowired
  private UserService userService;

  @RequestMapping(method = RequestMethod.GET)
  public List<User> findAll() {
    return userService.findAll();
  }

  @RequestMapping(method = RequestMethod.POST)
  public User addUser(@RequestBody User user) {
    userService.addUser(user);
    return user;
  }
}

Service

@Service
public class UserService {
  @Autowired
  private UserRepository userRepository;

  public List<User> findAll() {
    return (List<User>) userRepository.findAll();
  }

  public User addUser(User user) {
    userRepository.save(user);
    return user;
  }
}

Repository

public interface UserRepository extends CrudRepository<User, Integer> {
  // TODO
}

SQL

CREATE TABLE users(
    id INT PRIMARY KEY NOT NULL,
    email   TEXT NOT NULL,
    password    CHAR(20)    NOT NULL
);

Please, somebody help me, because I don't know how to tackle this issue.

Solution

I found the solution. I need to change the script for these one:

CREATE TABLE users(
    id  SERIAL PRIMARY KEY NOT NULL,
    email   TEXT NOT NULL,
    password    TEXT    NOT NULL
);

Then, the Entity should be annotated with this:

@Entity
@Table(name = "users")
public class User {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  @Column(columnDefinition = "serial")
  private Long id;
  private String email;
  private String password;

  public User() {}

  public Long getId() {
    return id;
  }

  public void setId(Long id) {
    this.id = id;
  }

  public String getEmail() {
    return email;
  }

  public void setEmail(String email) {
    this.email = email;
  }

  public String getPassword() {
    return password;
  }

  public void setPassword(String password) {
    this.password = password;
  }
}