How to save List of objects in Postgres in springboot application

Question

I am working on a springboot application.
I am trying to save a list of custom objects in one of the column, but I am getting ERROR: relation doesn't exist exception on one column

EMPLOYEE DTO:

public class Employee {
private Integer employeeId;
private String employeeName;
private List<Address> addresses;
public Integer getEmployeeId() {
 return employeeId;
}
public void setEmployeeId(Integer employeeId) {
 this.employeeId = employeeId;
}
public String getEmployeeName() {
 return employeeName;
}
public void setEmployeeName(String employeeName) {
 this.employeeName = employeeName;
}
public List<Address> getAddresses() {
 return addresses;
}
public void setAddresses(List<Address> addresses) {
 this.addresses = addresses;
}
}

ADDRESS DTO:

public class Address {
private String state;
private String country;
public String getState() {
 return state;
}
public void setState(String state) {
 this.state = state;
}
public String getCountry() {
 return country;
}
public void setCountry(String country) {
 this.country = country;
}
public Address(String state, String country) {
 super();
 this.state = state;
 this.country = country;
}
public Address() {
}
}

Employee Service:

@Service
public class EmployeeService {
@Autowired
private UserRepository userRepository;
public void persist() {
 Employee employee = new Employee();
 employee.setEmployeeId(1001);
 employee.setEmployeeName("John Doe");
 employee.setAddresses(Arrays.asList(new Address("state_name", "country_name")));
 userRepository.save(employee);
}
}

Data type of address is text in Postgres.

While executing my code, I am getting the below Exception:
org.postgresql.util.PSQLException: ERROR: relation "employee_address" does not exist.

• Apophis: Try with annotations like oneToMany and ManyToOne like the solution here
• mayank bisht: My Address DTO is not a table, it's a plain POJO.

Answer 1

Does UserRepository extend org.springframework.data.repository.CrudRepository? If so... Spring repositories can't operate with plain DTO. Spring repositories can save only entities (class should be annotated with @Entity).

So, you can annotate Employee and Address classes with @Entity. In this case you also need to use @OneToMany for Employee#addresses. You also need to specify @Id property.

 @Entity
 public class Employee {
 @Id
 @GeneratedValue(strategy = GenerationType.AUTO)
 private Integer id;
 private Integer employeeId;
 private String employeeName;
 @OneToMany
 private List<Address> addresses;
 // getters + setters + eq/hc
 }
 @Entity
 public class Address {
 @Id
 @GeneratedValue(strategy = GenerationType.AUTO)
 private Integer id;
 private String state;
 private String country;
 // getters + setters + eq/hc
 }

You can find an example in the following guide: https://spring.io/guides/gs/accessing-data-jpa/

• mayank bisht: Thanks for the answer. Address class is just a DTO, it's not an entity.

Answer 2

You can use @ElementCollection above List<Address> addresses and @Embeddable on Address DTO.