Multiple JPA Repositories with multiple Entity Mapping conflict - spring-boot

Question

I am creating a simple one to many relationship using JPA and Spring Data Rest. But i am getting this error
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'designationRepository' defined in com.example.relational.BootRelations.repository.DesignationRepository defined in #EnableJpaRepositories declared on JpaRepositoriesRegistrar.EnableJpaRepositoriesConfiguration: Cannot resolve reference to bean 'jpaMappingContext' while setting bean property 'mappingContext'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jpaMappingContext': Invocation of init method failed; nested exception is org.hibernate.AnnotationException: No identifier specified for entity: com.example.relational.BootRelations.models.Designation
That is because I have #Entity classes like Designation and Employee, the code follows like:
#Entity
public class Designation {
private String Designation;
private float Salary;
#OneToMany(targetEntity=Employee.class, mappedBy="designation", fetch=FetchType.LAZY, cascade=CascadeType.ALL)
#JoinColumn(name="Emp_Id")
private Set<Employee> employee;
// Getter & Setter and Constructors
}
Now Employee class:
#Entity
#Table(name="Employee")
public class Employee {
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
#Column(name="Emp_Id")
private int Emp_Id;
#Column(name="Emp_Name")
private String Emp_Name;
#Column(name="Emp_Email")
private String Emp_Email;
#OneToOne(targetEntity=Designation.class, mappedBy="employee", fetch=FetchType.LAZY, cascade=CascadeType.ALL)
private Designation designation;
// // Getter & Setter and Constructors
}
The repositories are:
public interface DesignationRepository extends JpaRepository<Designation, Integer> {}
public interface EmployeeRepository extends JpaRepository<Employee, Integer> {}
Services:
#Service
public class DesignationServiceImpl implements DesignationService {
private DesignationRepository designationRepository;
#Autowired
public DesignationServiceImpl(DesignationRepository designationRepository) {
this.designationRepository = designationRepository;
}
#Override
public List<Designation> findAllDesignation() {
return designationRepository.findAll();
}
}
public class EmployeeServiceImpl implements EmployeeService {
private EmployeeRepository employeeRepository;
#Autowired
public EmployeeServiceImpl(#Qualifier("employeeJPAImpl") EmployeeRepository employeeRepository) {
this.employeeRepository = employeeRepository;
}
}
#Service
public class DesignationServiceImpl implements DesignationService {
private DesignationRepository designationRepository;
#Autowired
public DesignationServiceImpl(#Qualifier("DesignationRepository") DesignationRepository designationRepository) {
this.designationRepository = designationRepository;
}
#Override
public List<Designation> findAllDesignation() {
return designationRepository.findAll();
}
}
As I had two entities I had two controllers:
#RestController
#RequestMapping("/api")
public class DesignationController {
private DesignationService designationService;
#Autowired
public DesignationController(DesignationService designationService) {
this.designationService = designationService;
}
#GetMapping("/designation")
public List<Designation> getAllDesignation(){
return designationService.findAllDesignation();
}
}
and
#RestController
#RequestMapping("/api")
public class EmployeeController {
private EmployeeService employeeService;
#Autowired
public EmployeeController(EmployeeService employeeService) {
this.employeeService = employeeService;
}
// Mappings
}
Can anyone help me solve this issue? Until I had one entity it was working fine; as soon as I added another one it failed to start, with the error. Please help me fix the issue.

Answer 1

In Employee class make this changes.
#Entity
#Table
public class Employee {
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
#Column
private Long empId;
#Column
private String Name;
#Column
private String Email;
#OneToMany(targetEntity=Designation.class, fetch=FetchType.LAZY, cascade=CascadeType.ALL)
private Designation designation;
// // Getter & Setter and Constructors
}
In the Designation class, make this changes..
#Entity
public class Designation {
#Id
private Long id;
private String role;
private float salary;
#ManyToOne(targetEntity=Employee.class, fetch=FetchType.LAZY, cascade=CascadeType.ALL)
#JoinColumn
private Set<Employee> employee;
// Getter & Setter and Constructors
}
This will result in a table structure like this.
Employee
EMP_ID
NAME
EMAIL
Designation
ID
ROLE
SALARY
EMPLOYEE_ID
In OneToMany and ManyToOne association, we must keep a note that, which class is holding the Many side. That side is known as the owning side. As that class will contain the foreign key. Here, our designation class is containing the Many side. So, it will create a foreign key automatically.
If we give the #JoinColumn in the Employee class. Still we will get the Designation class as the Owning class.
You can refer this article, for more details.
Rather than this, let me tell you some of your major mistakes.
Do not give the variables name same as your class name.
By writing variables name as empId in java file, it will result EMP_ID in database.
If a column name or a table name is same your variable name, you can avoid re-mentioning it.
means, if my entity class name is Employee. And I want my database Table name should also be EMPLOYEE. I can avoid specifying #Table(name="EMPLOYEE").
I hope it would be helpful !!