[Spring] Spring Data JPA

Previouly we need to define a DAO interface and a DAO impl for 'Employee', it is not so reuseable, since all the DAO has the same structure:

package com.luv2code.springboot.cruddemo.dao;

import com.luv2code.springboot.cruddemo.entity.Employee;
import java.util.List;

public interface EmployeeDAO {
    public List<Employee> findAll();

    public Employee findById (int theId);

    public void save(Employee theEmployee);

    public void deleteById(int theId);
}

Spring data jpa provids a much simple and reuseable way to do the stuff, we only need to info JPA with 'Employee' entity class and its primary id type. Then JPA will provides us all the methods we need, such ass 'findAll' & 'findById' & 'save' & 'deleteById':

package com.luv2code.springboot.cruddemo.dao;

        import com.luv2code.springboot.cruddemo.entity.Employee;
        import org.springframework.data.jpa.repository.JpaRepository;

public interface EmployeeRepository extends JpaRepository<Employee, Integer> {
    // NO need to write any code here
}

We just need to update the service to use new Data JPA:

package com.luv2code.springboot.cruddemo.service;

import com.luv2code.springboot.cruddemo.dao.EmployeeRepository;
import com.luv2code.springboot.cruddemo.entity.Employee;
import org.springframework.beans.factory.annotation.Autowired;

import java.util.Optional;

public class EmployeeServiceImpl implements EmployeeService{

    private EmployeeRepository employeeRepository;

    @Autowired
    public EmployeeServiceImpl (EmployeeRepository theEmployeeRepository) {
        employeeRepository = theEmployeeRepository;
    }

    @Override
    public List<Employee> findAll() {
        return employeeRepository.findAll();
    }

    @Override
    public Employee findById(int theId) {

        Optional<Employee> result=  employeeRepository.findById(theId);
        Employee theEmployee = null;
        if (result.isPresent()) {
            theEmployee = result.get();
        } else {
            throw new RuntimeException("Did not find employee id  - " + theId);
        }

        return theEmployee;
    }

    @Override
    public void save(Employee theEmployee) {
        employeeRepository.save(theEmployee);
    }

    @Override
    public void deleteById(int theId) {
        employeeRepository.deleteById(theId);
    }
}