Hibernate with Spring Boot

Hibernate ORM handles object-relational impedance mismatch problems by replacing direct, persistent database accesses with high-level object handling functions. https://howtodoinjava.com/spring-boot2/spring-boot-crud-hibernate/

Vulgarization

Dependencies

pom.xml file

org.springframework.boot.spring-boot-starter-web
org.springframework.boot.spring-boot-starter-data-jpa
com.h2database.h2

Entity

<source lang="java">

@Entity
@Table(name="TABLE_EMPLOYEE")
public class EmployeeEntity{
   @Id
   @GeneratedValue
   private Long id;
   @Column(name="column_name", nullable=false, length=200)
   @Override
   public String toString() { ... }
}

</source>

Repository

See the differences of : JpaRepository = PagingAndSortingRepository + CrudRepository here ==>> thumb|100px|JpaRepository <source lang="java">

@Repository
public interface EmployeeRepository 
   extends JpaRepository<EmployeeEntity, Long> { 
   ...
}

</source>

Datasource Configuration

application.properties
#Required
spring.datasource.url=jdbc:h2:file:~/test
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=user
spring.datasource.password=password

#Optionnal
# Enabling H2 Console
spring.h2.console.enabled=true
# Custom H2 Console URL
spring.h2.console.path=/h2-console

# create database schema from SQL files
spring.jpa.hibernate.ddl-auto=none
#Turn Statistics on and log SQL stmts
spring.jpa.show-sql=true
spring.jpa.properties.hibernate.format_sql=true
spring.jpa.properties.hibernate.generate_statistics=false 
#logging.level.org.hibernate.type=trace
#logging.level.org.hibernate.stat=debug
logging.pattern.console=%d{yyyy-MM-dd HH:mm:ss} - %msg%n

Service

<source lang="java">

@Service
public class EmployeeService {    
   @Autowired
   TableNameRepository repository;
   
   /********** Get All **********/
   public List<EmployeeEntity> getAllEmployees(){
       List<EmployeeEntity> employeeList = repository.findAll();
        
       if(employeeList.size() > 0) {
           return employeeList;
       } else {
           return new ArrayList<EmployeeEntity>();
       }
   }

   /********** Get **********/
   public EmployeeEntity getEmployeeById(Long id) throws RecordNotFoundException{
       Optional<EmployeeEntity> employee = repository.findById(id);
        
       if(employee.isPresent()) {
           return employee.get();
       } else {
           throw new RecordNotFoundException("No employee record exist for given id");
       }
   }

   /********** Create or Update **********/
   public EmployeeEntity createOrUpdateEmployee(EmployeeEntity entity) throws RecordNotFoundException{
       Optional<EmployeeEntity> employee = 'repository.findById(entity.getId());
        
       if(employee.isPresent()){
           EmployeeEntity newEntity = employee.get();
           newEntity.setEmail(entity.getEmail());
           newEntity.setFirstName(entity.getFirstName());
           newEntity.setLastName(entity.getLastName());

           newEntity = repository.save(newEntity);
            
           return newEntity;
       } else {
           entity = repository.save(entity);
            
           return entity;
       }
   }    

   /********** Delete **********/
   public void deleteEmployeeById(Long id) throws RecordNotFoundException{
       Optional<EmployeeEntity> employee = repository.findById(id);
        
       if(employee.isPresent()){
           repository.deleteById(id);
       } else {
           throw new RecordNotFoundException("No employee record exist for given id");
       }
   }
}

</source>

Controller (REST)

<source lang="java">

@RestController
@RequestMapping("/employees")
public class EmployeeController{
   @Autowired
   EmployeeService service;

   @GetMapping
   public ResponseEntity<List<EmployeeEntity>> getAllEmployees(){
       List<EmployeeEntity> list = service.getAllEmployees();

       return new ResponseEntity<List<EmployeeEntity>>(list, new HttpHeaders(), HttpStatus.OK);
   }

   @GetMapping("/{id}")
   public ResponseEntity<EmployeeEntity> getEmployeeById(@PathVariable("id") Long id) throws RecordNotFoundException {
       EmployeeEntity entity = service.getEmployeeById(id);

       return new ResponseEntity<EmployeeEntity>(entity, new HttpHeaders(), HttpStatus.OK);
   }

   @PostMapping
   public ResponseEntity<EmployeeEntity> createOrUpdateEmployee(EmployeeEntity employee) 
throws RecordNotFoundException {
       EmployeeEntity updated = service.createOrUpdateEmployee(employee);
       return new ResponseEntity<EmployeeEntity>(updated, new HttpHeaders(), HttpStatus.OK);
   }

   @DeleteMapping("/{id}")
   public HttpStatus deleteEmployeeById(@PathVariable("id") Long id) throws RecordNotFoundException {
       service.deleteEmployeeById(id);
       return HttpStatus.FORBIDDEN;
   }
}

</source>

Exceptions

<source lang="java">

@ResponseStatus(value = HttpStatus.NOT_FOUND)
public class RecordNotFoundException extends Exception {
 
   private static final long serialVersionUID = 1L;
    
   public RecordNotFoundException(String message) {
       super(message);
   }
    
   public RecordNotFoundException(String message, Throwable t) {
       super(message, t);
   }
}

</source>