声明createEntityManagerFactory的最佳方法

Question

I work actually on a springboot project with JPA. I'm looking for a better implementation, currently it works but I have the impression that it is not the best way

    @RestController
public class inscription {

EntityManagerFactory objFactory = Persistence.createEntityManagerFactory("com.myapplication_jar_0.0.1-SNAPSHOTPU");

 UserJpaController userCtrl = new UserJpaController(objFactory);
 SerialsJpaController licenseCtrl = new SerialsJpaController(objFactory);


   @CrossOrigin(origins = CURRENT_IP)
    @RequestMapping(value = "/createaccount", method = RequestMethod.GET)
    public CreatAccountResponseTemplate createAccount(
            @RequestParam(value = "login") String login,
            @RequestParam(value = "password") String password,
         ) 
    {
        EntityManager manager = objFactory.createEntityManager();

        CreatAccountResponseTemplate responseTemplate = new CreatAccountResponseTemplate();

...}

Answer 1

Spring JPA helps to reduce the boilerplate code that is need in order to configure your data repository.

Maybe using the EntityManagerFactory as a member of your RestController could be a unnecesary dependency. Here is another alternative:

1. Create your domain

The entity

@Entity
public class DataCenter {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private String id;

    private String name;

    private String location;

   .......

}

2. Creates the interface repository in order to handle the database operations related to your Entity.

Repository

public interface DataCenterRepository extends JpaRepository<DataCenter,String> {}

3. Autowired the Repository to your controller, this example is for a standard controller but it also works perfectly for a RestController too.

The Controller

@Controller
@RequestMapping("/datacenters")
public class DataCenterController {

    private final DataCenterRepository dataCentersRepository;

    @Autowired
    public DataCenterController(DataCenterRepository dataCentersRepository){
        this.dataCentersRepository=dataCentersRepository;
    }

@RequestMapping(value = "/save", method=RequestMethod.POST)
public ModelAndView  save(@RequestParam(value="name") String datacenterName,
                          @RequestParam(value="age") String datacenterLocation, ModelAndView  modelAndView ) {
    DataCenter dataCenter = new DataCenter(datacenterName, datacenterLocation);
    dataCentersRepository.save(dataCenter);
    modelAndView.addObject("datacenter", dataCenter);
    modelAndView.setViewName("success");
    return modelAndView;
}

    @RequestMapping(value="/all", method=RequestMethod.GET)
    public String getAll(Model model){
        model.addAttribute("datacenters", dataCentersRepository.findAll());
        return "datacenters";
    }

If you are forced to @Autowired your EntityManagerFactory then just

@Autowired
private EntityManagerFactory entityManagerFactory;

Answer 2

The best way to create EntityManagerFactory in spring boot is to write below configuration in application.properties file.

spring.jpa.show-sql=false
spring.jpa.properties.hibernate.format_sql=false
spring.jpa.hibernate.ddl-auto=update
spring.jpa.database-platform = org.hibernate.dialect.PostgreSQLDialect

spring.datasource.url=jdbc:postgresql://localhost:5432/testdb
spring.datasource.username=postgres
spring.datasource.password=root
spring.datasource.driver-class-name=org.postgresql.Driver

The above configuration uses postgreSQL database. This configuration will automatically create DataSource , EntityManagerFactory and JpaTransactionManager bean and hence simplify database connectivity. Also you can access entityManager object with below code:

   @PersistenceContext
   private EntityManager entityManager;

Useful links:

• https://projects.spring.io/spring-data-jpa/

• https://docs.spring.io/spring-data/jpa/docs/current/reference/html/