Java Spring 初始化一次 hibernate 存储库

Question

我关注了官方spring tutorial我声明我的对象如下:

存储库:

@Repository
public interface PropertyRepository extends CrudRepository<Property, Long> {
}

属性对象:

@Entity
@Table(catalog = "configdb", name = "properties", uniqueConstraints = {@UniqueConstraint(columnNames = {"property_id"})})
public class Property implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "property_id")
    private Long propertyId;
    @Column(name = "property_key", length = 50)
    private String propertyKey;

应用:

@SpringBootApplication
@ComponentScan({"org.demo*"})

@EnableAutoConfiguration
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);

    }

还有一个非常短的 Controller :

@Controller
@RequestMapping(path = "/demo")
public class PropertyController {
    @Autowired
    private PropertyDao propDao;
    public PropertyController(PropertyRepository repo) {
        propDao = PropertyDao.setRepository(repo);
    }
    @GetMapping(path = "/map")
    public @ResponseBody
    HashMap<String,String> get() {
        return propDao.getPropertiesMap();
    }

PropertyDao 在构造函数中设置其 Repository，然后将 Property 转换为 HashMap。

我从日志中看到，每次在 Controller 上执行请求时，都会调用 Hibernate 并执行对 mysql 的查询，就像在每次请求时创建 PropertyController 一样。

但是这个 Property 对象仅包含缩写配置，并且在每个请求时调用数据库是一个巨大的开销。

你有什么解决办法吗？

编辑:添加PropertyDao

@Component
public class PropertyDao {
    public PropertyDao setRepository(PropertyRepository repository) {...}
    public HashMap<String, String> getPropertiesMap(){...}
}

Answer 1

创建一个服务(服务是单例的，它们仅创建一次)并将逻辑移至那里。然后从 Controller 调用服务方法。

类似这样的事情:

@Service
@Transactional
public class MyService {

    @Autowired
    private PropertyDao propDao;

    public MyService(PropertyRepository repo) {
        propDao = PropertyDao.setRepository(repo);
    }


    HashMap<String,String> getPropertiesMap() {
        return propDao.getPropertiesMap();
    }
}

在你的 Controller 中:

@Controller
@RequestMapping(path = "/demo")
public class PropertyController {
    @Autowired
    private MyService myService;

    public PropertyController(MyService myService) {
        this.myService = myService;
    }

    @GetMapping(path = "/map")
    public @ResponseBody
    HashMap<String,String> get() {
        return myService.getPropertiesMap();
    }
}