Spring Boot Rest接口如何正确划分业务层和数据层

Question

I am working with Spring Boot for quite some time now but have surprinsingly not encountered this type of problem before.

Given the following Code example:

Parent

@Entity
@Table(name="Parent")
@Cacheable(true)
@OptimisticLocking(type= OptimisticLockType.VERSION)
@DynamicUpdate

public class Parent implements Serializable {

   private Long id;
   private Child child;

   @Id
   public Long getId() {
     return this.id;
   }

   @ManyToOne(fetch = FetchType.EAGER)
   @JoinColumn(name = "child")
   public Child getChild(){
     return this.child;
   }
}

Child

@Entity
@Table(name="Child")
@Cacheable(true)
@OptimisticLocking(type= OptimisticLockType.VERSION)
@DynamicUpdate

public class Child implements Serializable {

   private Long id;
   private String name;

   @Id
   public Long getId() {
     return this.id;
   }

   public String getName() {
     return this.name;
   }

Repository

@Repository
public interface ParentRepository extends JpaRepository<Parent, Long> {}

Controller

@RestController
public class RestController {

@Autowired
private ParentRepository parentRepository;


@RequestMapping(value="/data/parent/{parentid}", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
public Optional<Parent> getParent(@PathVariable("parentid") Long parentId){
   return parentRepository.findById(parentId);
}

@RequestMapping(value = "/data/parent", method = RequestMethod.POST, produces = MediaType.APPLICATION_JSON_VALUE)
public Parent addParent(@RequestBody Parent parent) {
   return parentRepository.save(parent);   
}

The above code works fine and as expected when executing the GET method. A result would look something like:

{
  "id":1,
  "child": {
    "id":1,
    "name":"Jesus"
}
}

However, The way I need to use the POST method is to pass only the foreign key of the children that I want to connect to my parent. I do not want to create a whole Child Object, serialize it into JSON and add it to the request body. Meaning I want to be able to POST a Parent object with a JSON like this:

{
  "id":1,
  "child":1
}

and let the Rest Interface to the job of fetching my Child object.

I was able to find a way to achieve this by adding another variable

@Transient
Long childId;

to my Parent object and then in the controller, GET the corresponding Child object first and add it to the Parent before persisting.

However, I am quite certain that this is not a good way to solve this problem and that the solution will include dividing my data model into two seperate layers. Unfortunately, I have not yet been able to find out how to do this exactly.

I am thankful for any advise.

Answer 1

You should divide your business model by layers : DTO (used for data exchanging with your REST clients) and Entities (for database operations).

With that seperation you have more flexibility and can POST what you want without messing your entities with stuff like @JsonIgnore or @Transient .

You will have something like:

@PostMapping(value = "/data/parent")
public ParentDTO addParent(@RequestBody LightParentDTO parentDTO) {
   return service.save(parentDTO);   
}

and

class LightParentDTO {
  long parentId;
  long childId;
}

Note that I introduce a service.save(...) , there you can do all your DTO to Entity conversion operations.

Answer 2

If I got you right, what you need to do is use the @jsonignore annotation Try this:

@Entity
@Table(name="Parent")
@Cacheable(true)
@OptimisticLocking(type= OptimisticLockType.VERSION)
@DynamicUpdate

public class Parent implements Serializable {

   private Long id;
   @JsonIgnore     <========================================================
   private Child child;

   @Id
   public Long getId() {
     return this.id;
   }

   @ManyToOne(fetch = FetchType.EAGER)
   @JoinColumn(name = "child")
   public Child getChild(){
     return this.child;
   }
}

let me know if it works