Spring Framework Responses from POST - spring

What is the standard object design for accepting a POST request from a client, saving the record to the database, and then returning a response back to the client? I'm working with the Spring framework.
Should I be sending back the entity and hiding properties that aren't necessary for the response?
#RestController
public class SomeController {
private final SomeService service;
#PostMapping(value = "/post/new", produces = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<SomeEntity> post(#RequestBody final SomeEntity someEntity) {
SomeEntity savedEntity = service.save(someEntity);
return ResponseEntity.ok(savedEntity);
}
}
#Entity
#Table(name = "posts")
public class SomeEntity {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(name = "title")
private String title;
#Column(name = "body")
#JsonIgnore
private String body;
#JsonIgnore
#Column(name = "deleted_ind")
private boolean deleted;
#JsonIgnore
#Column(name = "author")
private String author;
#Column(name = "created_at")
private LocalDateTime createdAt;
}
or would I accept some sort of POST request object that I convert to an entity, then re-assemble the entity into a response?
#JsonIgnoreProperties(ignoreUnknown = true)
public class SomePostRequestResource {
private String title;
private String body;
private String createdAt;
}
#RequiredArgsConstructor
#RestController
public class SomeController {
private final SomeService service;
private final SomeResourceAssembler resourceAssembler;
#PostMapping(value = "/post/new", produces = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<SomePostRequestResource> post(
#RequestBody final SomePostRequestResource someResource
) {
SomeEntity savedEntity = service.convertToEntityAndSave(someResource);
SomePostRequestResource response = resourceAssembler.toResource(savedEntity);
return ResponseEntity.ok(response);
}
}
But then maybe I only want to send back the createdAt, would I hide the other properties in the SomePostRequestResource, or do I need another object to represent the response, which only has the property I want to send back?
I would also appreciate any book or article suggestions related to desigining objects for use with a RESTful API. I have seen articles concerning how to design and name the endpoints, but not so many concerning how to design the objects on the backend.

I would recommend you create a DTO class for the incoming/outgoing data containing the filed that are set/viewable by the client like:
public class SomeEntityIncomingDto {
private String title;
....
}
public class SomeEntityOutgoingDto {
private Long id;
private String title;
....
}
On the other hand, You won't need to map your persistence entities to DTOs and vice versa manually, you can use a library like ModelMapper or MapStruct that handles the conversion automatically.

Related

Infinite recursion with #JsonManagedReference and #JsonBackReference

I have an entity class that is self referencing itself. For example, a document can be linked to a parent document.
#Entity
#Table(name = "documents")
public class DocumentEntity {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#JsonIgnore
#JsonManagedReference
#ManyToOne(fetch = FetchType.LAZY)
private DocumentEntity parentDocument;
#JsonBackReference
#OneToMany(mappedBy = "parentDocument", fetch = FetchType.LAZY)
private Set<DocumentEntity> documents;
#Column(nullable = false, unique = true)
private String documentId;
#Column(nullable = false)
private String fileName;
}
In my entry point / controller layer :
#GetMapping(
path = "/{fileId}",
produces = { MediaType.APPLICATION_JSON_VALUE, MediaType.APPLICATION_XML_VALUE }
)
public DocumentResponse getParentDocument(#PathVariable("fileId") String fileId) {
modelMapper = createModelMapper();
DocumentDto documentDto = documentService.getParentDocument(fileId);
DocumentResponse documentResponse = modelMapper.map(documentDto, DocumentResponse.class);
documentResponse.getDocuments().forEach(document -> System.out.println(document.getDocumentId()));
return documentResponse;
}
In my Service layer :
#Override
public DocumentDto getParentDocument(String documentId) {
DocumentDto documentDtoResponse = new DocumentDto();
ModelMapper modelMapper = new ModelMapper();
modelMapper.getConfiguration().setMatchingStrategy(MatchingStrategies.STRICT);
DocumentEntity storedDocumentEntity =
documentRepository.findByDocumentIdAndParentDocumentNull(documentId);
if(storedDocumentEntity.getDocumentId().isEmpty() || storedDocumentEntity.getDocumentId().isBlank()) {
throw new AppFileNotFoundException("Oops file not found");
}
documentDtoResponse = modelMapper.map(storedDocumentEntity, DocumentDto.class);
return documentDtoResponse;
}
In the repository:
Now I'm making a sql request in a repository interface that extends JpaRepository.
The application allow to have a parent document with child documents and child documents cannot have child documents.
#Repository
public interface DocumentRepository extends JpaRepository<DocumentEntity, Long> {
DocumentEntity findByDocumentIdAndParentDocumentNull(String documentId);
}
I also tried to implement the method using JPQL :
#Query("SELECT d FROM DocumentEntity d WHERE d.documentId = :documentId AND d.parentDocument IS NULL")
DocumentEntity findByDocumentIdAndParentDocumentNull(String documentId);
This query allow to get parent documents and child documents.
My code implementation separates response and database by using a DTO layer.
Issue:
My issue is that I obtain an infinite recursion. I think i'm using #JsonManagedReference and #JsonBackReference correctly. Even adding the same annotations to DTO pojo do not solve issue. If i add those annotation to response POJO, then I do not obtain child documents.
Could not write JSON: Infinite recursion (StackOverflowError); nested exception is com.fasterxml.jackson.databind.JsonMappingException
Inially I have a DTO class that also self refers to itself.
public class DocumentDto implements Serializable {
private String filePath;
private String mimeType;
private String documentType;
private DocumentDto parentDocument;
Set<DocumentDto> documents;
}
I created a second class without properties that are causing problems;
public class DocumentChildDto implements Serializable {
private String filePath;
private String mimeType;
private String documentType;
}
In the DocumentDto I simply replaced the DocumentDto with DocumentChildDto.
public class DocumentDto implements Serializable {
private String filePath;
private String mimeType;
private String documentType;
private DocumentChildDto parentDocument;
Set<DocumentChildDto> documents;
}
It's more a hack than a technical solution but it works fine. Here childDocumentDto object won't load the parentDocument.

How to post an Image and JSON object with single request to back end Spring Boot

I want to send image and JSON data to my back end in Spring Boot.
This is my method:
#PostMapping
public void uploadFile(#ModelAttribute FileUploadDto fileUploadDto) {
My FileUploadDto model:
public class FileUploadDto {
private MultipartFile file;
private CategoryModel category;
My CategoryModel model:
#Entity
#Table(name = "Category")
#JsonIgnoreProperties({ "hibernateLazyInitializer", "handler" })
public class CategoryModel {
#Id
#Column(name = "id")
//#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String category_name;
private String category_description;
private String image_path;
#JsonIgnore
#OneToMany( mappedBy = "category")
private Set<ProductModel> category;
I do not understand where I'm wrong.
My postman request:
Your payload has to be raw and in json form. Something like this would help Spring boot to convert your payload into a object of an example class:
public class Foo{
public String foo;
public String foo1;
//Getters setters
}
And the request handling method:
#PostMapping
public void uploadFile(#RequestBody Foo foo)
It is also recommended to parse the payload into some a temporary class and then convert objects of the temporary class into the Entity class and vice versa. Take a look at: https://struberg.wordpress.com/2012/01/08/jpa-enhancement-done-right/ for more information
Also, if you want to upload file per REST I also recommend you to take a look at the following documentation: https://www.callicoder.com/spring-boot-file-upload-download-rest-api-example/
Best luck.

SPRING REST controller - return image AND json values

I have built a rest web service, using SPRING and Hibernate.
I have 2 entities : Image and user, linked with a oneToOne annotation.
When I try to return the user details AND the image corresponding to this user, I get this error :
"org.springframework.web.HttpMediaTypeNotAcceptableException: Could not find acceptable representation"
When I do it separately It works fine, but when I do it in one route, I get this error.
Here is my controller :
#CrossOrigin(
origins = "*",
methods = {RequestMethod.POST, RequestMethod.GET, RequestMethod.OPTIONS, RequestMethod.DELETE},
allowedHeaders = "*")
#RestController
#RequestMapping(path = "/user")
public class UserController {
#Autowired
UserRepository userRepository;
#Autowired
ImageRepository imageRepsository;
doesn't work--> #RequestMapping(value="/{userId}/getUserAndImage",method=RequestMethod.GET,produces = MediaType.IMAGE_JPEG_VALUE )
public Optional<User> getUserAndImage(#PathVariable Long userId) {
return userRepository.findById(userId);
}
works fine--> #RequestMapping(value="/{userId}/image", method=RequestMethod.GET, produces = MediaType.IMAGE_PNG_VALUE)
public byte[] getUserImage(#PathVariable Long userId) {
byte[] image = (imageRepsository.findImageWithUserId(userId)).getImage();
return image;
}
Here are entities :
User entity :
#Entity
#Table(name="users")
public class User {
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
private Long id;
#NotNull
#Size(max=100)
#Column
private String nom;
#NotNull
#Size(max=250)
#Column
private String prenom;
#OneToOne(fetch=FetchType.EAGER,
cascade = CascadeType.PERSIST)
private Image image;
//getters and setters
}
Image entity :
#Entity
#Table(name="images")
public class Image {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(name="image")
#Lob
private byte[] image;
#OneToOne(fetch = FetchType.EAGER)
#JoinColumn(name="user_id")
private User user;
//getters and setters
}
in the annotation, produce set as MediaType.IMAGE_JPEG_VALUE, then your code return response as User object. As result it throw that exception because spring expect your code to return JPEG type file only.
What can i suggest here,use produces = MediaType.APPLICATION_JSON_VALUE, and convert your image from byte[] to base64 string then return response as json object

Ignoring Nested properties in Jackson OnDemand

I am working on a spring boot application with Hibernate as ORM and Jackson as JSON serialiser .
I have three model objects and CRUD operations for all three models.
Class Student{
private Teacher teacher; // Teacher of the student — to be fetched eagerly
+Getter/Setter
}
class Teacher {
private List<Subject> subject; // List of subjects associated to that user— to be fetched eagerly
+Getter/Setter
}
class Subject {
private long subjectId
//Other subject properties
+ Getter/Setter
}
Whenever I trigger a get request for student info I get the teacher info which is correct where as I also receive Subject info as well which is unnecessary for me. In the same time when I request for Teacher info, I need Subject info should be associated to that for sure. If I use #JsonBackReference for subject I am losing it all the time. I am not sure how to achieve this.
Thanks in advance for your help!!
You can also annotate like this
Class Student{
#JsonIgnoreProperties("subject")
private Teacher teacher; // Teacher of the student — to be fetched eagerly
}
You can use JSON Views
From the spring blog:
public class View {
interface Summary {}
}
public class User {
#JsonView(View.Summary.class)
private Long id;
#JsonView(View.Summary.class)
private String firstname;
#JsonView(View.Summary.class)
private String lastname;
private String email;
private String address;
private String postalCode;
private String city;
private String country;
}
public class Message {
#JsonView(View.Summary.class)
private Long id;
#JsonView(View.Summary.class)
private LocalDate created;
#JsonView(View.Summary.class)
private String title;
#JsonView(View.Summary.class)
private User author;
private List<User> recipients;
private String body;
}
and in the controller
#RestController
public class MessageController {
#Autowired
private MessageService messageService;
#JsonView(View.Summary.class)
#RequestMapping("/")
public List<Message> getAllMessages() {
return messageService.getAll();
}
#RequestMapping("/{id}")
public Message getMessage(#PathVariable Long id) {
return messageService.get(id);
}
}
PS: No link to http://fasterxml.com/ as it's currently down.

Why the record is posted twice in the database?

Can you tell me, why the record is posted twice in the database. I think. this happens because I use save() method. But shouldn't I save the master-entity and dependent-entity separately?
Controller method:
#RequestMapping(value = "/addComment/{topicId}", method = RequestMethod.POST)
public String saveComment(#PathVariable int topicId, #ModelAttribute("newComment")Comment comment, BindingResult result, Model model){
Topic commentedTopic = topicService.findTopicByID(topicId);
commentedTopic.addComment(comment);
// TODO: Add a validator here
if (!comment.isValid() ){
return "//";
}
// Go to the "Show topic" page
commentService.saveComment(comment);
return "redirect:../details/" + topicService.saveTopic(commentedTopic);
}
Services:
#Service
#Transactional
public class CommentService {
#Autowired
private CommentRepository commentRepository;
public int saveComment(Comment comment){
return commentRepository.save(comment).getId();
}
}
#Service
#Transactional
public class TopicService {
#Autowired
private TopicRepository topicRepository;
public int saveTopic(Topic topic){
return topicRepository.save(topic).getId();
}
}
Model:
#Entity
#Table(name = "T_TOPIC")
public class Topic {
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
private int id;
#ManyToOne
#JoinColumn(name="USER_ID")
private User author;
#Enumerated(EnumType.STRING)
private Tag topicTag;
private String name;
private String text;
#OneToMany(fetch = FetchType.EAGER, mappedBy = "topic", cascade = CascadeType.ALL)
private Collection<Comment> comments = new LinkedHashSet<Comment>();
}
#Entity
#Table(name = "T_COMMENT")
public class Comment
{
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
private int id;
#ManyToOne
#JoinColumn(name="TOPIC_ID")
private Topic topic;
#ManyToOne
#JoinColumn(name="USER_ID")
private User author;
private String text;
private Date creationDate;
}
In this concrete case, you do not need to save the master and the client.
Saving the master or the client would be enough (with this concrete mapping)
But I think the main problem is that you do not have a good equals method in your Comment so your ORM Provider think that there are two different comments, and therefore store them twice.

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