Spring REST

Java JSON Data Binding

Also known as:

Mapping
Serialization/Deserialization
Marshalling/Unmarshalling

This is the process to convert JSON to a Java POJO and vice versa. The Jackson Project handles data binding (it is automatically included in Spring Boot Starter Web). It works through attributes and getter/setter methods of Java POJOs.

@RestController

@RestController
@RequestMapping("/api/books")
public class BookController {
    @Autowired
    private Book book;
}

@RestController: Indicates that the class handles REST requests and automatically serializes responses to JSON.
@RequestMapping(“/api/books”): Sets the base URI for all endpoints in the controller.

POST

// **Create a new book**
@PostMapping
public ResponseEntity<Book> createBook(@RequestBody Book book) {
    Book savedBook = bookRepository.save(book);
    return new ResponseEntity<>(savedBook, HttpStatus.CREATED);
}

POST with Created Location

@PostMapping
public ResponseEntity<Book> createBook(@RequestBody Book book) {
    Book savedBook = bookRepository.save(book);
    URI location = ServletUriComponentsBuilder.fromCurrentRequest()
            .path("/{id}")
            .buildAndExpand(savedBook.getId())
            .toUri();
    return ResponseEntity.created(location).build();
}

This response puts the location of the generated entity in the header.
Example: (location: http://localhost:8080/book/8)

GET

// **Get all books**
@GetMapping
public List<Book> getAllBooks() {
    return bookRepository.findAll();
}

// **Get a book by ID**
@GetMapping("/{id}")
public ResponseEntity<Book> getBookById(@PathVariable Long id) {
    Optional<Book> book = bookRepository.findById(id);
    return book.map(value -> ResponseEntity.ok().body(value))
            .orElseGet(() -> ResponseEntity.notFound().build());
}

PUT

// **Update a book**
@PutMapping("/{id}")
public ResponseEntity<Book> updateBook(@PathVariable Long id, @RequestBody Book bookDetails) {
    Optional<Book> optionalBook = bookRepository.findById(id);

    if (optionalBook.isPresent()) {
        Book book = optionalBook.get();
        book.setTitle(bookDetails.getTitle());
        book.setAuthor(bookDetails.getAuthor());
        book.setIsbn(bookDetails.getIsbn());

        Book updatedBook = bookRepository.save(book);
        return ResponseEntity.ok(updatedBook);
    } else {
        return ResponseEntity.notFound().build();
    }
}

DELETE

// **Delete a book**
@DeleteMapping("/{id}")
public ResponseEntity<Void> deleteBook(@PathVariable Long id) {
    Optional<Book> book = bookRepository.findById(id);

    if (book.isPresent()) {
        bookRepository.delete(book.get());
        return ResponseEntity.noContent().build();
    } else {
        return ResponseEntity.notFound().build();
    }
}

Key Annotations

@PathVariable: Extracts values from the URI, e.g., /api/books/1
@RequestBody: Binds the HTTP request body to a transfer or domain object.

Customize Response

Customize field name

@JsonIgnoreProperties("book_id") On pojo/entity

public class Book {
    @JsonProperty("book_id")
    private int id;
    //...
}