public class WebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {

    @Override
    protected Class<?>[] getRootConfigClasses() {
        return new Class<?>[]{AppConfiguration.class};
    }

    @Override
    protected Class<?>[] getServletConfigClasses() {
        return new Class[]{WebConfiguration.class};
    }

    @Override
    protected String[] getServletMappings() {
        return new String[]{"/"};
    }
}

@Configuration
@EnableJpaRepositories
@EnableTransactionManagement
public class AppConfiguration {

    @Bean
    public DataSource dataSource() {
        EmbeddedDatabaseBuilder builder = new EmbeddedDatabaseBuilder();
        return builder.setType(EmbeddedDatabaseType.HSQL).build();
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
        HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        vendorAdapter.setDatabase(Database.HSQL);
        vendorAdapter.setGenerateDdl(true);

        LocalContainerEntityManagerFactoryBean factory = new LocalContainerEntityManagerFactoryBean();
        factory.setJpaVendorAdapter(vendorAdapter);
        factory.setPackagesToScan(getClass().getPackage().getName());
        factory.setDataSource(dataSource());

        return factory;
    }

    @Bean
    public PlatformTransactionManager transactionManager() {
        return new JpaTransactionManager();
    }
}

@Configuration
public class WebConfiguration extends RepositoryRestMvcConfiguration {
}

@Entity
public class Book {

    @Id
    private String isbn;

    private String title;

    private String language;

    @ManyToMany
    private List<Author> authors;

}

@Entity
public class Author {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    private Integer id;

    private String name;

    @ManyToMany(mappedBy = "authors")
    private List<Book> books;

}

@RestResource(path = "books", rel = "books")
public interface BookRepository extends PagingAndSortingRepository<Book, Long> {
}

@RestResource(path = "authors", rel = "authors")
public interface AuthorRepository extends PagingAndSortingRepository<Author, Integer> {
}

{
  "links" : [ {
    "rel" : "books",
    "href" : "http://localhost:8080/books"
  }, {
    "rel" : "authors",
    "href" : "http://localhost:8080/authors"
  } ],
  "content" : [ ]
}

{"name":"Uncle Bob"}

{
  "title": "Clean Code",
  "authors": [
      {
          "rel": "authors",
          "href": "http://localhost:8080/authors/1"
      }
  ]
}

{
  "links" : [ ],
  "content" : [ {
    "links" : [ {
      "rel" : "books.Book.authors",
      "href" : "http://localhost:8080/books/0132350882/authors"
    }, {
      "rel" : "self",
      "href" : "http://localhost:8080/books/0132350882"
    } ],
    "title" : "Clean Code"
  } ],
  "page" : {
    "size" : 20,
    "totalElements" : 1,
    "totalPages" : 1,
    "number" : 1
  }
}

public class BookApiIT {

    private final RestTemplate restTemplate = new RestTemplate();

    private final String authorsUrl = "http://localhost:8080/authors";
    private final String booksUrl = "http://localhost:8080/books";

    @Test
    public void testCreateBookWithAuthor() throws Exception {
        final URI authorUri = restTemplate.postForLocation(authorsUrl, sampleAuthor()); // create Author

        final URI bookUri = new URI(booksUrl + "/" + sampleBookIsbn);
        restTemplate.put(bookUri, sampleBook(authorUri.toString())); // create Book linked to Author

        Resource<Book> book = getBook(bookUri);
        assertNotNull(book);

        final URI authorsOfBookUri = new URI(book.getLink("books.Book.authors").getHref());
        Resource<List<Resource<Author>>> authors = getAuthors(authorsOfBookUri);
        assertNotNull(authors.getContent());
        assertFalse(authors.getContent().isEmpty()); // check if /books/0132350882/authors contains an author
    }

    private String sampleAuthor() {
        return "{\"name\":\"Robert C. Martin\"}";
    }

    private final String sampleBookIsbn = "0132350882";

    private String sampleBook(String authorUrl) {
        return "{\"title\":\"Clean Code\",\"authors\":[{\"rel\":\"authors\",\"href\":\"" + authorUrl + "\"}]}";
    }

    private Resource<Book> getBook(URI uri) {
        return restTemplate.exchange(uri, HttpMethod.GET, null, new ParameterizedTypeReference<Resource<Book>>() {
        }).getBody();
    }

    private Resource<List<Resource<Author>>> getAuthors(URI uri) {
        return restTemplate.exchange(uri, HttpMethod.GET, null, new ParameterizedTypeReference<Resource<List<Resource<Author>>>>() {
        }).getBody();
    }
}

@Controller
@RequestMapping(value = "/bookcase")
public class BookCaseController {

    private BookCase bookCase;

    @RequestMapping(method = RequestMethod.GET)
    @ResponseBody
    public BookCase getBookCase() {
        return this.bookCase;
    }

    @RequestMapping(method = RequestMethod.PUT)
    @ResponseStatus(HttpStatus.NO_CONTENT)
    public void setBookCase(@RequestBody BookCase bookCase) {
        this.bookCase = bookCase;
    }

}

@Configuration
@EnableWebMvc
@ComponentScan
public class WebConfiguration extends WebMvcConfigurerAdapter {

    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> httpMessageConverters) {
        httpMessageConverters.add(new BookCaseMessageConverter(new MediaType("text", "csv")));
    }
}

public class Book {

    private String isbn;

    private String title;

    public Book(String isbn, String title) {
        this.isbn = isbn;
        this.title = title;
    }

    // ...
}

public class BookCase extends ArrayList<Book> {

    public BookCase() {
    }

    public BookCase(Collection<? extends Book> c) {
        super(c);
    }
}

public class BookCaseMessageConverter extends AbstractHttpMessageConverter<BookCase> {

    public BookCaseMessageConverter() {
    }

    public BookCaseMessageConverter(MediaType supportedMediaType) {
        super(supportedMediaType);
    }

    public BookCaseMessageConverter(MediaType... supportedMediaTypes) {
        super(supportedMediaTypes);
    }

    @Override
    protected boolean supports(Class<?> clazz) {
        return BookCase.class.equals(clazz);
    }

    @Override
    protected BookCase readInternal(Class<? extends BookCase> clazz, HttpInputMessage httpInputMessage) throws IOException, HttpMessageNotReadableException {
        CSVReader reader = new CSVReader(new InputStreamReader(httpInputMessage.getBody()));
        List<String[]> rows = reader.readAll();
        BookCase bookCase = new BookCase();
        for (String[] row : rows) {
            bookCase.add(new Book(row[0], row[1]));
        }
        return bookCase;
    }

    @Override
    protected void writeInternal(BookCase books, HttpOutputMessage httpOutputMessage) throws IOException, HttpMessageNotWritableException {
        CSVWriter writer = new CSVWriter(new OutputStreamWriter(httpOutputMessage.getBody()));
        for (Book book : books) {
            writer.writeNext(new String[]{book.getIsbn(), book.getTitle()});
        }
        writer.close();
    }
}