Spring Data REST: “no String-argument constructor/factory method to deserialize from String value”

问题

When I use Lombok in my Spring Data REST application to define complex types like:

@NoArgsConstructor
@AllArgsConstructor
@Data

@Entity
@Table(name = "BOOK")
public class Book {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(nullable = false)
    private Long id;

    private String title;

    @ManyToOne(cascade = {CascadeType.DETACH, CascadeType.MERGE, CascadeType.REFRESH})
    private Person author;

    // ...
}

with a Spring Data REST controllers like:

@RepositoryRestController
public class BookRepositoryRestController {

    private final BookRepository repository;

    @Autowired
    public BookRepositoryRestController(BookRepository repository) {
        this.repository = repository;
    }

    @RequestMapping(method = RequestMethod.POST,value = "/books")
    public @ResponseBody PersistentEntityResource post(
        @RequestBody Book book,
        PersistentEntityResourceAssembler assembler) {

        Book entity = processPost(book);

        return assembler.toResource(entity);
    }

    private Book processPost(Book book) {
        // ...
        return this.repository.save(book);
    }
}

I get an ugly error:

no String-argument constructor/factory method to deserialize from String value

from Spring Data REST's use of Jackson with a Book POST like:

curl -X POST 
     -H 'content-type: application/json' 
     -d '{"title":"Skip Like a Pro", "author": "/people/123"}'
     http://localhost:8080/api/books/

The de-serialization error happens when Jackson tries to resolve the /people/123 local URI which should resolve to a single, unique Person. If I remove my @RepositoryRestController, everything works fine. Any idea what's wrong with my REST controller definition?

回答1:

In the @RepositoryRestController, change the type of the @RequestBody argument from Book to Resource<Book>:

import org.springframework.hateoas.Resource;

    // ...

    @RequestMapping(method = RequestMethod.POST,value = "/books")
    public @ResponseBody PersistentEntityResource post(
        @RequestBody Resource<Book> bookResource,             // Resource<Book>
        PersistentEntityResourceAssembler assembler) {

        Book book = bookResource.getContent()
        // ...
    }

and in the Book entity definition modify the AllArgsConstructor annotation to be: @AllArgsConstructor(suppressConstructorProperties = true).

See Spring Data REST #687 for more information.

来源：https://stackoverflow.com/questions/40986738/spring-data-rest-no-string-argument-constructor-factory-method-to-deserialize

标签

java

Spring

java-8

spring-data-rest

Lombok