命名实体的休眠自动映射

Question

在我当前的 Spring Boot REST 示例项目中，我有两个实体（Book 和 BookSummary）均由 PagingAndSortingRepository 提供。 Book 实体如下所示：

@Entity(name = "Book")
public class Book
{
    @Id
    @GeneratedValue(generator = "UUID")
    @GenericGenerator(name = "UUID", strategy = "org.hibernate.id.UUIDGenerator")
    private UUID uuid;

    private String title;

    private String author;

    private String publisher;

    @Transient
    private String type = "Book";

    ...[Getter & Setter]...
}

BookSummary 实体如下所示：

@Entity(name = "Book")
public class BookSummary
{
    @Id
    @GeneratedValue(generator = "UUID")
    @GenericGenerator(name = "UUID", strategy = "org.hibernate.id.UUIDGenerator")
    private UUID uuid;

    private String title;

    private String author;

    @Transient
    private String type = "BookSummary";

    ...[Getter & Setter]...
}

PagingAndSortingRepository 实体如下所示：

@Repository
public interface BookRepository extends PagingAndSortingRepository<Book, UUID>
{
    Page<Book> findAll(Pageable pageable);
}

BooksRestController 实体如下所示：

@RestController
@RequestMapping("/books")
public class BooksRestController
{
    @GetMapping("/{uuid}")
    public Book read(@PathVariable UUID uuid)
    {
        return bookRepository.findOne(uuid);
    }

    @GetMapping
    public Page<Book> read(Pageable pageable)
    {
        return bookRepository.findAll(pageable);
    }

    @Autowired
    private BookRepository bookRepository;
}

关于PagingAndSortingRepository 和BooksController 实现，我假设REST 服务将通过/books 路由提供Book 实体的集合。但是该路由提供了BookSummary 实体的集合：

{
    content: [
        {
            uuid: "41fb943e-fad4-11e7-8c3f-9a214cf093ae",
            title: "Some Title",
            author: "Some Guy",
            type: "BookSummary"
        },
        ...
    ]
}

books/41fb943e-fad4-11e7-8c3f-9a214cf093ae 路由却提供了Book 摘要（如预期的那样）：

{
    uuid: "41fb943e-fad4-11e7-8c3f-9a214cf093ae",
    title: "Some Title",
    author: "Some Guy",
    publisher: "stackoverflow.com"
    type: "Book"
}

有人可以帮助我理解 Hibernate 的以下行为吗？

Answer 1

我猜 Hibernate 会感到困惑，因为您通过使用以下注释来命名两个具有相同实体名称的实体类：

@Entity(name = "Book")

在这种情况下，您应该简单地使用 @Entity 并让 Hibernate 使用实体类的非限定名称。

为每个实体创建一个存储库也是一种好习惯：一个用于Book 实体，第二个用于BookSummary 实体。我不得不说，我从未见过用于两个不同实体的 Spring Data 存储库。无论如何，您的控制器逻辑可能如下：

@RestController
@RequestMapping("/books")
public class BooksRestController
{
    private final BookRepository bookRepository;
    private final BookSummaryRepository bookSummaryRepository;

    @Autowired
    public BooksRestController(BookRepository bookRepository, BookSummaryRepository bookSummaryRepository)
    {
        this.bookRepository = bookRepository;
        this.bookSummaryRepository = bookSummaryRepository;
    }

    @GetMapping("/{uuid}")
    public BookSummary read(@PathVariable UUID uuid)
    {
        return bookSummaryRepository.findOne(uuid);
    }

    @GetMapping
    public Page<Book> read(Pageable pageable)
    {
        return bookRepository.findAll(pageable);
    }
}