我是Spring的新手，我无法弄清楚如何联接多个表以返回一些结果。我试图实现一个小型的Library应用程序，如下所示。
我的实体类-书籍，客户，预订
Book.java-库中可用的书
@Entity
@Table(name = "books")
public class Book {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id", columnDefinition = "int")
private int id;
@NotNull(message = "Book name cannot be null")
@Column(name = "book_name", columnDefinition = "VARCHAR(255)")
private String bookName;
@Column(name = "author", columnDefinition = "VARCHAR(255)")
private String author;
// getters and setters
public Book() {}
public Book(String bookName, String author) {
this.bookName = bookName;
this.author = author;
}
}
Customer.java-在库中注册的客户
@Entity
@Table(name = "customer", uniqueConstraints = {@UniqueConstraint(columnNames = {"phone"})})
public class Customer {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id", columnDefinition = "int")
private int id;
@NotNull(message = "Customer name cannot be null")
@Column(name = "name", columnDefinition = "VARCHAR(255)")
private String name;
@Column(name = "phone", columnDefinition = "VARCHAR(15)")
private String phone;
@Column(name = "registered", columnDefinition = "DATETIME")
private String registered;
// getters and setters
public Customer() {}
public Customer(String name, String phone, String registered) {
this.name = name;
this.phone = phone;
this.registered = registered;
}
}
Booking.java-客户进行的所有预订
@Entity
@Table(name = "bookings")
public class Booking {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id", columnDefinition = "int")
private int id;
@NotNull(message = "Book id cannot be null")
@Column(name = "book_id", columnDefinition = "int")
private int bookId;
@NotNull(message = "Customer id cannot be null")
@Column(name = "customer_id", columnDefinition = "int")
private int customerId;
@Column(name = "issue_date", columnDefinition = "DATETIME")
private String issueDate;
@Column(name = "return_date", columnDefinition = "DATETIME")
private String returnDate;
// getters and setters
public Booking() {}
public Booking(int bookId, int customerId, String issueDate) {
this.bookId = bookId;
this.customerId = customerId;
this.issueDate = issueDate;
}
}
现在，各个实体的表模式如下:
books: +-----------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------+--------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | book_name | varchar(255) | NO | | NULL | | | author | varchar(255) | YES | | NULL | | +-----------+--------------+------+-----+---------+----------------+ id - primary key customer: +------------+--------------+------+-----+-------------------+-------------------+ | Field | Type | Null | Key | Default | Extra | +------------+--------------+------+-----+-------------------+-------------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | name | varchar(255) | NO | | NULL | | | registered | datetime | YES | | CURRENT_TIMESTAMP | DEFAULT_GENERATED | | phone | varchar(15) | YES | UNI | NULL | | +------------+--------------+------+-----+-------------------+-------------------+ id - primary key bookings: +-------------+----------+------+-----+-------------------+-------------------+ | Field | Type | Null | Key | Default | Extra | +-------------+----------+------+-----+-------------------+-------------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | book_id | int(11) | NO | MUL | NULL | | | customer_id | int(11) | NO | MUL | NULL | | | issue_date | datetime | YES | | CURRENT_TIMESTAMP | DEFAULT_GENERATED | | return_date | datetime | YES | | NULL | | +-------------+----------+------+-----+-------------------+-------------------+ id - primary key book_id - foreign key references books.id customer_id - foreign key references customer.id
Now What I want to do is given some booking critieria like customer phone or author name etc., I want to return all the bookings related to that order. I'll show a sample Booking api to explain.
Booking Controller:
@RestController
@RequestMapping("/bookings")
public class BookingController {
@Autowired
BookingService bookingService;
// some booking apis which return Booking objects
@GetMapping
public List<Booking> getAllBookingsBy(@RequestParam("phone") String phone,
@RequestParam("authors") List<String> authors) {
return bookingService.getAllBy(phone, authors);
}
@PostMapping
public Booking addBooking(@RequestBody Booking booking) {
bookingService.saveBooking(booking);
return booking;
}
}
预订服务等级:
@Service
public class BookingService {
@Autowired
private BookingRepository bookingRepository;
// some booking service methods
// get all bookings booked by a customer with matching phone number and books written by a given list of authors
public List<Booking> getAllBy(String phone, List<String> authors) {
return bookingRepository.queryBy(phone, authors);
}
public void saveBooking(Booking booking) {
bookingRepository.save(booking);
}
}
预订存储库类:
@Repository
public interface BookingRepository extends JpaRepository<Booking, Integer> {
// some booking repository methods
@Query(value = "SELECT * FROM bookings bs WHERE " +
"EXISTS (SELECT 1 FROM customer c WHERE bs.customer_id = c.id AND c.phone = :phone) " +
"AND EXISTS (SELECT 1 FROM books b WHERE b.id = bs.book_id AND b.author IN :authors)",
nativeQuery = true)
List<Booking> queryBy(@Param("phone") String phone,
@Param("authors") List<String> authors);
}
现在点击显示的预订 Controller ，将返回一个看起来像这样的预订对象:
[
{
"id": 3,
"book_id": 5,
"customer_id": 2,
"issue_date": "2019-02-04 01:45:21",
"return_date": null
}
]
但是我不想这样，我想和他们一起返回预订的客户名称和书名。因此，我希望 Controller 返回的预订对象看起来像这样:
[
{
"id": 3,
"book_id": 5,
"customer_id": 2,
"issue_date": "2019-02-04 01:45:21",
"return_date": null,
"customer_name": "Cust 2",
"book_name": "Book_2_2",
}
]
有人可以帮忙吗？我被困住了，因为我无法从这里继续。
＃
编辑:
我在预订类中添加了这些单向的onetoone关联:
@OneToOne
@JoinColumn(name = "book_id", insertable = false, updatable = false)
private Book book;
@OneToOne
@JoinColumn(name = "customer_id", insertable = false, updatable = false)
private Customer customer;
但是现在，当我击中 Controller 时，我将整个Book和Customer对象都放入了Booking对象中。那么，如何在预订对象中返回书名和客户名呢？这是我的预订对象返回的样子:
[
{
"id": 3,
"book_id": 5,
"book": {
"id": 5,
"book_name": "Book_2_2",
"author": "author_2"
},
"customer_id": 2,
"customer": {
"id": 2,
"name": "Cust 2",
"phone": "98765431",
"registered": "2019-02-04 01:13:16"
},
"issue_date": "2019-02-04 01:45:21",
"return_date": null
}
]
而且现在我的预订 Controller 中的save()api无法正常工作，因为当我向其发送类型为Booking的对象时，bookId和customerId都以某种方式变为0，这在我添加这些更改之前没有发生。
最佳答案
你做错了。您正在返回预订，并且希望它神奇地反序列化为包含诸如书名之类的联接信息的实体。但是，在对存储库的选择查询中，您已经选择了预订。实现过程中的方式预订不包含有关预订的信息。
首先，您需要分离将反序列化为JSON的内容和将用作 Spring 数据的持久层的内容。
@OneToOne/@OneToMany关系。 实际上，如果您映射为OneToOne，则默认初始化为EAGER，因此查询变得有点不必要。
如果我们假设您在持久层中拥有正确的映射，那么您的查询将如下所示:
@Query(value = "SELECT * FROM bookings bs WHERE " +
"bs.customer.phone = :phone) " +
"AND bs.book.author IN :authors)")
这是您来自Hibernate的映射文档>
http://docs.jboss.org/hibernate/orm/5.4/userguide/html_single/Hibernate_User_Guide.html#associations
关于java - 如何在Spring JPA存储库中联接多个表的结果，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/54507552/