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讓我們看一下表結構： -如何在共享主鍵的情況下訪問對象作爲JPA中的一對一關係？
CREATE TABLE `customer` (
`id` bigint(20) UNSIGNED AUTO_INCREMENT NOT NULL,
`first_name` varchar(150) COLLATE utf8_unicode_ci NOT NULL,
`last_name` varchar(150) COLLATE utf8_unicode_ci NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
ALTER TABLE `customer` ADD PRIMARY KEY (`id`);
-------------------------------------------------------------
CREATE TABLE `address` (
`id` bigint(20) UNSIGNED NOT NULL,
`street` varchar(512) COLLATE utf8_unicode_ci NOT NULL,
`city` varchar(512) COLLATE utf8_unicode_ci NOT NULL,
`country` varchar(512) COLLATE utf8_unicode_ci NOT NULL,
`postal_code` varchar(512) COLLATE utf8_unicode_ci NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
ALTER TABLE `address` ADD PRIMARY KEY (`id`);
地址&客戶通過id通過一個一對一的關係映射。那就是customer.id被分配給address_id [I know that a column of a table may role as a primary-key which is generated from some other table]。
讓我們看看實體： -
@Entity
public class Customer {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String firstName;
private String lastName;
@OneToOne
@PrimaryKeyJoinColumn
private Address address;
// getters & setters
@Override
public String toString() {
return String.format(
"Customer[id=%d, firstName='%s', lastName='%s', address='%s']",
id, firstName, lastName, address
);
}
}
//////////////////////////////////////////////////////////////////////////
@Entity
public class Address {
@Id @GeneratedValue(generator = "customForeignGenerator")
@org.hibernate.annotations.GenericGenerator(
name = "customForeignGenerator",
strategy = "foreign",
parameters = @Parameter(name = "property", value = "customer")
)
private Long id;
private String street;
private String city;
private String country;
private String postalCode;
@OneToOne(mappedBy="address")
@PrimaryKeyJoinColumn
public Customer customer;
// getters & setters
@Override
public String toString() {
return String.format(
"Address[id='%d', street='%s', city='%s', country='%s', postalCode='%s']",
id, street, city, country, postalCode
);
}
}
控制器類： -
@RestController
@RequestMapping("/api/customers")
public class CustomerRestController {
// CustomerRepository extends CrudRepository<Customer, Long>
@Autowired
private CustomerRepository customerRepository;
// AddressRepository extends CrudRepository<Address, Long>
@Autowired
private AddressRepository addressRepository;
@RequestMapping("/customer-with-address/{customerId}")
public Customer getCustomerWithAddress(@PathVariable("customerId") Long customerId) {
return customerRepository.findOne(customerId);
}
@RequestMapping("/save-customer-with-address")
public Customer getCustomer() {
Customer customer = new Customer();
customer.setFirstName("ABC");
customer.setLastName("XYZ");
Customer customer1 = customerRepository.save(customer);
Address address = new Address();
address.setStreet("street " + customer1.getId());
address.setCity("city " + customer1.getId());
address.setCountry("country " + customer1.getId());
address.setPostalCode("postal_code " + customer1.getId());
address.setCustomer(customer1);
addressRepository.save(address);
return customer;
}
}
問題： -
我跟着JPA Hibernate One-to-One relationship
/customer-with-address/5屬於遞歸。我如何從遞歸轉義？/save-customer-with-address將數據保存到數據庫之後，將客戶對象的地址返回爲空。這是因爲地址未設置爲客戶對象。當我試圖爲客戶對象設置地址時，它也落入遞歸中。那麼，我該如何設置/獲取客戶對象的地址對象？- 我
one-to-one從任何實體做的映射，就像我以前做的那樣。但是這裏的映射是從兩側完成的。 我可以從任何一方做什麼？
N.B： -所有的問題都可以很容易，如果我把一個額外的列customer_id到地址表來解決。但我不想添加customer_id。我提前感謝您的寶貴意見。