java - 在 JPA 中以一对一关系共享主键的情况下如何访问对象？

Question

让我们看一下表结构:-

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`);

地址和客户通过 id 通过一对一关系进行映射。也就是说，customer.id 被分配给 address_id [我知道表的一列可能充当从其他表生成的主键]。

让我们看看实体:-

@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
        );
    }

}

Controller 类:-

@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;
    }
}

问题:-

我关注JPA Hibernate One-to-One relationship

1. /customer-with-address/5 属于递归。如何摆脱递归？
2. /save-customer-with-address 将数据保存到数据库后，将客户对象的地址返回为 null。这是因为地址未设置为客户对象。当我尝试将地址设置为客户对象时，它也陷入递归。那么，如何设置/获取地址对象到客户对象？
3. 我像以前一样从任何实体完成一对一映射。但这里的映射是从两侧完成的。 我可以从任何方面做吗？

注意:-如果我在 address 表中添加一个额外的列 customer_id ，所有问题都可以轻松解决。但我不想添加 customer_id。我提前感谢您的宝贵意见。

Answer 1

1. 检查您是否递归调用方法或对其进行调试

2. 客户中有设置者

   设置地址(a){ a.setCustomer(this); 这个地址=a; }

3. https://en.wikibooks.org/wiki/Java_Persistence/OneToOne#Example_of_an_inverse_OneToOne_relationship_annotations