JPA 1个关系表，2个独立类使用一个带有@OneTomany的公共类

Question

基本上，我想影响公司和个人的地址。地址是独立的实体。

public class Address {
}

public class AddressContext {
    private Address address;
    private String name;
}

public class Individual {
   @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
   private Set<AddressContext> addresseContexts;
}

public class Company {
   @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
   private Set<AddressContext> addresseContexts;
}

CREATE TABLE `address_Context` (
   `ID` bigint(20) NOT NULL AUTO_INCREMENT,
   'address_id bigint(20) NOT NULL, 
   'RELATED_ITEM_ID bigint(20) NOT NULL,
   'RELATED_ITEM_TYPE varchar(50) NOT NULL,
   'NAME' varchar(5) 
);

1, 1, 1, Individual, 'John's House';
2, 2, 1, Company, 'Depoy';

companies_address_contexts
individuals_address_contexts

提前致谢

Answer 1

您不想将特定地址限制为实体类型（个人/公司）。想想（边缘）情况下，一个自营职业者使用他们的家庭地址作为他们的公司地址。或者将多租户单元转换为办公大楼的情况。您得到了要点-地址应该是完全独立的实体，系统中的其他实体然后通过关联表引用这些实体。

在您的例子中，关联表已经生成，您只需要一些小的重构就可以在代码中使用它们（一种形式）。类似于这样：

@Entity
public class Address {
    // address fields etc
}

@Entity
public class Individual {
   @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
   @JoinTable(name = "individual_addresses", 
       joinColumns = { @JoinColumn(name = "individual_id", unique = true) }, 
       inverseJoinColumns = { @JoinColumn(name = "address_id") })
   private Set<Address> addresses;
}

@Entity
public class Company {
   @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
   @JoinTable(name = "company_addresses", 
       joinColumns = { @JoinColumn(name = "company_id", unique = true) }, 
       inverseJoinColumns = { @JoinColumn(name = "address_id") })
   private Set<Address> addresses;
}