Hibernate映射 - 使用关联表连接两个表 - 但有一个转折点 [英] Hibernate Mapping - Joining two tables with an association table - But with a twist

问题描述

我有以下实体... 客户，卡片和地址 code>

客户：

  {
 private String cust_id; //主键
 ..... 
 
 @OneToOne 
地址地址; //我想加载客户的地址。 
 //可以将关联更改为@OneToMany，如果需要的话
} 
  

Card：

  {
 private String card_id; //主键
 private String cust_id; //外键Customer.cust_id 
 .... 
} 
  

地址：

  {
 private String card_id; // card.card_id的外键
 private String address1; 
 ..... 
} 
  

当我加载客户时，我想加载具有关联表卡片的地址。但棘手的部分是地址没有主键。它只有一个外键。

解决方案

您可以在@OneToOne之后使用注释@JoinTable指向卡片的表，你不需要卡片实体，但是如果卡片的表格不仅仅是关系表格，你可以将卡片作为@OneToOne映射到用户，并且有一个@Transient'getAddress（）'方法返回'this.card。 getAddress（）'，但在卡的实体上，您必须映射地址和卡之间的关系（@OneToOne（mappedBy ='card_id'）），并且在Address中，可以将card_id映射为@Id。

第一选择

顾客：

 （$ name =cust_id），
 inverseJoinColumns = @JoinColumn b $ b私人地址; 
  

第二种选择

顾客：

  @OneToOne（mappedBy =cust_id）
私人卡片卡; 
 
 ... 
 @Transient 
 public Address getAddress（）{
 return this.card == null？ null：this.card.getAddress（）; 
 
  

卡片：

  @OneToOne（mappedBy =card_id）
私有地址; 
  

地址：

  @Id 
 private String card_id; 
  

在第二种情况下，卡片有一个由两个fks（Customer和Address）组成的Embedded pk

卡片：

  @EmbeddedId $ b $ private CustomerAddressPK id; 
  

CustomerAddressPK

  @Embeddable 
 public class CustomerAddressPK（）{
 
 private String cust_id; 
私人字符串card_id; 
} 
  

I have the following entities... Customer, Card and Address

Customer:

 {
     private String cust_id; // Primary key
     .....

     @OneToOne
     Address address; // I want to load address of the customer. 
                      // Can change the association to @OneToMany, if needed
 }

Card:

 {
    private String card_id; // Primary Key
    private String cust_id; // Foreign Key to Customer.cust_id
    ....
 }

Address:

 {
    private String card_id; // Foreign key to card.card_id
    private String address1;
    .....
 }

When I load customers I want to load Addresses with association table Card. But the tricky part is Address does not have a primary key. It only has a Foreign key.

解决方案

You could use the annotation @JoinTable after the @OneToOne to point the card's table, so you won't need an entity for card, but if the card's table isn't just a relational table, you could map card in User as @OneToOne and have a @Transient 'getAddress()' method that returns 'this.card.getAddress()', but on card's entity you must map the relation between Address and Card(@OneToOne(mappedBy='card_id')), and in Address you could map card_id as @Id.

First Alternative

Customer:

@OneToOne
@JoinTable(name="card", joinColumns = @JoinColumn(name="cust_id"),
inverseJoinColumns = @JoinColumn(name="card_id"))
private Address address;

Second alternative

Customer:

@OneToOne(mappedBy="cust_id")
private Card card;

...
@Transient
public Address getAddress(){
 return this.card == null ? null : this.card.getAddress();
}

Card:

@OneToOne(mappedBy="card_id")
private Address address;

Address:

@Id
private String card_id;

In the Second case Card has a Embedded pk which is formed by two fks(Customer and Address)

Card:

@EmbeddedId
private CustomerAddressPK id;

CustomerAddressPK

@Embeddable
public class CustomerAddressPK(){

  private String cust_id;
  private String card_id;
}

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