通常為了實(shí)現(xiàn)entity class的雙向association,每添加一組實(shí)例在java中需要兩行代碼:

persion.getAddresses().add(address);
address.getPersons().add(person);

但對Hibernate而已，上面的代碼會被轉(zhuǎn)化為兩條insert語句，

為了避免這樣的情況出現(xiàn)需要定義inverse屬性，告訴Hibernate persion和address之間的關(guān)系：

// !file: Person.class
public class Person {
    // ...
    @ManyToMany(
              targetEntity= Address.class,
              cascade = CascadeType.ALL,
      )
    @JoinTable(
              name="persion_address",
              joinColumns= {@JoinColumn(name="person_id")},
              inverseJoinColumns= {@JoinColumn(name="address_id")}
      )
      private Set<Address> adressses = new HashSet<Address> (0);
    // ...
}

// !file: Address.class
public class Address {
    // ...
    @ManyToMany(
            targetEntity= Persion.class,
            cascade = CascadeType.ALL, 
            mappedBy = "addresses"
    )
    private Set<Person> persons = new HashSet<Person>();
    // ...
}

上面的兩個(gè)annotation告訴Hibernate，Person是主，對Address中persons屬性的修改將不會產(chǎn)生SQL語句。

Hibernate里，如果是Many-to-many的關(guān)系，可以任意設(shè)置主class。

通常，還可以將添加刪除關(guān)系的代碼包裝起來:

// !file: Person.class
public class Person {
    // ...
    public void addAddress(Address address) {
        this.getAddresses().add(address);
        address.getPersons().add(this);
    }
    public void removeAddress(Address address) {
        this.getAddresses().remove(address);
        address.getPersons().remove(this);
    }
    //...
}