通常为了实现entity class的双向association,每添加一组实例在java中需要两行代码:

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

但对Hibernate而已，上面的代码会被转化为两条insert语句，

为了避免这样的情况出现需要定义inverse属性，告诉Hibernate persion和address之间的关系：

// !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>();
    // ...
}

上面的两个annotation告诉Hibernate，Person是主，对Address中persons属性的修改将不会产生SQL语句。

Hibernate里，如果是Many-to-many的关系，可以任意设置主class。

通常，还可以将添加删除关系的代码包装起来:

// !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);
    }
    //...
}