Hibernate many-to-many data retrieval

问题

I have two objects User and Contact, with many to many relation, and I am using an intermediate table for this relation USER_CONTACT

Saving the data in this association is fine, but the retrieval is an issue.

I need to retrieve the data based on the User, but what I am getting is all the Contacts, for all the Users.

It will be good if you can let me know what wrong I am doing.

public class User {
private Integer userID;
private String  userLoginEmail;
private String  password;
private Set<Contact> contactSet = new HashSet<Contact>();
.
.
}

public class Contact implements Serializable {
private Integer contactID;
private String  givenName;
private String  familyName;
private Set<User>   userSet = new HashSet<User>();
.
.
}

User.hbm.xml:

<class name="User" table="USERACCOUNT">
    <id column="USER_ID" length="500" name="userID">
        <generator class="increment" />
    </id>
    <property column="USER_LOGIN_EMAIL" generated="never" lazy="false" length="100" name="userLoginEmail" />
    <property column="USER_FIRSTNAME" generated="never" lazy="false" length="100" name="userFirstName" />
    <property column="USER_LASTNAME" generated="never" lazy="false" length="100" name="userLastName" />
    <set name="contactSet" table="USER_CONTACT" inverse="false" lazy="false" fetch="select" cascade="all">
        <key column="USER_ID"/>
        <many-to-many column="CONTACT_ID" class="com.smallworks.model.Contact"/>
    </set>
</class>

Contact.hbm.xml

 <class name="Contact" table="CONTACT">
  <id column="CONTACT_ID" length="500" name="contactID">
   <generator class="increment"/>
  </id>
  <property column="GIVEN_NAME" generated="never" lazy="false"  length="100" name="givenName"/>
  <property column="FAMILY_NAME" generated="never" lazy="false" length="100" name="familyName"/>

  <!-- many to many mapping with the User via User_Contact table -->
  <set inverse="true" lazy="false" name="userSet" sort="unsorted" table="USER_CONTACT">
    <key column="USER_ID"/>
    <many-to-many class="com.smallworks.model.Contact" column="CONTACT_ID" unique="false"/>
  </set>
</class>

and this is how I am trying to retrieve the data, which I think is not correct.

List contactList = session.createQuery("from Contact").list();

It will be good if I can know how to go about getting the Contacts based on the User.

回答1:

// First, retrieve the user you want.
User user = (User) session.get(User.class, user_id_you_want);
// Second, get the contacts of that given user and add them to a list (optional)
List contacts = new ArrayList();
contacts.addAll(user.getContactSet());
return contacts;

来源：https://stackoverflow.com/questions/15868868/hibernate-many-to-many-data-retrieval