I know this has to be documented somewhere but I can not find it.

I have a many to many (users to groups) and want to find all the users by what group they are in.

Hibernate version: 3.0.5

Mapping documents:
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="UserBean" table="USER">
<id name="id" type="long">
<column name="USER_ID" not-null="true"/>
<generator class="sequence">
<param name="sequence">USER_SEQ</param>
</generator>
</id>
...
<set name="groups" lazy="true" table="USER_GROUP">
<key column="USER_ID"/>
<many-to-many column="GROUP_ID" class="GroupBean"/>
</set>
</class>
</hibernate-mapping>

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="GroupBean" table="GROUP">
<id name="id" type="long">
<column name="GROUP_ID" not-null="true"/>
<generator class="sequence">
<param name="sequence">GROUP_SEQ</param>
</generator>
</id>
...
</class>
</hibernate-mapping>

db scripts

CREATE TABLE USER
(
USER_ID NUMBER(12) NOT NULL,
...
CONSTRAINT USER_PK PRIMARY KEY (USER_ID),
)

CREATE TABLE GROUP
(
GROUP_ID NUMBER(12) NOT NULL,
...
CONSTRAINT GROUP_PK PRIMARY KEY (GROUP_ID),
)

CREATE TABLE USER_GROUP
(
USER_ID NUMBER(12) NOT NULL,
GROUP_ID NUMBER(12) NOT NULL,
CONSTRAINT USER_GROUP_PK PRIMARY KEY (USER_ID, GROUP_ID),
CONSTRAINT USER_FK FOREIGN KEY (USER_ID)
REFERENCES USER(USER_ID),
CONSTRAINT GROUP_FK FOREIGN KEY (GROUP_ID)
REFERENCES GROUP(GROUP_ID)
)

POJOs

public class UserBean {

private Set groups;
private long id;
// getter and setter exist
}

public class GroupBean {
private String id;
// getter and setter exist
}

Note my groupbean does not have a set of users because I am worried about circular fetches (I get a user, that uses has a group that group has users those users have groups) if I need the group to have a set of users and have the many-to-many reflected on both sides then how do I avoid the circular fetching?

thanks

This is really pretty simple using the Criteria interface:

(Assume groupId contains the id of the group you are searching for.)



BTW: You don't need to worry about circular fetching. Hibernate takes care of this for you.