i have a Class A and Class B,relation between these two are ONE(Class A)-To-MANY(Class B)

1)Class A is having

private Long identityId
private Long userId
private Set<Class B> setb = new HashSet<Class B>();

below is the content of classa.hbm.xml

<class name="ClassA" table="table_a">
<id name="identityId" column="identify_id"></id>
<property name="userId" column="user_id"></property>
<set name="setb" lazy="false" inverse="false">
<key column="user_id"></key>
<one-to-many class="ClassB"/>
</set>
</class>

2)Class B is having

private Long userId;
private Long respId;

below is the content of classb.hbm.xml

<class name="ClassB" table="table_b">
<id name="userId" column="user_id"></id>
<property name="respId" column="resp_id"></property>
</class>


I am trying to pull Class B data but its coming as NULL , Can some one let me know if there is any wrong with above mappings ?