Association references unmapped class exception with hibernate

hii to all

actually i am a new to hybernate and during make projects i get this exception and after spending 2 more days i am not able to find why this exception is comes please suggest me .
because i knew this error is coming during the getseeion to the database to load the mapping file .

please check where is my mapping is wrong ?

exception is
org.hibernate.MappingException: Association references unmapped class: com.tra.Generate.TraCurrentUsers
at org.hibernate.cfg.HbmBinder.bindCollectionSecondPass(HbmBinder.java:2380)
at org.hibernate.cfg.HbmBinder$CollectionSecondPass.secondPass(HbmBinder.java:2662)
at org.hibernate.cfg.CollectionSecondPass.doSecondPass(CollectionSecondPass.java:43)
at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1130)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1286)
at com.tra.manager.transaction.TransactionMngr.getSession(TransactionMngr.java:627)
at com.tra.manager.transaction.TransactionMngr.retrieveData(TransactionMngr.java:246)

i make my .hbm.xml and pojo by reverse enginnering i want to map usermaintenance table to the tracurrentusers and traroles

first .hbm file is

<?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="com.tra.Generate.UserMaintenance" table="USER_MAINTENANCE" schema="RAKESH">
        <comment>User Maintenance table</comment>
        <id name="userId" type="string">
            <column name="USER_ID" length="256" />
            <generator class="assigned" />
        </id>
        <property name="userPass" type="string">
            <column name="USER_PASS" length="256">
                <comment>Encrypted password</comment>
            </column>
        </property>
        <property name="userName" type="string">
            <column name="USER_NAME" length="256">
                <comment>User Name</comment>
            </column>
        </property>
        <property name="userBranch" type="string">
            <column name="USER_BRANCH" length="256">
                <comment>User Branch</comment>
            </column>
        </property>
        <property name="userEmail" type="string">
            <column name="USER_EMAIL" length="256">
                <comment>Email address of user</comment>
            </column>
        </property>
        <property name="userStartdate" type="date">
            <column name="USER_STARTDATE" length="7">
                <comment>Start date of user</comment>
            </column>
        </property>
        <property name="userExpirydate" type="date">
            <column name="USER_EXPIRYDATE" length="7">
                <comment>Expiry date of user</comment>
            </column>
        </property>
        <property name="lastLogin" type="date">
            <column name="LAST_LOGIN" length="7">
                <comment>Last successful login date</comment>
            </column>
        </property>
        <property name="creationDate" type="date">
            <column name="CREATION_DATE" length="7">
                <comment>User creation date</comment>
            </column>
        </property>
        <property name="createdBy" type="string">
            <column name="CREATED_BY" length="256">
                <comment>User id of the user who created this user</comment>
            </column>
        </property>
        <property name="lastModifiedDate" type="date">
            <column name="LAST_MODIFIED_DATE" length="7">
                <comment>Last modification date</comment>
            </column>
        </property>
        <property name="lastModifiedBy" type="string">
            <column name="LAST_MODIFIED_BY" length="256">
                <comment>User id of the user who modified this user</comment>
            </column>
        </property>
        <property name="disableFlag" type="java.lang.Character">
            <column name="DISABLE_FLAG" length="1">
                <comment>Set value to Y for disabling user</comment>
            </column>
        </property>
        <set name="traCurrentUserses" inverse="true">
            <key>
                <column name="USER_ID" length="256" not-null="true" unique="true">
                    <comment>Logged in user id</comment>
                </column>
            </key>
            <one-to-many class="com.tra.Generate.TraCurrentUsers" />
        </set>
        <set name="traRoleses" inverse="false" table="TRA_USER_ROLES">
            <key>
                <column name="USER_ID" length="256" not-null="true">
                    <comment>User id</comment>
                </column>
            </key>
            <many-to-many entity-name="com.tra.Generate.TraRoles">
                <column name="ROLE_ID" length="20" not-null="true">
                    <comment>Role id</comment>
                </column>
            </many-to-many>
        </set>
    </class>
</hibernate-mapping>

second one is

<?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="com.tra.Generate.TraCurrentUsers" table="TRA_CURRENT_USERS" schema="RAKESH">
        <comment>Table for storing logged in users ids and session ids</comment>
        <id name="userId" type="string">
            <column name="USER_ID" length="256" />
            <generator class="assigned" />
        </id>
        <many-to-one name="userMaintenance" class="com.tra.Generate.UserMaintenance" update="false" insert="false" fetch="select">
            <column name="USER_ID" length="256" not-null="true" unique="true">
                <comment>Logged in user id</comment>
            </column>
        </many-to-one>
        <many-to-one name="traProjects" class="com.tra.Generate.TraProjects" fetch="select">
            <column name="APP_ID" length="20">
                <comment>Application id of last access by this user</comment>
            </column>
        </many-to-one>
        <property name="sessionId" type="string">
            <column name="SESSION_ID" length="256">
                <comment>This users session id</comment>
            </column>
        </property>
        <property name="lastActivityTime" type="date">
            <column name="LAST_ACTIVITY_TIME" length="7">
                <comment>Last activity time</comment>
            </column>
        </property>
    </class>
</hibernate-mapping>

last third one is

<?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="com.tra.Generate.TraRoles" table="TRA_ROLES" schema="RAKESH">
        <comment>Role details</comment>
        <id name="roleId" type="string">
            <column name="ROLE_ID" length="20" />
            <generator class="assigned" />
        </id>
        <property name="roleDesc" type="string">
            <column name="ROLE_DESC" length="256">
                <comment>Role description</comment>
            </column>
        </property>
        <property name="creationDate" type="date">
            <column name="CREATION_DATE" length="7">
                <comment>Role creation date</comment>
            </column>
        </property>
        <property name="createdBy" type="string">
            <column name="CREATED_BY" length="256">
                <comment>Role created by user</comment>
            </column>
        </property>
        <property name="lastModificationDate" type="date">
            <column name="LAST_MODIFICATION_DATE" length="7">
                <comment>Last modification date</comment>
            </column>
        </property>
        <property name="lastModifiedBy" type="string">
            <column name="LAST_MODIFIED_BY" length="256">
                <comment>Last modified by user</comment>
            </column>
        </property>
        <set name="userMaintenances" inverse="true" table="TRA_USER_ROLES">
            <key>
                <column name="ROLE_ID" length="20" not-null="true">
                    <comment>Role id</comment>
                </column>
            </key>
            <many-to-many entity-name="com.tra.Generate.UserMaintenance">
                <column name="USER_ID" length="256" not-null="true">
                    <comment>User id</comment>
                </column>
            </many-to-many>
        </set>
        <set name="traRoleFunctionses" inverse="true">
            <key>
                <column name="ROLE_ID" length="20" not-null="true">
                    <comment>Role id</comment>
                </column>
            </key>
            <one-to-many class="com.tra.Generate.TraRoleFunctions" />
        </set>
    </class>
</hibernate-mapping>