gistfile1.txt

   <class name="Party" mutable="false">
        <join table="contract_party"
            inverse="true"
            optional="true">
            <key column="party"/>
            <many-to-one name="contract"
                column="contract"
                not-null="true"/>
        </join>
    </class>

	<class name="Contract" mutable="false">
		<set name="parties" table="contract_party" inverse="false"  mutable="true" cascade="all">
            <key column="contract"/>
            <many-to-many column="party" unique="true" class="Party"/>
        </set>
	</class>