This is an way to pass the id of another bean in the container in <constructor-arg/> or <property/> element)

Java Code:
<bean id="ServerBean" class="..."/>
<bean id="ClientBean" class="...">
<property name="IpName">
<idref bean="ServerBean" />
</property>
</bean>
The above bean definition is exactly equivalent (at runtime) to the following:

Java Code:
<bean id=" ServerBean " class="..."/>
<bean id="clientBean " class="...">
<property name=" IpName
<value> ServerBean </value>
</property>
</bean>