Spring's overriding bean

Question

Can we have duplicate names for the same bean id that is mentioned in the XML? If not, then how do we override the bean in Spring?

Answer 1

Any given Spring context can only have one bean for any given id or name. In the case of the XML id attribute, this is enforced by the schema validation. In the case of the name attribute, this is enforced by Spring's logic.

However, if a context is constructed from two different XML descriptor files, and an id is used by both files, then one will "override" the other. The exact behaviour depends on the ordering of the files when they get loaded by the context.

So while it's possible, it's not recommended. It's error-prone and fragile, and you'll get no help from Spring if you change the ID of one but not the other.

Answer 2

I will add that if your need is just to override a property used by your bean, the id approach works too like skaffman explained :

In your first called XML configuration file :

   <bean id="myBeanId" class="com.blabla">        <property name="myList" ref="myList"/>    </bean>     <util:list id="myList">        <value>3</value>        <value>4</value>    </util:list> 

In your second called XML configuration file :

   <util:list id="myList">        <value>6</value>    </util:list> 

Then your bean "myBeanId" will be instantiated with a "myList" property of one element which is 6.