How to modify beans defined in a spring container

Question

I have two xml files defining beans for the springframework (version 2.5.x):

containerBase.xml:
<beans>
    <bean id="codebase" class="com.example.CodeBase">
        <property name="sourceCodeLocations">
            <list>
                <value>src/handmade/productive</value>
            </list>
        </property>
    </bean>
</beans>

... and

containerSpecial.xml:
<beans>
    <import resource="containerBase.xml" />
</beans>

Now I want to adjust the property sourceCodeLocations of bean codebase within containerSpecial.xml. I need to add a second value src/generated/productive.

A simple approach is to override the definition of codebase in containerSpecial.xml and add both values, the one from containerBase.xml and the new one:

containerSpecial.xml:
<beans>
    <import resource="containerBase.xml" />

    <bean id="codebase" class="com.example.CodeBase">
        <property name="sourceCodeLocations">
            <list>
                <value>src/handmade/productive</value>
                <value>src/generated/productive</value>
            </list>
        </property>
    </bean>
</beans>

Is there a way to extend the list without redefining the bean?

EDIT 2009-10-06:

The purpose of this is to have a shared standard container containerBase that is used by a lot of different projects. Each project can override/extend some properties that are special for that project in its own containerSpecial. If the project doesn't override, it's using the defaults defined in containerBase.

Answer 1

Yes. A bean definition can have a "parent" attribute that references a parent bean definition. The new "child" definition inherits most of the properties of the parent and any of those properties can be overridden.

See Bean Definition Inheritance

Also you can use Collection Merging to merge the list property definition from the parent and child bean definitions. This way you can specify some list items in the parent bean definition and add more items to it in the child bean definition.

Answer 2

You could use a BeanFactoryPostProcessor to change the bean's metadata before the Spring container instantiates the CodeBase bean. For example:

public class CodebaseOverrider implements BeanFactoryPostProcessor {

    private List<String> sourceCodeLocations;

    public void postProcessBeanFactory(
            ConfigurableListableBeanFactory beanFactory) throws BeansException {        
        CodeBase codebase = (CodeBase)beanFactory.getBean("codebase");
        if (sourceCodeLocations != null)
        {
            codebase.setSourceCodeLocations(sourceCodeLocations);
        }
    }

    public void setSourceCodeLocations(List<String> sourceCodeLocations) {
        this.sourceCodeLocations = sourceCodeLocations;
    }

}

Then in contextSpecial.xml:

<beans>
    <import resource="context1.xml" />

    <bean class="com.example.CodebaseOverrider">
        <property name="sourceCodeLocations">
            <list>
                <value>src/handmade/productive</value>
                <value>src/generated/productive</value>
            </list>
        </property>
    </bean>
</beans>