spring: set property of one bean by reading the property of another bean?

Question

Is it possible to set the property of one bean by reading the property of another bean? For instance, suppose I had:

class A {
   void setList(List list);
}

class B {
   List getList();
}

I would like Spring to instantiate both classes, and call A's setList method, passing in the result of calling B's getList method. The Spring configuration might look something like:

<bean id="b" class="B"/>
<bean id"a" class="A">
    <property name="list" ref="b" ref-property="list"/>
</bean>

Alas, this made-up XML does not work.

Why not just inject B into A? Because I do not want to introduce the extra dependency. A is only dependent List, not on B.

Answer 1

There are a couple of ways. Here is one:

<bean id="b" class="B"/>
<bean id="a" class="A">
    <property name="list">
        <bean class="org.springframework.beans.factory.config.PropertyPathFactoryBean">
            <property name="targetObject" ref="b"/>
            <property name="propertyPath" value="list"/>
        </bean>
    </property>
</bean>

Also see the <util:property-path/> element

Answer 2

in addition to @Kevin's answer if you are using spring 3.0 it is possible to do this with the new spring expression language

<bean id="a" class="A">
    <property name="list"
        value="#{b.list}"/>
</bean>

spring 3.0 documentation