Spring: Nested application contexts

Question

I have a hierarchy of application contexts. The bean that is defined in the parent context depends on a bean that is defined in the child. Here's how it looks like:

  public class X {

     public static class A {
        public B b;
        public void setB(B b) { this.b = b; }
     }

     public static class B { }

     public static void main(String[] args) {
        ClassPathXmlApplicationContext parent = new ClassPathXmlApplicationContext(
           "/a.xml");
        go1(parent);
     }

     public static void go1(ClassPathXmlApplicationContext parent) {
        GenericApplicationContext child = new GenericApplicationContext(parent);

        child.getBeanFactory().registerSingleton("b", new B());

        A a = (A) child.getBean("a");
        Assert.assertNotNull(a.b);
     }
  }

The xml file defining the "a" bean looks like this:

  <?xml version="1.0" encoding="UTF-8"?>

  <beans xmlns="http://www.springframework.org/schema/beans"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://www.springframework.org/schema/beans
         http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">

    <bean id="a" class="X$A" autowire="byName" lazy-init="true"/>


  </beans>

The problem is that B is not injected into A. Injection will occur only if I register the "b" singleton with the parent - which is not an option in my program.

Any ideas?

Answer 1

You can't do that. Parent contexts cannot refer to bean definitions in the child contexts. It only works the other way around.