public void testInstantiateCompositeDependingOnComponentArrayRequiresPreInstantiationAndCaching() {
MutablePicoContainer pc = new DefaultPicoContainer();
pc.registerComponentImplementation(LeafComponent.class);
pc.registerComponentInstance("apple");
Collection comps = pc.getComponentInstancesOfType(Component.class);
assertEquals(1, comps.size());
pc.registerComponentInstance("x", comps.toArray());

Object[] arr = (Object[]) pc.getComponentInstance("x");

assertNotNull(arr);
assertEquals(1, arr.length);

pc.registerComponentImplementation(CompositeComponent.class,
CompositeComponent.class,
new Parameter[] {new ComponentParameter("x")});

Component cc = (Component) pc.getComponentInstance(CompositeComponent.class);

assertNotNull(cc);
assertEquals("apple", cc.toString());
}

Even so, it would still be nice for the following to just work with minimal extra config. I guess this is related to Thomas' comments on the list about the greedy nature of the GCCA – see http://article.gmane.org/gmane.comp.java.picocontainer.devel/3491. If I have any ideas for improvement I'll speak up on the list or submit another patch.

public static interface Component {}

public static class CompositeComponent implements Component {
Object[] children;

public CompositeComponent(Object[] children) { this.children = children; }
}

public static class LeafComponent implements Component {
public LeafComponent() {
}
}

pc.registerComponentInstance(LeafComponent.class);
pc.registerComponentInstance(CompositeComponent.class);