RE: [picocontainer-dev] Tiering support 4 Pico

Well, this is related to a topic we had on the list before: How to publish components of a contain er explicitly i.e. only published components can be looked up by child containers or directly, while unpublished components can be used for dependency resolution of components within the same container. Maybe we can come up with something that covers both cases.

Use case for explicit publishing was always the addition of "modules" with own Pico hierarchies that should not expose internal deps to clients.

Paul Hammant wrote:
> I've shoved in a new class org.picocontainer.containers.TieringGuard
> (subject to rename). 
> 
> And there's a testcase at the bottom of DPCTC  (
> http://svn.codehaus.org/picocontainer/java/2.x/trunk/pico/cont
> ainer/src/test/org/picocontainer/DefaultPicoContainerTestCase.java   )
> 
>      public static class Couch {
>      }
> 
>      public static class TiredPerson {
>          private Couch couchToSitOn;
>          public TiredPerson(Couch couchToSitOn) {
>              this.couchToSitOn = couchToSitOn;
>          }
>      }
> 
>      @Test public void
> testThatParentTraversalForComponentsCanBeBlocked() {
>          DefaultPicoContainer grandparent = new
> DefaultPicoContainer();
>          DefaultPicoContainer parent = (DefaultPicoContainer)
> grandparent.makeChildContainer();
>          parent.setTiering(true);
>          DefaultPicoContainer child = (DefaultPicoContainer)
>          parent.makeChildContainer(); child.setTiering(true);
>          grandparent.addComponent(Couch.class);
>          child.addComponent(TiredPerson.class);
> 
>          TiredPerson tp = null;
>          try {
>              tp = child.getComponent(TiredPerson.class);
>              fail("should have barfed");
>          } catch
> (AbstractInjector.UnsatisfiableDependenciesException
> e) {
>              System.out.println("");
>              // expected
>          }
> 
>      }
> The idea is that in a tiered application, you should only depend on
> the classes from the immediate tier below you.
> Thus DPC now has a setTiering(boolean) method (subject to rename).
> TieringGuard uses a static ThreadLocal to indicate to parents that
> we're traversing towards the root of the container tree to fill deps.
> Comments appreciated. - Paul
> 
> 
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