Guice assisted injection deeper down the dependency hierarchy

by

Cheating way: Stick input in a static variable or singleton ThreadLocal. Set it before your pipeline starts and clear it after it ends. Bind everything else through DI.

Fancy way: In A, refer to a @PipelineInput String inputString but don’t bind it in your main injector. Otherwise, bind dependencies as you normally would, including referring to @PipelineInput in other pipeline-related classes. When you do need a D, get it from your implementation of a DFactory, which I’m calling PipelineRunner.

public class PipelineRunner {
  @Inject Injector injector; // rarely a good idea, but necessary here

  public D createD(final String inputForA) {
    Module module = new AbstractModule() {
      @Override public void configure() {
        bindConstant(inputForA).annotatedWith(PipelineInput.class);
      }
    };
    return injector.createChildInjector(new PipelineModule(), module)
        .getInstance(D.class);
  }
}

Naturally, binding attempts for A, B, C, and D will fail outside of PipelineRunner for lack of a @PipelineInput String–you’ll get a CreationException when you create the injector with those unsatisfied dependencies, as you discovered–but those pipeline-based dependencies should be easy to separate into a Module that you install into the child injector.

If this feels too hacky, remember that PrivateModules are also “implemented using parent injectors“, and that the whole point of dependency injection is to make a dependency like inputForA available to the whole object graph in a decoupled way.

More Related Contents:

  1. Overriding Binding in Guice
  2. Inject Generic Implementation using Guice
  3. Why is HttpServletRequest inputstream empty?
  4. How to implement the “robot legs” use case with Google Guice?
  5. How to instantiate Spring managed beans at runtime?
  6. How to add two object together
  7. Java code to find balance no of days in a financial year [closed]
  8. Under what conditions is a JSESSIONID created?
  9. Setting user agent of a java URLConnection
  10. How do Mockito matchers work?
  11. How to delete stuff printed to console by System.out.println()?
  12. How to add native library to “java.library.path” with Eclipse launch (instead of overriding it)
  13. Unable to compile class for JSP: The type java.util.Map$Entry cannot be resolved. It is indirectly referenced from required .class files
  14. Is it possible to create an instance of inner class using Java Reflection?
  15. Android: how to parse URL String with spaces to URI object?
  16. Can I add new methods to the String class in Java?
  17. Java 8 Stream with batch processing
  18. clear screen option in java [duplicate]
  19. Math.abs returns wrong value for Integer.Min_VALUE
  20. Create the perfect JPA entity [closed]
  21. How do I resize images inside an application when the application window is resized?
  22. Netty doesn’t write
  23. How to validate against schema in JAXB 2.0 without marshalling?
  24. SpringData : is it possible to have subqueries in the Query annotation?
  25. Checking file existence on FTP server
  26. Printing out a 2D array in matrix format
  27. Google Guava “zip” two lists
  28. Testing console based applications/programs – Java
  29. org.dbunit.dataset.NoSuchTableException: Did not find table ‘xxx’ in schema ‘null’
  30. JavaFX Spell checker using RichTextFX how to create right click suggestions

Leave a Comment