使用Guice,如何注入超类的构造函数参数？

Question

可能重复:
与父母的Guice

class Book{string title;}
class ChildrensBook extends Book{}
class ScienceBook extends Book{} 

我想将书名注入子类中,例如,childrensBook应该为"爱丽丝梦游仙境"分配标题,并且ScienceBook应该获得"物种起源".我如何用Guice实现这一目标？

(注意我不想覆盖title子类中的字段)

Answer 1

以前在这里问过并回答:

埋藏在Guice最佳实践的最小可变性部分中,您将找到以下指南:

子类必须调用super()所有依赖项.这使构造函数注入变得麻烦,尤其是当注入的基类发生变化时.

在实践中,以下是使用构造函数注入的方法:

public class TestInheritanceBinding {
   static class Book {
      final String title;
      @Inject Book(@Named("GeneralTitle") String title) {
         this.title = title;
      }
   }
   static class ChildrensBook extends Book {
      @Inject ChildrensBook(@Named("ChildrensTitle") String title) {
         super(title);
      }
   }
   static class ScienceBook extends Book {
      @Inject ScienceBook(@Named("ScienceTitle") String title) {
         super(title);
      }
   }

   @Test
   public void bindingWorked() {
      Injector injector = Guice.createInjector(new AbstractModule() {
         @Override protected void configure() {
            bind(String.class).
            annotatedWith(Names.named("GeneralTitle")).
            toInstance("To Kill a Mockingbird");
            bind(String.class).
            annotatedWith(Names.named("ChildrensTitle")).
            toInstance("Alice in Wonderland");
            bind(String.class).
            annotatedWith(Names.named("ScienceTitle")).
            toInstance("On the Origin of Species");
         }
      });
      Book generalBook = injector.getInstance(Book.class);
      assertEquals("To Kill a Mockingbird", generalBook.title);
      ChildrensBook childrensBook = injector.getInstance(ChildrensBook.class);
      assertEquals("Alice in Wonderland", childrensBook.title);
      ScienceBook scienceBook = injector.getInstance(ScienceBook.class);
      assertEquals("On the Origin of Species", scienceBook.title);
   }
}

Answer 2

你最好的选择可能是用不同的参数注释编写子类构造函数——比如

class ChildrensBook extends Book {
  @Inject ChildrensBook (@AliceInWonderland String title) {
     super(title);
  }
}