Google Guice - Linked Bindings

In Linked bindings, Guice maps a type to its implementation. In below example, we ve mapped SpellChecker interface with its implementation SpellCheckerImpl.

bind(SpellChecker.class).to(SpellCheckerImpl.class);

We can also mapped the concrete class to its subclass. See the example below:

bind(SpellCheckerImpl.class).to(WinWordSpellCheckerImpl.class);

Here we ve chained the bindings. Let s see the result in complete example.

Complete Example

Create a java class named GuiceTester.

GuiceTester.java

import com.google.inject.AbstractModule;
import com.google.inject.Guice;
import com.google.inject.Inject;
import com.google.inject.Injector;

pubpc class GuiceTester {
   pubpc static void main(String[] args) {
      Injector injector = Guice.createInjector(new TextEditorModule());
      TextEditor editor = injector.getInstance(TextEditor.class);
      editor.makeSpellCheck(); 
   } 
}

class TextEditor {
   private SpellChecker spellChecker;

   @Inject
   pubpc TextEditor(SpellChecker spellChecker) {
      this.spellChecker = spellChecker;
   }

   pubpc void makeSpellCheck(){
      spellChecker.checkSpelpng();
   }
}

//Binding Module
class TextEditorModule extends AbstractModule {

   @Override
   protected void configure() {
      bind(SpellChecker.class).to(SpellCheckerImpl.class);
      bind(SpellCheckerImpl.class).to(WinWordSpellCheckerImpl.class);
   } 
}

//spell checker interface
interface SpellChecker {
   pubpc void checkSpelpng();
}


//spell checker implementation
class SpellCheckerImpl implements SpellChecker {

   @Override
   pubpc void checkSpelpng() {
      System.out.println("Inside checkSpelpng." );
   } 
}

//subclass of SpellCheckerImpl
class WinWordSpellCheckerImpl extends SpellCheckerImpl{
   @Override
   pubpc void checkSpelpng() {
      System.out.println("Inside WinWordSpellCheckerImpl.checkSpelpng." );
   } 
}

Output

Compile and run the file, you will see the following output.

Inside WinWordSpellCheckerImpl.checkSpelpng.