This topic is about Google Guice – On Demand Injection.
Injection is a process of injecting dependeny into an object. Method and field injections can be used to initialize using exiting object using injector.injectMembers() method. See the example below.
Example
Create a java class named GuiceTester.
GuiceTester.java
import com.google.inject.AbstractModule;
import com.google.inject.Guice;
import com.google.inject.ImplementedBy;
import com.google.inject.Inject;
import com.google.inject.Injector;
public class GuiceTester {
public static void main(String[] args) {
Injector injector = Guice.createInjector(new TextEditorModule());
SpellChecker spellChecker = new SpellCheckerImpl();
injector.injectMembers(spellChecker);
TextEditor editor = injector.getInstance(TextEditor.class);
editor.makeSpellCheck();
}
}
class TextEditor {
private SpellChecker spellChecker;
@Inject
public void setSpellChecker(SpellChecker spellChecker){
this.spellChecker = spellChecker;
}
public TextEditor() { }
public void makeSpellCheck(){
spellChecker.checkSpelling();
}
}
//Binding Module
class TextEditorModule extends AbstractModule {
@Override
protected void configure() {
}
}
@ImplementedBy(SpellCheckerImpl.class)
interface SpellChecker {
public void checkSpelling();
}
//spell checker implementation
class SpellCheckerImpl implements SpellChecker {
public SpellCheckerImpl(){}
@Override
public void checkSpelling() {
System.out.println("Inside checkSpelling." );
}
}
Output
Compile and run the file, you will see the following output.
Inside checkSpelling.
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