因为我们可以将类型与其实现绑定.如果我们想要映射具有多个实现的类型,我们也可以创建自定义注释.请参阅以下示例以了解该概念.
@BindingAnnotation @Target({ FIELD, PARAMETER, METHOD }) @Retention(RUNTIME) @interface WinWord {}
@BindingAnnotation : 将注释标记为绑定注释.
@Target : 标记注释的适用性.
@Retention : 将注释的可用性标记为运行时.
bind(SpellChecker.class).annotatedWith(WinWord.class).to(WinWordSpellCheckerImpl.class);
@Inject public TextEditor(@WinWord SpellChecker spellChecker) { this.spellChecker = spellChecker; }
创建一个名为GuiceTester的java类.
GuiceTester.java
import java.lang.annotation.Target; import com.google.inject.AbstractModule; import com.google.inject.BindingAnnotation; import com.google.inject.Guice; import com.google.inject.Inject; import com.google.inject.Injector; import java.lang.annotation.Retention; import static java.lang.annotation.RetentionPolicy.RUNTIME; import static java.lang.annotation.ElementType.PARAMETER; import static java.lang.annotation.ElementType.FIELD; import static java.lang.annotation.ElementType.METHOD; @BindingAnnotation @Target({ FIELD, PARAMETER, METHOD }) @Retention(RUNTIME) @interface WinWord {} public class GuiceTester { public 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 public TextEditor(@WinWord SpellChecker spellChecker) { this.spellChecker = spellChecker; } public void makeSpellCheck() { spellChecker.checkSpelling(); } } //Binding Module class TextEditorModule extends AbstractModule { @Override protected void configure() { bind(SpellChecker.class).annotatedWith(WinWord.class) .to(WinWordSpellCheckerImpl.class); } } //spell checker interface interface SpellChecker { public void checkSpelling(); } //spell checker implementation class SpellCheckerImpl implements SpellChecker { @Override public void checkSpelling() { System.out.println("Inside checkSpelling." ); } } //subclass of SpellCheckerImpl class WinWordSpellCheckerImpl extends SpellCheckerImpl { @Override public void checkSpelling() { System.out.println("Inside WinWordSpellCheckerImpl.checkSpelling." ); } }
编译并运行文件,你会看到以下输出.
Inside WinWordSpellCheckerImpl.checkSpelling.