Guice 简明教程
Google Guice - Binding Annotations
由于我们能够使用其实现绑定一个类型。如果我们希望使用多个实现映射一个类型,我们也可以创建自定义注释。请参阅以下示例以了解此概念。
Create a binding annotation
@BindingAnnotation @Target({ FIELD, PARAMETER, METHOD }) @Retention(RUNTIME)
@interface WinWord {}
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@BindingAnnotation - 标记注释作为绑定注释。
-
@Target - 标记注释的适用性。
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@Retention - 将注释的可用性标记为运行时。
Mapping using binding annotation
bind(SpellChecker.class).annotatedWith(WinWord.class).to(WinWordSpellCheckerImpl.class);
Inject using binding annotation
@Inject
public TextEditor(@WinWord SpellChecker spellChecker) {
this.spellChecker = spellChecker;
}
Complete Example
创建名为 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." );
}
}