Google Guice - 构造函数绑定

Guice 提供了一种使用 toConstructor() 方法通过对象的特定构造函数创建绑定的方式。

@Override
protected void configure() {
   try {
      bind(SpellChecker.class)
         .toConstructor(SpellCheckerImpl.class.getConstructor(String.class));
      } catch (NoSuchMethodException | SecurityException e) {
      System.out.println("Required constructor missing");
   } 
} 

请参阅以下完整示例。

完整示例

创建一个名为 GuiceTester 的 java 类。

GuiceTester.java

import com.google.inject.AbstractModule;
import com.google.inject.Guice;
import com.google.inject.Inject;
import com.google.inject.Injector;
import com.google.inject.name.Named;
import com.google.inject.name.Names;

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( SpellChecker spellChecker) {
      this.spellChecker = spellChecker;
   }

   public void makeSpellCheck(){
      spellChecker.checkSpelling();
   } 
}

//Binding Module
class TextEditorModule extends AbstractModule {

   @Override
   protected void configure() {
      try {
         bind(SpellChecker.class)
            .toConstructor(SpellCheckerImpl.class.getConstructor(String.class));
      } catch (NoSuchMethodException | SecurityException e) {
         System.out.println("Required constructor missing");
      } 
      bind(String.class)
         .annotatedWith(Names.named("JDBC"))
         .toInstance("jdbc:mysql://:5326/emp");
   } 
}

//spell checker interface
interface SpellChecker {
   public void checkSpelling();
}

//spell checker implementation
class SpellCheckerImpl implements SpellChecker {

   private String dbUrl;

   public SpellCheckerImpl(){}

   public SpellCheckerImpl(@Named("JDBC") String dbUrl){
      this.dbUrl = dbUrl;
   } 

   @Override
   public void checkSpelling() { 
      System.out.println("Inside checkSpelling." );
      System.out.println(dbUrl); 
   }
}

输出

编译并运行该文件，你将看到以下输出。

Inside checkSpelling.
jdbc:mysql://:5326/emp