spring装配bean-自动化

package soundsystem;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component
public class CDPlayer implements MediaPlayer {
  private CompactDisc cd;

  @Autowired
  public CDPlayer(CompactDisc cd) {
    this.cd = cd;
  }

  public void play() {
    cd.play();
  }

}

package soundsystem;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan
public class CDPlayerConfig { 
}

package soundsystem;

public interface CompactDisc {
  void play();
}

package soundsystem;

public interface MediaPlayer {

  void play();

}

package soundsystem;
import org.springframework.stereotype.Component;

@Component
public class SgtPeppers implements CompactDisc {

  private String title = "Sgt. Pepper's Lonely Hearts Club Band";  
  private String artist = "The Beatles";
  
  public void play() {
    System.out.println("Playing " + title + " by " + artist);
  }
  
}

package soundsystem;

import static org.junit.Assert.*;

import org.junit.Rule;
import org.junit.Test;
import org.junit.contrib.java.lang.system.SystemOutRule;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes=CDPlayerConfig.class)
public class CDPlayerTest {

  @Rule
  public final SystemOutRule log = new SystemOutRule().enableLog();
  @Autowired
  private MediaPlayer player;
  
  @Autowired
  private CompactDisc cd;
  
  @Test
  public void cdShouldNotBeNull() {
    assertNotNull(cd);
  }

  @Test
  public void play() {
    player.play();
    assertEquals(
        "Playing Sgt. Pepper's Lonely Hearts Club Band by The Beatles\r\n", 
        log.getLog());
  }

}