详解spring切面使用传递给被通知方法的参数

public interface CompactDisc { 
 
  //播放某一个磁道中的歌曲 
  void playTrack(String track); 
 
} 

public class BlankDisc implements CompactDisc { 
 
  private String title; 
  private String artist; 
  private List<String> tracks; 
 
  public void setTitle(String title) { 
    this.title = title; 
  } 
 
  public void setArtist(String artist) { 
    this.artist = artist; 
  } 
 
  public void setTracks(List<String> tracks) { 
    this.tracks = tracks; 
  } 
 
  @Override 
  public void playTrack(String track) { 
    System.out.println("-Track: " + track); 
  } 
 
} 

/** 
 * 切面类的任务：记录每个磁道被播放的次数 
 * Created by Administrator on 2017/12/1. 
 */ 
@Component 
@Aspect 
public class TrackCounter { 
 
  private Map<String, Integer> trackCounts = new HashMap<>(); 
 
  @Pointcut("execution(* chapter04.aop_args.BlankDisc.playTrack(String)) && args(track)") 
  public void trackPlayed(String track) { 
  } 
 
  //在播放前，为该磁道计数 
  @Before("trackPlayed(track)") 
  public void countTrack(String track) { 
    int currentCount = getPlayCount(track); 
    trackCounts.put(track, currentCount + 1); 
  } 
 
  public int getPlayCount(String track) { 
    return trackCounts.containsKey(track) ? trackCounts.get(track) : 0; 
  } 
} 

<context:component-scan base-package="aop_test,chapter04"/> 
 
<bean id="compactDisc" 
   class="chapter04.aop_args.BlankDisc"> 
  <property name="title" value="Sgt. Pepper's Lonely Hearts Club Band" /> 
  <property name="artist" value="The Beatles" /> 
  <property name="tracks"> 
    <list> 
      <value>Sgt. Pepper's Lonely Hearts Club Band</value> 
      <value>With a Little Help from My Friends</value> 
      <value>Lucy in the Sky with Diamonds</value> 
      <value>Getting Better</value> 
      <value>Fixing a Hole</value> 
      <value>She's Leaving Home</value> 
      <value>Being for the Benefit of Mr. Kite!</value> 
      <value>Within You Without You</value> 
      <value>When I'm Sixty-Four</value> 
      <value>Lovely Rita</value> 
      <value>Good Morning Good Morning</value> 
      <value>Sgt. Pepper's Lonely Hearts Club Band (Reprise)</value> 
      <value>A Day in the Life</value> 
    </list> 
  </property> 
</bean> 
 
<!-- 开启aop注解 --> 
<aop:aspectj-autoproxy/> 

@RunWith(SpringJUnit4ClassRunner.class) 
@ContextConfiguration("classpath:applicationContext.xml") 
public class test_aop_args { 
 
  @Autowired 
  CompactDisc cd; 
 
  @Autowired 
  TrackCounter trackCounter; 
 
  @Test 
  public void test(){ 
    cd.playTrack("Sgt. Pepper's Lonely Hearts Club Band"); 
    cd.playTrack("With a Little Help from My Friends"); 
    cd.playTrack("Lucy in the Sky with Diamonds"); 
    cd.playTrack("Sgt. Pepper's Lonely Hearts Club Band"); 
    cd.playTrack("With a Little Help from My Friends"); 
    cd.playTrack("Sgt. Pepper's Lonely Hearts Club Band"); 
 
    System.out.println(trackCounter.getPlayCount("Sgt. Pepper's Lonely Hearts Club Band")); 
    System.out.println(trackCounter.getPlayCount("With a Little Help from My Friends")); 
    System.out.println(trackCounter.getPlayCount("Lucy in the Sky with Diamonds")); 
    System.out.println(trackCounter.getPlayCount("Getting Better")); 
  } 
}