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Using parameterized advice to count how many times a track is played
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| package soundsystem; | |
| import java.util.HashMap; | |
| import java.util.Map; | |
| import org.aspectj.lang.annotation.Aspect; | |
| import org.aspectj.lang.annotation.Before; | |
| import org.aspectj.lang.annotation.Pointcut; | |
| @Aspect | |
| public class TrackCounter{ | |
| private Map<Integer, Integer> trackCounts = new HashMap<Integer, Integer>(); | |
| /** | |
| * The thing to focus on is the args(trackNumber) qualifier in the pointcut expression. | |
| * This indicates that any int argument that is passed into the execution of playTrack() | |
| * should also be passed into the advice. The parametername, trackNumber, also matches | |
| * the parameter in the pointcut method signature. | |
| */ | |
| @Pointcut("execution(* soundsystem.CompactDisc.playTrack(int)) and args(trackNumber)") | |
| public void trackPlayed(int trackNumber){} | |
| @Before("trackPlayed(trackNumber") | |
| public void countTrack(int trackNumber){ | |
| int currentCount = getPlayCount(trackNumber); | |
| trackCounts.put(trackNumber, currentCount + 1); | |
| } | |
| public int getPlayCount(int trackNumber){ | |
| return trackCounts.containsKey(trackNumber) ? trackCounts.get(trackNumber) : 0; | |
| } | |
| } |
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