package main.java.soundsystem;
public interface CompactDisc {void play();void playTrack(Integer trackNumber);
}

package main.java.soundsystem;import java.util.List;public class BlankDisc implements  CompactDisc{private  String title;private  String artist;private List<String> tracks;public BlankDisc setTitle(String title) {this.title = title;return this;}public BlankDisc setArtist(String artist) {this.artist = artist;return this;}public String getTitle() {return title;}public String getArtist() {return artist;}public void setTracks(List<String> tracks) {this.tracks = tracks;}public void play() {System.out.println("Playing " + title + " by " + artist);if(tracks!=null) {for (String track : tracks) {System.out.println("-Track: " + track);}}}@Overridepublic void playTrack(Integer trackNumber) {System.out.println("Playing "+tracks.get(trackNumber-1));}}

package main.java.soundsystem;public interface Printer {void printCover();
}

package main.java.soundsystem;public class CDPrinter implements Printer {@Overridepublic void printCover() {System.out.println("print CD cover..."+Time);}public String getTime() {return Time;}public CDPrinter setTime(String time) {Time = time;return this;}private String Time;
}

package main.java.soundsystem;import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.DeclareParents;
import org.springframework.stereotype.Component;@Component
@Aspect
public class CDPrinterAspect {@DeclareParents(value = "main.java.soundsystem.CompactDisc+",defaultImpl =CDPrinter.class)public static Printer printer;
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:context="http://www.springframework.org/schema/context"xmlns:aop="http://www.springframework.org/schema/aop"xsi:schemaLocation="http://www.springframework.org/schema/aophttp://www.springframework.org/schema/aop/spring-aop.xsdhttp://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsd"><context:component-scan base-package="main.java.soundsystem"/><aop:aspectj-autoproxy/><bean id="blankDisc"  class="main.java.soundsystem.BlankDisc"><property name="title" value="Sgt. Pepper's Lonely Heart 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></list></property></bean>
</beans>

package main.java.soundsystem;import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;public class main {public static void main(String[] args) {ApplicationContext context = new ClassPathXmlApplicationContext("TrackCounterConfig.xml");CompactDisc cd=(CompactDisc)context.getBean("blankDisc");cd.play();System.out.println("\ncast to Printer\n");((Printer)cd).printCover();}
}

Playing Sgt. Pepper's Lonely Heart Club Band by the Beatles
-Track: Sgt. Pepper's Lonely Hearts Club Band
-Track: With a Little Help from My Friends
-Track: Lucy in the Sky with Diamonds
-Track: Getting Better
-Track: Fixing a Holecast to Printerprint CD cover...null