Spring aop报空指针错误

我在做Spring in action 那本书中Injecting non-Spring beans的例子，该配的包都配了，还是报空指针错误，希望高手指点一下，谢谢。 <aop:spring-configured/>
    <bean id="pianist" class="com.springinaction.springidol.Instrumentalist" abstract="true">
        <property name="song" value="Chopsticks"/>
        <property name="instrument">
            <bean class="com.springinaction.springidol.Piano"/>
        </property>
    </bean>@Configurable("pianist")
public class Instrumentalist implements Performer {
    public Instrumentalist() {
    }    public void perform() throws PerformanceException {
        System.out.print("Playing " + song + " : ");
        instrument.play();    }ApplicationContext ctx = new ClassPathXmlApplicationContext(
                "com/springinaction/springidol/spring-idol.xml");       Instrumentalist pianist = new Instrumentalist();
        pianist.perform();Exception in thread "main" java.lang.NullPointerException
at com.springinaction.springidol.Instrumentalist.perform(Instrumentalist.java:19)
at com.springinaction.springidol.JugglerApp.main(JugglerApp.java:56)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:90)
Playing null :