По какой-то причине не создается бин "guitaristOne", в книге возможно опечатка. Выбрасывается исключение IllegalStateException

IllegalStateException: Cannot convert value of type 'com.sun.proxy.$Proxy5 implementing pl.arlou.defaultapp.aop.Singer,org.springframework.aop.SpringProxy,org.springframework.aop.framework.Advised,org.springframework.core.DecoratingProxy' to required type 'pl.arlou.defaultapp.aop.GrammyGuitarist' for property 'guitarist': no matching editors or conversion strategy found.

public class GuitaristDemo {
    public static void main(String[] args) {
        ApplicationContext ctx = new ClassPathXmlApplicationContext("app-context.xml");
        Documentarist guitaristOne = ctx.getBean("guitaristOne", Documentarist.class);
        System.out.println("Documentarist One >>");
        guitaristOne.execute();


    }
}

public interface Singer {
    void sing();
    void talk();
}

public class Guitar {
    private String brand = " Martin";
    public String play(){
        return "G C G C Am D7";
    }
    public String getBrand(){
        return brand;
    }
    public void setBrand(String brand){
        this.brand = brand;
    }
}

public class GrammyGuitarist implements Singer {
    @Override
    public void sing() {
        System.out.println("Gravity is working against me and gravity wants to break me down");
    }

    @Override
    public void talk() {
        System.out.println("Guitarist talking");

    }

    public void sing(Guitar guitar){
        System.out.println("play: " + guitar.play());
    }
    public void rest(){
        System.out.println("zzz");
    }
}

public class Documentarist {
    private GrammyGuitarist guitarist;

    public void execute(){
        guitarist.sing();
        guitarist.talk();
    }
    public void setGuitarist(GrammyGuitarist guitarist){
        this.guitarist = guitarist;
    }
}

public class AuditAdvice  {

    public void before(JoinPoint joinPoint) throws Throwable {
        System.out.println("Executing before method: " + joinPoint.getSignature().getName());
    }
    public void after(JoinPoint joinPoint) throws Throwable {
        System.out.println("Executing after method: " + joinPoint.getSignature().getName());

}
}

Ну и сам XML-файл:

<?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:aop="http://www.springframework.org/schema/aop" xmlns:p="http://www.springframework.org/schema/p"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
    http://www.springframework.org/schema/aop
    http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
    ">

  <!-- We don't need to this; This is required only in annotation based AOP support -->
  <!-- <aop:aspectj-autoproxy /> -->

 <aop:config>
   <aop:pointcut id="singExecution" expression="execution(* pl.arlou.defaultapp.aop.Singer.sing(..))"/>
   <aop:aspect ref="advice">
     <aop:before method="before" pointcut-ref="singExecution"/>
     <aop:after method="after" pointcut-ref="singExecution"/>
   </aop:aspect>

 </aop:config>
  <bean id="advice" class="pl.arlou.defaultapp.aop.AuditAdvice"/>
  <bean id="guitaristOne" class="pl.arlou.defaultapp.aop.Documentarist"
  p:guitarist-ref="johnMayer"/>
    <bean id="johnMayer" class="pl.arlou.defaultapp.aop.GrammyGuitarist"/>
</beans>