Getting different output in a Spring project

[pramod talekar]

Hello,

Could you please tell me why I'm getting a different output in the below Spring 3.0 program :-

package com.springinaction.springidol;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Tester {

	public static void main(String[] args) {
		
		ApplicationContext context = new ClassPathXmlApplicationContext("spring-idol.xml");
		
		Performer performer = (Performer) context.getBean("sing");
		performer.Perform();
	}
	
}

package com.springinaction.springidol;

public class Instrumentalist implements Performer{
	
	private String song;
	private Instrument instrument;
	
	public Instrument getInstrument() {
		return instrument;
	}
	
	public String getSong() {
		return song;
	}
	
	public Instrumentalist(String song, Instrument inst) {
		this.song = song;
		this.instrument = inst;
	}
	
	@Override
	public void Perform() {
		// TODO Auto-generated method stub
		System.out.println("Playing    " + getSong() );
		System.out.println(getInstrument());
		instrument.play();
	}
}

package com.springinaction.springidol;

public interface Performer {

	public void Perform();
}

package com.springinaction.springidol;

public interface Instrument {

	public void play();
}

package com.springinaction.springidol;

public class Player implements Instrument{
	
	private String instrument;
	
	@Override
	public void play() {
		// TODO Auto-generated method stub
		System.out.println("IN class Player, Playing " + this.instrument );
	}
		
	public Player(String instrument) {
		this.instrument = instrument;
	}
}

This is my xml configuration file spring-idol.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN" "http://www.springframework.org/dtd/spring-beans-2.0.dtd">

<beans>

	<bean id="sing" class="com.springinaction.springidol.Instrumentalist">
		<!-- <property name="song" value="Yeh Dil..."></property> -->
		<constructor-arg  value=" DYNAMITE ..."></constructor-arg>
		<constructor-arg  ref="player"></constructor-arg>
		
		<!-- <property name="instrument" value="Guitar..."></property> -->
	</bean>
	
	<bean id="player" class="com.springinaction.springidol.Player">
	<constructor-arg value="VIOLIN....."></constructor-arg>
	</bean>
	
</beans>

I'm getting the below output :-

Playing DYNAMITE ...
using ...com.springinaction.springidol.Player@171bbc9
IN class Player, Playing VIOLIN.....


I was expecting "using VIOLIN......" in the second line, but don't know why it's different.
I cleaned up the project and rebuilt but no use..

Please advise.

[Mark Spritzler]

Because

System.out.println(getInstrument());

Is going to call toString on your Instrument, and toString default implementation in Object is to print the Object. Which in your instance of instrument at that moment is

com.springinaction.springidol.Player@171bbc9

Try overriding toString to print "violin"

Mark

[pramod talekar]

Ah ... !!!
Thanks Mark.

[pramod talekar]

Try overriding toString to print "violin"

Hey Mark,

Since "VIOLIN.." is defined in the conf file and which might change in future, what can I write during the @Override of toString() ?
or can I avoid this @Override and still get 'VIOLIN' printed using Spring ?

[Mark Spritzler]

Also, you didn't post all the code. How does "using…" printout. Where is that code?

The only other way besides overriding toString is to cast your Instrument to the actual type to get to the String instrument variable value. But that would remove you from coding to an interface which is a best practice to always code to an interface. So for me the only option you have and what should be done is overriding toString. Look at Object classes implementation of toString and you will see why you got your value.

Mark

[pramod talekar]

Hey Mark,

I just added System.out.println("using " + getInstrument()); to the original System.out.println(getInstrument()); to make it more meaningful. Sorry for missing it out over here..

The only other way besides overriding toString is to cast your Instrument to the actual type to get to the String instrument variable value.

You mean to say just like the other variable song which I written?
I thought so and that's why made it bit different to see what would happen..
Besides, I also changed few things like adding setters/getter and and trying out different things in xml file , but couldn't overcome that problem.
Will try out the overriding method and let you know.

Thanks a lot.

[Mark Spritzler]

The main point I am saying here, at this point. Is that your issue is a plain Java issue, that you would have using these classes without Spring. Spring isn't causing the Instrument's toString method printing the object reference.

Mark