simple working example of AOP Introduction

amy

Hello, world!

I'm trying to understand how to use AOP Introductions.  A simple yet complete and working example would help me tremendously.  

Here is my toy application (getter amp; setters not shown for brevity):

Car.java

Code:
public Class Car #123;
   private boolean fourDoor;   //getter amp; setter

#125;
I would like to introduce an attribute to hold a string for the paint color in my Car objects.  My understanding so far is that I need to create an interface for the attribute I want to add:

PaintColor.java

Code:
public interface PaintColor #123;
   public String getColor#40;#41;;   public void setColor#40;String color#41;;

#125;
Then I need to implement the interface by extending the DelegatingIntroductionInterceptor:

PaintColorMixin.java

Code:
import org..aop.support.DelegatingIntroductionInterceptor;

public class PaintColorMixin extends DelegatingIntroductionInterceptor #123;
   private String color;   //getter amp; setter

#125;
Here is my spring config file:

CarApp.xml

Code:
...snip xml stuff...
lt;beansgt;   lt;bean id=quot;carTargetquot;  classquot;Carquot; singleton=quot;falsequot;gt;lt;/beangt;
   lt;bean id=quot;paintColorMixinquot; class=quotaintColorMixinquot; singleton=quot;falsequot;gt;lt;/beangt;
   lt;bean id=quot;paintColorAdvisorquot; class=quot;org..aop.support.DefaultIntroductionAdvisorquot; singleton=quot;falsequot;gt;       lt;constructor-arggt;lt;ref bean=quot;paintColorMixinquot;gt;       lt;/constructor-arggt;   lt;/beangt;
   lt;bean id=quot;carquot;  class=quot;org..aop.framework.ProxyFactoryBeanquot;gt;       lt;property name=quot;proxyTargetClassquot;gt; lt;valuegt;truelt;/valuegt; lt;/propertygt;       lt;property name=quot;singletonquot;gt; lt;valuegt;falselt;/valuegt; lt;/propertygt;       lt;property name=quot;proxyInterfacesquot;gt; lt;valuegtaintColorlt;/valuegt; lt;/propertygt;       lt;property name=quot;paintColorAdvisorquot;gt; lt;valuegt;paintColorAdvisorlt;/valuegt; lt;/propertygt;       lt;property name=quot;targetquot;gt; lt;value ref=quot;carTargetquot; lt;/propertygt;   lt;/beangt;
lt;beansgt;
The paintColorAdvisor property of the car bean seems suspicious.  The value suggested in Spring In Action pp. 119 recommends quot;lt;listgt;lt;valuegt;servletActionlt;/valuegt;lt;/listgt;quot;.

I'm not confident in my configuration, and I'm at a loss for how I'm supposed to use the enhanced car object in client code.

Any nudge (or mule kick) in the right direction is greatly appreciated.

Best regards,
Tony

At a glance I can see...

Code:
public class PaintColorMixin extends DelegatingIntroductionInterceptor #123;
should implement PainColor

Code:
public class PaintColorMixin extends DelegatingIntroductionInterceptor implements PaintColor  #123;A simple yet complete and working example would help me tremendously

Try this:

Code:
package introductions;

public class Car #123;#125;

Code:
package introductions;

public interface PaintColor #123;   public String getColor#40;#41;;   public void setColor#40;String color#41;;
#125;

Code:
package introductions;

import org..aop.support.DelegatingIntroductionInterceptor;

public class PaintColorMixin extends DelegatingIntroductionInterceptor   implements PaintColor #123;   private String color = quot;Not Setquot;;   public String getColor#40;#41; #123;return color;#125;   public void setColor#40;String color#41; #123;this.color = color;#125;
#125;

Code:
lt;!DOCTYPE beans PUBLIC quot;-//SPRING//DTD BEAN//ENquot; quot;from#58;//  lt;bean id=quot;carTargetquot; class=quot;introductions.Carquot; singleton=quot;falsequot;gt;lt;/beangt;
   lt;bean id=quot;paintColorMixinquot; class=quot;introductions.PaintColorMixinquot; singleton=quot;falsequot;gt;lt;/beangt;
   lt;bean id=quot;paintColorAdvisorquot; class=quot;org..aop.support.DefaultIntroductionAdvisorquot; singleton=quot;falsequot;gt;       lt;constructor-arggt;lt;ref bean=quot;paintColorMixinquot;/gt;       lt;/constructor-arggt;   lt;/beangt;
   lt;bean id=quot;carquot; class=quot;org..aop.framework.ProxyFactoryBeanquot;gt;       lt;property name=quot;proxyTargetClassquot;gt; lt;valuegt;truelt;/valuegt; lt;/propertygt;       lt;property name=quot;interceptorNamesquot;gt;lt;listgt;    lt;valuegt;paintColorAdvisorlt;/valuegt;lt;/listgt;       lt;/propertygt;       lt;property name=quot;targetquot;gt; lt;ref bean=quot;carTargetquot;/gt; lt;/propertygt;   lt;/beangt;
lt;/beansgt;

Code:
package introductions;

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

public class IntroductionDriver #123;
   public static void main#40;String#91;#93; args#41; #123;       ApplicationContext ctx = new ClassPathXmlApplicationContext#40;    quot;/introductions/introductions.xmlquot;#41;;
       Car car = #40;Car#41; ctx.getBean#40;quot;carquot;#41;;       PaintColor carColor = #40aintColor#41; car;
       // test interfaces       System.out.println#40;quot;Is Car?#58; quot; + #40;car instanceof Car#41;#41;;       System.out.println#40;quot;Is PaintColor?#58; quot; + #40;car instanceof PaintColor#41;#41;;
       // test is modified implementation       System.out.println#40;quot;Get color#58; quot; + carColor.getColor#40;#41;#41;;       carColor.setColor#40;quot;Bluequot;#41;;       System.out.println#40;quot;Get color#58; quot; + carColor.getColor#40;#41;#41;;       carColor.setColor#40;quot;Redquot;#41;;       System.out.println#40;quot;Get color#58; quot; + carColor.getColor#40;#41;#41;;   #125;
#125;Thank you, katentim.  That's just what I needed.  It's working great