推荐订阅源

Boy.java
/*
 * Created on 2004-8-14
 *
 * TODO To change the template for this generated file go to
 * Window - Preferences - Java - Code Style - Code Templates
 */
package com.pp;

/**
 * @author pp
 *
 * TODO To change the template for this generated type comment go to
 * Window - Preferences - Java - Code Style - Code Templates
 */
public interface Kissable {
    public void kiss();
}
Kissable.java
package com.pp;

/**
 * @author pp
 *
 * TODO To change the template for this generated type comment go to
 * Window - Preferences - Java - Code Style - Code Templates
 */
public class Boy implements Kissable{
    public void kiss(){
        System.out.println("KISS");
    }
}
Girl.java
package com.pp;

import org.picocontainer.Startable;

/**
 * @author pp
 *
 * TODO To change the template for this generated type comment go to
 * Window - Preferences - Java - Code Style - Code Templates
 */
public class Girl implements Startable{
    Kissable kissable ;
    public Girl(Kissable kissable){
        this.kissable = kissable;
    }
   
    public void start(){
        kissable.kiss();
    }
   
    public void stop(){}
}

Main.java
package com.pp;

import org.picocontainer.MutablePicoContainer;
import org.picocontainer.defaults.DefaultPicoContainer;

/**
 * @author pp
 *
 * TODO To change the template for this generated type comment go to
 * Window - Preferences - Java - Code Style - Code Templates
 */
public class Main {

    public static void main(String[] args) {
        MutablePicoContainer pico = new DefaultPicoContainer();
        pico.registerComponentImplementation(Boy.class);
        pico.registerComponentImplementation(Girl.class);
        pico.start();
        Girl girl = (Girl)pico.getComponentInstance(Girl.class);
        //girl.kissone();
        pico.stop();
        pico.dispose();
    }    
       
}

如果不用pico来管理，则Main函数看起来是这样的  
   public static void main(String[] args){
        Kissable kissable = new Boy();
        Girl girl = new Girl(kissable);
        girl.start();
    }
也就是说你必须自己来维护Boy对象，

如果在Spring则看起来是这样的
<beans>
     <bean id=“boy“ class=“com.pp.Boy“/>
     <bean id=“girl“ class=“com.pp.Girl“>
             <properties name=“kissable“><ref bean=“boy“/></properties>
     </bean>
</beans>