Reading constant from properties file
constant.properties

PointA.PointX=-20
PointA.PointY=0

spring.xml

<beans>
	<bean id="pointA" class="com.mugil.shapes.Point">
		<property name="x" value="${PointA.PointX}"/>
		<property name="y" value="${PointA.PointY}"/>
	</bean>
	<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
		<property name="location" value="constant.properties"></property>
	</bean>
</beans>

Using Interface
spring.xml

<beans>
	<bean id="pointA" class="com.mugil.shapes.Point">
		<property name="x" value="${PointA.PointX}"/>
		<property name="y" value="${PointA.PointY}"/>
	</bean>
	<bean class="com.mugil.shapes.Circle" id="circleId">
		<property name="center" ref="pointA"/>
	</bean>
</beans>

shape.java

public interface Shape { 
	public void drawShape();
}

triangle.java

public class Triangle implements Shape
{
 public void drawShape()
 {
   System.out.println("Shape of Triangle");
 }
}

circle.java

public class Circle implements Shape{
	private Point center;
	
	@Override
	public void drawShape() {
		System.out.println("Shape of Circle ");
		System.out.println("Center of Cirlce "+ getCenter().getX() + " - " + getCenter().getY());
	}

	public Point getCenter() {
		return center;
	}

	public void setCenter(Point center) {
		this.center = center;
	}		
}

The objShape will call the draw method based on the instance referenced at runtime
shape.java

public class DrawingApp {
	public static void main(String[] args)  {
		 ApplicationContext objContext = new ClassPathXmlApplicationContext("spring1.xml");
		Shape objShape =  (Shape)objContext.getBean("circleId");
		objShape.drawShape();
	}
}