Coding To Interfaces in Spring

ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
Triangle triangle = (Triangle) context.getBean("triangle");
triangle.draw();

ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
Circle circle= (Circle) context.getBean("circle");
circle.draw();

ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
Shape shape = (Shape) context.getBean("shape");
shape.draw();

Lets see the full running example about the Coding to interface.

Shape.java

package com.dineshonjava.sdnext.interfaceCoding.tutorial;

public interface Shape
{
   void draw();
}

Triangle.java

package com.dineshonjava.sdnext.interfaceCoding.tutorial;

public class Triangle implements Shape
{
 private Point pointA;
 private Point pointB;
 private Point pointC;
 
 /**
  * @param pointA the pointA to set
  */
 public void setPointA(Point pointA) {
  this.pointA = pointA;
 }

 /**
  * @param pointB the pointB to set
  */
 public void setPointB(Point pointB) {
  this.pointB = pointB;
 }

 /**
  * @param pointC the pointC to set
  */
 public void setPointC(Point pointC) {
  this.pointC = pointC;
 }

 public void draw()
 {
System.out.println("Drawing Triangle");
System.out.println("PointA is ("+pointA.getX()+", "+pointA.getY()+")");
System.out.println("PointB is ("+pointB.getX()+", "+pointB.getY()+")");
System.out.println("PointC is ("+pointC.getX()+", "+pointC.getY()+")");
 }
}

Circle.java

package com.dineshonjava.sdnext.interfaceCoding.tutorial;

public class Circle implements Shape
{
 private Point center;

 /**
  * @param center the center to set
  */
 public void setCenter(Point center) 
 {
  this.center = center;
 }

 @Override
 public void draw() 
 {
System.out.println("Circle is drawn of center ("+center.getX()+", "+center.getY()+")");
 }
}

Point.java

package com.dineshonjava.sdnext.interfaceCoding.tutorial;

public class Point
{
 private int x;
 private int y;
 /**
  * @return the x
  */
 public int getX() {
  return x;
 }
 /**
  * @param x the x to set
  */
 public void setX(int x) {
  this.x = x;
 }
 /**
  * @return the y
  */
 public int getY() {
  return y;
 }
 /**
  * @param y the y to set
  */
 public void setY(int y) {
  this.y = y;
 }
}

Spring.xml

<beans xmlns:aop="http://www.springframework.org/schema/aop" xmlns:p="http://www.springframework.org/schema/p" xmlns:security="http://www.springframework.org/schema/security" xmlns:tx="http://www.springframework.org/schema/tx" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.springframework.org/schema/beans" xsi:schemalocation="http://www.springframework.org/schema/beans">
  
<bean class="com.dineshonjava.sdnext.interfaceCoding.tutorial.Triangle" id="triangle">
 <property name="pointA" ref="pointA"></property>
 <property name="pointB" ref="pointB"></property>
 <property name="pointC" ref="pointC"></property>
</bean>
  
<bean class="com.dineshonjava.sdnext.interfaceCoding.tutorial.Circle" id="circle">
 <property name="center" ref="center"></property>
</bean>
  
<bean class="com.dineshonjava.sdnext.interfaceCoding.tutorial.Point" id="pointA">
 <property name="x" value="0"></property>
 <property name="y" value="0"></property>
</bean>
  
<bean class="com.dineshonjava.sdnext.interfaceCoding.tutorial.Point" id="pointB">
 <property name="x" value="-20"></property>
 <property name="y" value="0"></property>
</bean>
  
<bean class="com.dineshonjava.sdnext.interfaceCoding.tutorial.Point" id="pointC">
 <property name="x" value="20"></property>
 <property name="y" value="0"></property>
</bean>
  
<bean class="com.dineshonjava.sdnext.interfaceCoding.tutorial.Point" id="center">
 <property name="x" value="10"></property>
 <property name="y" value="10"></property>
</bean>
</beans>

If every thing is OK then run the following Drawing Application draw a shape using draw() method of shape interface.

DrawingApp.java

package com.dineshonjava.sdnext.interfaceCoding.tutorial;

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

/**
 * @author Dinesh
 *
 */
public class DrawingApp {

 /**
  * @param args
  */
 public static void main(String[] args)
 {
ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
Shape shape = (Shape) context.getBean("triangle");
shape.draw();
 }
}

Its draw a triangle.

DrawingApp.java

package com.dineshonjava.sdnext.interfaceCoding.tutorial;

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

/**
 * @author Dinesh
 *
 */
public class DrawingApp {

 /**
  * @param args
  */
 public static void main(String[] args)
 {
ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
Shape shape = (Shape) context.getBean("circle");
shape.draw();
 }
}

In our enterprise application the coding to interface very necessary & useful. We are using DAO & Service layers as interfaces in the enterprise application but its business logic implement these interfaces. If in future you want to change or adding new business logic of enterprise application you does not need to change in the view layer(DAO & Service layers). You just need add one more class that implements that interface and rewired with spring dependency injection.

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