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<div style="color: #274e13;">In last couple of tutorials we have seen that the basic features about spring framework as like <b><a href="https://dineshonjava.com/spring-ioc-container/">Spring IoC Container</a>, <a href="https://dineshonjava.com/dependency-injection-in-spring/">Dependency Injection</a>, <a href="https://dineshonjava.com/application-context-in-spring/">ApplicationContext</a>, <a href="https://dineshonjava.com/what-is-bean-factory-in-spring/">BeanFactory</a> </b>etc. In <a href="https://dineshonjava.com/dependency-injection-in-spring/">first chapter</a> we have discussed about <a href="https://dineshonjava.com/dependency-injection-in-spring/">Dependency Injection</a> using an Example of Drawing Class and Shape class. As given below in picture-</div>
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<div class="separator" style="clear: both; text-align: center;"><img title="Coding To Interfaces in Spring" src="https://dineshonjava.com/wp-content/uploads/2012/07/dependencies-injection.jpg" border="0" /></div>
</div>
<p> ;</p>
<div style="color: #274e13;">In above picture we will see that second part name <b><i>Drawing Class Dependent on Shape Class </i></b> Actually shape is not a class Its an interface which implemented by three classes as <b><i>Triangle, Circle &; Rectangle</i></b>.</div>
<p> ;</p>
<div style="color: #274e13;">
<p>In our Drawing Application class(<b>DrawingApp.java</b>) we are using <i><b>draw()</b></i> method of the <i><b>Triangle class</b></i>. As below-</p>
</div>
<pre class="highlight">ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml"); 
Triangle triangle = (Triangle) context.getBean("triangle"); 
triangle.draw(); 
</pre>
<div style="color: #274e13;">
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<p>Here Drawing Application knows that it using <i><b>draw()</b></i> method of Triangle bean. If we want to use the <b><i>draw()</i></b> method of the <b>circle class</b> then we have to write the following code in the Drawing Application-</p>
</div>
<pre class="highlight">ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml"); 
Circle circle= (Circle) context.getBean("circle"); 
circle.draw(); 
</pre>
<div style="color: #274e13;">
<p>If want to use the true power of spring framework then we have to use the <b>coding to interface technique</b>. In <b>coding to interface</b> Drawing Application(<b>DrawingApp.java</b>) does not care about that the <i><b>draw()</b></i> method of which classes is called. Both classes just implements the <i><b>Shape </b></i>interface with one method <i><b>draw()</b></i>. And after that Drawing Class have the following code-</p>
</div>
<pre class="highlight">ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml"); 
Shape shape = (Shape) context.getBean("shape"); 
shape.draw(); 
</pre>
<p>Lets see the full running example about the Coding to interface.<br />
<b><br />
</b> <b>Shape.java</b></p>
<pre class="highlight">package com.dineshonjava.sdnext.interfaceCoding.tutorial; 
 
public interface Shape 
{ 
 void draw(); 
} 
</pre>
<p><b><br />
</b> <b>Triangle.java</b></p>
<pre class="highlight">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()+")"); 
 } 
} 
</pre>
<p><b><br />
</b> <b>Circle.java</b></p>
<pre class="highlight">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()+")"); 
 } 
} 
</pre>
<p><b><br />
</b> <b>Point.java</b></p>
<pre class="highlight">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; 
 } 
} 
</pre>
<p><b><br />
</b> <b>Spring.xml</b></p>
<pre class="highlight"><;beans xmlns:aop="http://www.springframework.org/schema/aop" xmlns:p="http://www.springframework.org/schema/p" xmlns:> 
If every thing is OK then run the following Drawing Application draw a shape using draw() method of shape interface. 
<b> 
</b> <b>DrawingApp.java</b> 
<pre class="highlight">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(); 
 } 
} 
</pre>
<p>Its draw a triangle.</p>
<div style="background-color: #ff99cc; border-width: thin; border: solid;">
<div style="color: blue;"><b>Output:</b></div>
<div style="color: red;">Jul 8, 2012 7:02:58 PM org.springframework.context.support.AbstractApplicationContext prepareRefresh</div>
<div style="color: red;">INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@ab50cd: startup date [Sun Jul 08 19:02:57 IST 2012]; root of context hierarchy</div>
<div style="color: red;">Jul 8, 2012 7:02:58 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions</div>
<div style="color: red;">INFO: Loading XML bean definitions from class path resource [spring.xml]</div>
<div style="color: red;">Jul 8, 2012 7:02:59 PM org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons</div>
<div style="color: red;">INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@14c1103: defining beans [triangle,circle,pointA,pointB,pointC,center]; root of factory hierarchy</div>
<p><b>Drawing Triangle</b><br />
<b>PointA is (0, 0)</b><br />
<b>PointB is (-20, 0)</b><br />
<b>PointC is (20, 0)</b></p>
</div>
<div style="color: #274e13;"><b><br />
</b> <b>If we want draw a circle the execute the following Drawing Application.</b></div>
<p><b><br />
</b> <b>DrawingApp.java</b></p>
<pre class="highlight">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(); 
 } 
} 
</pre>
<div style="color: #274e13;"><b><br />
</b> <b>Its draw a circle.</b></div>
<div style="background-color: #ff99cc; border-width: thin; border: solid;">
<div style="color: blue;"><b>Output:</b></div>
<div style="color: red;">Jul 8, 2012 7:05:11 PM org.springframework.context.support.AbstractApplicationContext prepareRefresh</div>
<div style="color: red;">INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@ab50cd: startup date [Sun Jul 08 19:05:11 IST 2012]; root of context hierarchy</div>
<div style="color: red;">Jul 8, 2012 7:05:11 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions</div>
<div style="color: red;">INFO: Loading XML bean definitions from class path resource [spring.xml]</div>
<div style="color: red;">Jul 8, 2012 7:05:11 PM org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons</div>
<div style="color: red;">INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@14c1103: defining beans [triangle,circle,pointA,pointB,pointC,center]; root of factory hierarchy</div>
<p><b>Circle is drawn of center (10, 10)</b></p>
</div>
</div>
<p> ;</p>
<div style="color: #274e13;">In our <b>enterprise application</b> the coding to interface very necessary &; useful. We are using <b>DAO &; Service layers</b> as interfaces in the <b>enterprise application </b>but its <b>business logic</b> implement these interfaces. If in future you want to change or adding new <b>business logic</b> of <b>enterprise application</b> you does not need to change in the view layer(<b>DAO &; Service layers</b>). You just need add one more class that implements that interface and rewired with spring <b><a href="https://dineshonjava.com/dependency-injection-in-spring/">dependency injection</a></b>.</div>
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<p> ;</p>
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<p> ;</p>
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