Dinesh on Java

package com.dineshonjava.sdnext.constructorInjection.tutorial;

/**
 * @author Dinesh Rajput
 *
 */
public class Triangle
{
 private String type;
 private int    height;
 /**
  * @param type the type to set
  */
 /*public void setType(String type) {
  this.type = type;
 }*/
 
 public Triangle(String type)
 {
  this.type = type;
 }
 public Triangle(int height)
 {
  this.height = height;
 }
 public Triangle(String type, int height)
 {
  this.type   = type;
  this.height = height;
 }
 public void draw()
 {
  System.out.println(this.type+" triangle is drawn of height "+this.height);
 }
}

<beans xmlns:aop="http://www.springframework.org/schema/aop" xmlns:p="http://www.springframework.org/schema/p" xmlns:>
The id attribute of the bean element is used to specify the bean name and the class attribute is used to specify the fully qualified class name of the bean. The constructor-arg element with in the bean element is used to inject property value via constructor injection. The index attribute of the constructor-arg element represents the constructor argument sequences which passes to the constructor of the class
such as..  
      Triangle(String type, int height)
at index = 0 argument is type;
and at index = 1 argument is height;
      and so on.
 If any class has one argument constructor then there are no need to specify the index attribute of the bean in the bean configuration in spring. i.e. We can say index attribute used to distinguished to arguments of the constructor. Now second attribute is type of the constructor-arg it is used for type of the arguments of the constructor.
Such as..
          Triangle(String type, int height)
then type = "java.lang.String"
         and type = "int"
and the value attribute specifies the corresponding property value.

Here we set "Equilateral " and "20" for the Triangle bean properties type and height respectively. The following Main class is used to get the Triangle bean from the Spring IoC container and display its value it to the Triangle  .
DrawingApp.java
package com.dineshonjava.sdnext.constructorInjection.tutorial;

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

/**
 * @author Dinesh Rajput
 *
 */
public class DrawingApp 
{
 /**
  * @param args
  */
 public static void main(String[] args) 
 {
 //Triangle triangle = new Triangle();
 //BeanFactory factory =new XmlBeanFactory(new FileSystemResource("spring.xml"));
 ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
 Triangle triangle = (Triangle) context.getBean("triangle");
 triangle.draw();
  }
}

Now we run this example the following output on the console.

Output:
Jun 20, 2012 12:12:25 AM org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@145d068: startup date [Wed Jun 20 00:12:25 IST 2012]; root of context hierarchy
Jun 20, 2012 12:12:25 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [spring.xml]
Jun 20, 2012 12:12:26 AM org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@14c1103: defining beans [triangle]; root of factory hierarchy
Equilateral triangle is drawn of height 20

package com.sdnext.constructorInjection.tutorial;

/**
 * @author Dinesh Rajput
 *
 */
public class Triangle
{
 private String type;
 private int    height;
 /**
  * @param type the type to set
  */
 public void setType(String type) {
  this.type = type;
 }
 
        /**
  * @param height the height to set
  */
 public void setHeight(String height) {
  this.height= height;
 }
 
 public void draw()
 {
  System.out.println(this.type+" triangle is drawn of height "+this.height);
 }
}

<beans xmlns:aop="http://www.springframework.org/schema/aop" xmlns:p="http://www.springframework.org/schema/p" xmlns:>
The id attribute of the bean element is used to specify the bean name and the class attribute is used to specify the fully qualified class name of the bean. The property element with in the bean element is used to inject property value via setter injection. The name attribute of the property element represents the bean attribute and the value attribute specifies the corresponding property value.

Here we set "Equilateral " and "20" for the Triangle bean properties type and height respectively. The following Main class is used to get the Triangle bean from the Spring IoC container and display its value it to the Triangle  .
 
DrawingApp.java
package com.dineshonjava.sdnext.constructorInjection.tutorial;

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

/**
 * @author Dinesh Rajput
 *
 */
public class DrawingApp 
{
 /**
  * @param args
  */
 public static void main(String[] args) 
 {
 //Triangle triangle = new Triangle();
 //BeanFactory factory =new XmlBeanFactory(new FileSystemResource("spring.xml"));
 ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
 Triangle triangle = (Triangle) context.getBean("triangle");
 triangle.draw();
  }
}

Now we run this example the following output on the console.

Output:
Jun 20, 2012 12:12:25 AM org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@145d068: startup date [Wed Jun 20 00:12:25 IST 2012]; root of context hierarchy
Jun 20, 2012 12:12:25 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [spring.xml]
Jun 20, 2012 12:12:26 AM org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@14c1103: defining beans [triangle]; root of factory hierarchy
Equilateral triangle is drawn of height 20

pubic class Triangle{
   private int height;
   private String type;
   private double area;
   ...
   ...
}

pubic class Triangle{
   private Point pointA;
   private Point pointB;
   private Point pointC;
   ...
   ...
}

pubic class Point{
   private int X;
   private int Y;
   ...
   ...
}

Lets see with the example.  
Triangle.java

package com.dineshonjava.sdnext.injectingObject.tutorial;

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

Point.java

package com.dineshonjava.sdnext.injectingObject.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;
 }
}

Here we define the Point class with two properties int x, int y. Actually Point class is also a bean which is as a property of the Triangle bean. Now we will configure both beans to the configuration file(spring.xml).
spring.xml

<beans xmlns:aop="http://www.springframework.org/schema/aop" xmlns:p="http://www.springframework.org/schema/p" xmlns:>
The id attribute of the bean element is used to specify the bean name and the class attribute is used to specify the fully qualified class name of the bean. The property element with in the bean element is used to inject property value via setter injection. The name attribute of the property element represents the bean attribute and the ref attribute specifies the reference of another bean or id of the bean element (Point)  corresponding property.

Here we set "pointA", "pointB" and "pointC" properties name for the Triangle bean with ref id of another bean (Point) "pointA", "pointB" and "pointC" (these id name may be different such like "point1", "point2" and "point3") respectively. Now "pointA" is the id of bean element of one Point class and so on. The following Main class is used to get the Triangle bean from the Spring IoC container and display its value it to the Triangle  .
 

DrawingApp.java
package com.dineshonjava.sdnext.injectingObject.tutorial;

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

/**
 * @author Dinesh Rajput
 *
 */
public class DrawingApp 
{
 /**
  * @param args
  */
 public static void main(String[] args) 
 {
  //BeanFactory factory =new XmlBeanFactory(new FileSystemResource("spring.xml"));
  ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
  Triangle triangle = (Triangle) context.getBean("triangle");
  triangle.draw();
 }
}
 

Output:
Jun 23, 2012 12:30:25 PM org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@ab50cd: startup date [Sat Jun 23 12:30:25 IST 2012]; root of context hierarchy
Jun 23, 2012 12:30:26 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [spring.xml]
Jun 23, 2012 12:30:26 PM org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@14c1103: defining beans [triangle,zeroPoint,Point2,Point3]; root of factory hierarchy
PointA is (0, 0)

PointB is (-20, 0)

PointC is (20, 0)