Using ApplicationContextAware in Spring

In this chapter we will show you a short hint how you can access your Spring-ApplicationContext from everywhere in your Application.

We'll provide our beans with access to the ApplicationContext object by implementing the ApplicationContextAware interface. We'll also use BeanNameAware interface to get the name of the bean configured in the Spring XML.

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WHY ApplicationContextAware?

Imagine we have an application (e.g. a web or swing-application) which we now want to be Spring-enabled. Ok we add the Spring libraries(spring.jar) and the Configuration-file(spring.xml) and create our Spring-beans. But there are still some old class-files which you can’t use in this way. These files still need access to the Spring-Honeypot where all the goodies exists and you don’t want to redesign your application.

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First create the class "ApplicationContextProvider (Triangle class)". This   class    implements    the ApplicationContextAware. A bean which implements the ApplicationContextAware-interface and is deployed into the context, will be called back on creation of the bean, using the interface’s setApplicationContext(…) method, and provided with a reference to the context, which may be stored for later interaction with the context.

package com.dineshonjava.sdnext.contextAware.tutorial;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanNameAware;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;

public class Triangle implements ApplicationContextAware, BeanNameAware
{
 private Point pointA;
 private Point pointB;
 private Point pointC;
 private ApplicationContext context = null;
 
 /**
  * @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()+")");
 }

 @Override
 public void setApplicationContext(ApplicationContext context) throws BeansException
 {
  this.context = context;
 }

 @Override
 public void setBeanName(String beanName)
 {
  System.out.println("Bean name is: "+beanName);
 }
}

package com.dineshonjava.sdnext.contextAware.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;
 }
}

<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.springframework.org/schema/beans" xsi:schemalocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
 <bean autowire="byName" class="com.dineshonjava.sdnext.contextAware.tutorial.Triangle" id="triangle"></bean>
  
<bean class="com.dineshonjava.sdnext.contextAware.tutorial.Point" id="pointA">
  <property name="x" value="0"></property>
  <property name="y" value="0"></property>
</bean>
  
<bean class="com.dineshonjava.sdnext.contextAware.tutorial.Point" id="pointB">
  <property name="x" value="-20"></property>
  <property name="y" value="0"></property>
</bean>
  
<bean class="com.dineshonjava.sdnext.contextAware.tutorial.Point" id="pointC">
   <property name="x" value="20"></property>
   <property name="y" value="0"></property>
</bean>
</beans>

package com.sdnext.contextAware.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) 
 {
ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
Triangle triangle = (Triangle) context.getBean("triangle");
triangle.draw();
 }
}