Spring IOC Container - ApplicationContext

[Rahul Dazz Das]

Every where over the internet, people are professing that IOC approach is better than non IOC approach as it decouple your classes from their dependencies so that the dependencies can be replaced or updated with minimal or no changes. Refer below java programs, one using the IOC approach (file 1, 3 and 4) and another without using the IOC approach (file 1 and 2).

File 1 - Test.java [POJO]

package beans;

public class Test {
	private String salutation;

	public void setSalutation(String salutation) {
	this.salutation = salutation;
	}

	public void hello(String name) {
	System.out.println("Hello "+salutation+""+name);
	}
}

File 2 - Client.java [Without using IOC Container]

package test;

import beans.Test;

public class Client {
	public static void main(String[] args) {
		Test t = new Test();
		t.SetSalutation(“Mr.“);
		t.hello("Rahul");
		
	}
}

File 3 - Client.java [Using IOC Container: ApplicationContext]

package test;

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

import beans.Test;

public class Client {
	public static void main(String[] args) {
		ApplicationContext ap = new ClassPathXmlApplicationContext("resources/spring.xml");
		Test t = (Test)ap.getBean("t");
		t.hello("Rahul");
		((ClassPathXmlApplicationContext)ap).close();
	}
}

File 4 - spring.xml
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN" "http://www.springframework.org/dtd/spring-beans-2.0.dtd"> <beans> <bean id = "t" class = "beans.Test"> <property name = "salutation" value = "Mr."/> </bean> </beans>
No matter whichever approach we follow, we will get the same result "Hello Mr. Rahul". Can anyone please guide as what benefits the IOC approach is offering (in context with the source code shared above) which non IOC approach isn't.

[preetika shukla]

Rahul,

Based on the example which you've given, you can see that Client.java(with out IOC) is very much aware about the type of the objects, which is creating (test here). Say down the line, if you were to have similar functionality for some other class, you will manually go ahead and make the changes in the code to create a new object of it.

Where as in the case of where you're using IOC concept, you can just go ahead change the spring.xml and make no changes in your already written/well tested code.

Also, cases where you're writing test cases for the method, you cannot mock the new object which is getting created inside the method (cases without IOC).

Hope this helps!