Spring — Hello World Example | Code Factory

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Create Java Project

• Open Eclipse
• Go to File -> New -> Other… -> Java Project
• Create HelloWorld project
• Right click on project -> Build Path -> Configure Build Path -> Libraries tab -> Add External JARs
  — commons-logging-X.X.jar
  — spring-beans-X.X.X.jar
  — spring-context-X.X.X.jar
  — spring-core-X.X.X.jar
• * You can find dtd information from spring-beans-X.X.X.jar -> org -> springframework -> beans -> factory -> xml -> spring-beans.dtd (line no 36 & 37)

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="com.codeFactory.beans.Test" />
</beans>

Test.java

package com.codeFactory.beans;
/**
 * @author code.factory
 *
 */
public class Test {
	public Test() {
		System.out.println("Test.Test()");
	}
	public void hello() {
		System.out.println("Hello World...");
	}
}

Client.java

package com.codeFactory.test;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
import com.codeFactory.beans.Test;
/**
 * @author code.factory
 *
 */
public class Client {
	public static void main(String... args) {
		/* find xml */
		Resource r = new ClassPathResource("com/codeFactory/resources/spring.xml");
		
		/* load xml into container */
		BeanFactory factory = new XmlBeanFactory(r);
		
		/* create test class object */
		Object o1 = factory.getBean("t");
		Object o2 = factory.getBean("t");
		Object o3 = factory.getBean("t");
		
		System.out.println(o1 == o2);
		System.out.println(o1 == o3);
		
		Test t = (Test) o1;
		t.hello();
	}
}

Output:

Dec 10, 2020 7:50:50 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [com/codeFactory/resources/spring.xml]
Test.Test()
true
true
Hello World...

• IOC container will create one singleton object. In above example you can see that instead of calling factory.getBean(“t”) multiple times still we have only single object.

Test.Test()
true
true
Hello World...

• In <bean></bean> if we don’t sprcify anything then scope is singleton. If we define scope=”prototype” then it will create new object on every request.

Test.Test()
Test.Test()
Test.Test()
false
false
Hello World...