Spring — Core Container | Code Factory

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Create Java Project

• Open Eclipse
• Go to File -> New -> Other… -> Java Project
• Create IOC-CoreTest 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">
	</bean>
</beans>

Test.java

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

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;
/**
 * @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);
	}
}

Output:

Dec 11, 2020 2:09:26 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

• In spring.xml if you open any tag and does not close it then you get parser exception. Example: open <bean> tag and don’t close it, now run Client.java
  — In console you can see org.xml.sax.SAXParseException exception
• If you define any unformed tag then also you get parser exception. Example: lets define <codefactory></codefactory>, now run Client.java
  — You can open and close tag then still you will get org.xml.sax.SAXParseException exception because it is not defined in dtd file.
• We not define any scope in bean spring.xml so it will create only single instance. BeanFactory will create instance on first request.