Spring Hello World, Setter Injection With Primitive Values

Let us see the first program in spring, which is going to be the setter injection with some primitive values…

Files required..

• WelcomeBean.java
• ClientLogic.java [ Our logic ]
• spconfig.xml [ spring configuration file, it can be of any name ]

Mates am going to give you the program directly in the eclipse 🙂

Open Eclipse –> File –> New –> (Select Java project, if not found just click on) Other

Now choose –> java project and click on next

Now it will ask you to give you application name, so give what ever name you want and click finish…

That’s it.., now you will see your application will looks like this..

Of course i have been created the files in java4s package…..
Let us see the program files logic

WelcomeBean.java

package java4s;
public class WelcomeBean {

	   private String message;

	   public void setMessage(String message)
	   {
		   this.message = message;
	   }

	   public void show()
	   {
		   System.out.println(message);
	   }

	}

ClientLogic.java

package java4s;

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;

public class ClientLogic {

	public static void main(String[] args)
	{
		Resource res = new ClassPathResource("spconfig.xml");
		BeanFactory factory = new XmlBeanFactory(res);

		Object o = factory.getBean("id1");
		WelcomeBean wb = (WelcomeBean)o;

		wb.show();

	}

}

spconfig.xml

<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN"
"http://www.springframework.org/dtd/spring-beans-2.0.dtd">

<beans>
<bean id="id1" class="java4s.WelcomeBean">

<property name="message" value="Welcome to spring" />

</bean>
</beans>

Explanation

• see WelcomeBean.java, i have written setter method for the property message (primitive), spring container will inject some value in that property at run time
• In ClientLogic.java first we need to load the configuration file, so we done this at line number 12, so res, contains all the information about the configuration xml.
• And give this res object to BeanFactory [ Spring container ] with XmlBeanFactory, so now factory knows all the beans in the xml file so we can now call any bean with bean id.
• In ClientLogic.java, if we call getBean(“id1”) then internally the spring framework executes the following statements
  

  WelcomeBean wb = new WelcomeBean();
  wb.setMessage(“Welcome to spring”);

• And now will gives WelcomeBean object back [at line number 15,] in the form of Object class object, and i typecast into WelcomeBean class at line number 16
  
• Remember, by default every spring bean is the singleton class.  Spring IOC container makes a spring bean as singleton automatically
• Return type of getBean() is always super class object, which is Object class object
• i have given that primitive type as String, you can use int, float, double what ever you want
• See in spconfig.xml, line number 7 we have written the property element right, here <property />  means we are saying to the spring container that we have written setter method in our bean class [WelcomeBean.java 7 to 9 lines ], in the that property we assigned value as an attribute, which means the setter injection is in the form of primitive values [ may be int, string, float bla bla.. ]

Hope you got this tutorial, if not so please go back and see the basic tutorials first.

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::. About the Author .::
		Sivateja Kandula - Java/J2EE Full Stack Developer Founder of Java4s - Get It Yourself, A popular Java/J2EE Programming Blog, Love Java and UI frameworks. You can sign-up for the Email Newsletter for your daily dose of Java tutorials.