Spring Java-based Configuration Example

In this post, We will learn about Spring Java-based Configuration Example with a Demo Project

So far We have learned, How we can configure Spring beans using XML configuration files. If you are very much comfortable with XML configuration, then it is really not required to learn how to achieve the same result with Java-based configuration.

The java-based configuration enables us to write most of our Spring configuration without XML but with the help of few Java-based annotations explained in this post.

@Configuration and @Bean Annotations

If We annotate a class with the @Configuration annotation means It indicates that the class can be used by the Spring IoC container as a source of bean definitions. The @Bean annotation tells Spring Container that a method annotated with @Bean will return an object that should be registered as a bean in the Spring Container. The very simplest possible @Configuration class would be as follows −

MySpringConfig.java

package com.kkhindigyan.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import com.kkhindigyan.model.Message;

@Configuration
public class MySpringConfig {
	//Here Spring bean id would be message
	@Bean(name="message")
	public Message getMessage() {
		return new Message();
	}
}

package com.kkhindigyan.config;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

import com.kkhindigyan.model.Message;

@Configuration

public class MySpringConfig {

//Here Spring bean id would be message

@Bean(name="message")

public Message getMessage() {

return new Message();

}

The above config code will be equivalent to the following XML configuration −

<beans>
   <bean id = "message" class = "com.kkhindigyan.model.Message" />
</beans>

<beans>

</beans>

Message.java

package com.kkhindigyan.model;

public class Message {
	
	private Integer messageId;
	private String message;
	
	public Integer getMessageId() {
		return messageId;
	}
	public void setMessageId(Integer messageId) {
		this.messageId = messageId;
	}
	public String getMessage() {
		return message;
	}
	public void setMessage(String message) {
		this.message = message;
	}
}

package com.kkhindigyan.model;

public class Message {

private Integer messageId;

private String message;

public Integer getMessageId() {

return messageId;

}

public void setMessageId(Integer messageId) {

this.messageId = messageId;

}

public String getMessage() {

return message;

}

public void setMessage(String message) {

this.message = message;

}

ClientTest.java

package com.kkhindigyan.org;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.support.AbstractApplicationContext;

import com.kkhindigyan.config.MySpringConfig;
import com.kkhindigyan.model.Message;

public class ClientTest {

	public static void main(String[] args) {
		
		ApplicationContext applicationContext = null;
		
		try {
			
			//Creating Instance of ApplicationContext Spring Container
			applicationContext = new AnnotationConfigApplicationContext(MySpringConfig.class);
			
			//Asking Spring Container to return Spring bean with id "message"
			Object object = applicationContext.getBean("message");
			//Covert Spring bean into your business Object
			Message message = (Message)object;
			message.setMessageId(101);
			message.setMessage("Hello World!!");
			//Print Spring bean state
			System.out.println(message.getMessageId()+"\t"+message.getMessage());
			
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			if (applicationContext != null)
				((AbstractApplicationContext) applicationContext).close();
		}
	}
}

package com.kkhindigyan.org;

import org.springframework.context.ApplicationContext;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import org.springframework.context.support.AbstractApplicationContext;

import com.kkhindigyan.config.MySpringConfig;

import com.kkhindigyan.model.Message;

public class ClientTest {

public static void main(String[] args) {

ApplicationContext applicationContext = null;

try {

//Creating Instance of ApplicationContext Spring Container

applicationContext = new AnnotationConfigApplicationContext(MySpringConfig.class);

//Asking Spring Container to return Spring bean with id "message"

Object object = applicationContext.getBean("message");

//Covert Spring bean into your business Object

Message message = (Message)object;

message.setMessageId(101);

message.setMessage("Hello World!!");

//Print Spring bean state

System.out.println(message.getMessageId()+"\t"+message.getMessage());

} catch (Exception e) {

e.printStackTrace();

}finally {

if (applicationContext != null)

((AbstractApplicationContext) applicationContext).close();

}

If you run ClientTest.java as Java Application then it will give the below output:

101 Hello World!!

That’s all about Spring Java-based Configuration Example

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@Configuration and @Bean Annotations

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