Spring Annotation-Based Configuration Example

In this article, I will be demonstrating how to configure a standalone Spring application using annotation-based configuration. I will be using Eclipse and Maven. In order to get a basic introduction to Spring, you can check out this article. In order to understand how to configure a standalone Spring application using XML configuration, you can refer to this article. In order to understand how to configure a standalone Spring application using Java configuration, you can refer to this article.

Project Set-up

Step 1 – Create a new Maven Project in Eclipse. You can refer to this article on how to create a Maven project in Eclipse.

Step 2 – Add Spring dependencies to the maven pom file. You can add the following:

<dependencies>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-core</artifactId>
      <version>5.2.2.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>5.2.2.RELEASE</version>
    </dependency>
  </dependencies>

Creating Beans

Create the following bean classes:

MessageDAO:

@Repository
public class MessageDAO {
  
  public String getMessage() {
    return "Hello World";
  }

}

MessageDAO is a simple class that has only one method

MessageService:

@Service
public class MessageService {
  
  private MessageDAO messageDAO;

  public void printMessage() {
    String message = messageDAO.getMessage();
    System.out.println(message);
  }

  public MessageDAO getMessageDAO() {
    return messageDAO;
  }

  public void setMessageDAO(MessageDAO messageDAO) {
    this.messageDAO = messageDAO;
  }

}

MessageService has a method

The

Configuration File

Create a file ApplicationContext.xml in the src/main/resources folder as follows:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="
	 http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context.xsd
	http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
	<context:component-scan base-package="learnjava.demo"/>
</beans>

This ApplicationContext.xml is the spring configuration file.  Since we are using annotation based configuration, the configuration file does not contain any bean definitions as explained here.  Instead, it has the

has the

has the

Writing Main Code

Create a class Main.java with the following code:

ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("ApplicationContext.xml");
MessageService messageService = applicationContext.getBean("messageService", MessageService.class);
messageService.printMessage();

The

So on execution, this code prints the following output:

Hello World

Further Learning

Spring MasterClass
Spring Tutorial For Beginners
Step by Step Spring MVC Tutorial
Spring Framework in Easy Steps

Conclusion

So in this article, we saw a Spring Java annotation configuration example. We saw how to configure a standalone Spring application via annotation-based class configuration.