Spring @Bean Annotation

Let’s say we have a simple class as below.

package com.journaldev.spring;

public class MyDAOBean {

	@Override
	public String toString() {
		return "MyDAOBean"+this.hashCode();
	}
}

Here is a Configuration class where we have defined a @Bean method for MyDAOBean class.

package com.journaldev.spring;

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

@Configuration
public class MyAppConfiguration {

	@Bean
	public MyDAOBean getMyDAOBean() {
		return new MyDAOBean();
	}
}

We can get MyDAOBean bean from Spring context using below code snippet.

AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
context.scan("com.journaldev.spring");
context.refresh();
		
//Getting Bean by Class
MyDAOBean myDAOBean = context.getBean(MyDAOBean.class);

We can specify the @Bean name and use it to get them from spring context. Let’s say we have MyFileSystemBean class defined as:

package com.journaldev.spring;

public class MyFileSystemBean {

	@Override
	public String toString() {
		return "MyFileSystemBean"+this.hashCode();
	}
	
	public void init() {
		System.out.println("init method called");
	}
	
	public void destroy() {
		System.out.println("destroy method called");
	}
}

Now define a @Bean method in the configuration class:

@Bean(name= {"getMyFileSystemBean","MyFileSystemBean"})
public MyFileSystemBean getMyFileSystemBean() {
	return new MyFileSystemBean();
}

We can get this bean from context by using the bean name.

MyFileSystemBean myFileSystemBean = (MyFileSystemBean) context.getBean("getMyFileSystemBean");

MyFileSystemBean myFileSystemBean1 = (MyFileSystemBean) context.getBean("MyFileSystemBean");

We can also specify spring bean init method and destroy method. These methods are called when spring bean is being created and when the context is being closed respectively.

@Bean(name= {"getMyFileSystemBean","MyFileSystemBean"}, initMethod="init", destroyMethod="destroy")
public MyFileSystemBean getMyFileSystemBean() {
	return new MyFileSystemBean();
}

You will notice that “init” method is being called when we invoke the context refresh method and “destroy” method is called when we invoke context close method.

Spring @Bean annotation is widely used in annotation-driven spring applications.

You can download the complete spring project from our GitHub Repository.