Ways to Register Beans into the Spring Container

In Spring development, beans must be managed by the container. This article summarizes several ways to register a bean.

@Configuration + @Bean

Define a @Configuration class and declare a @Bean method returning the bean instance.

@Configuration
public class MyConfiguration {
    @Bean
    public Person person() {
        Person person = new Person();
        person.setName("spring");
        return person;
    }
}

@Component + @ComponentScan

Annotate the class with @Component and enable scanning via @ComponentScan on a configuration class.

@Component
public class Person {
    private String name;
    // getters and setters
}

@ComponentScan(basePackages = "com.springboot.initbean.*")
public class Demo1 {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(Demo1.class);
        Person bean = ctx.getBean(Person.class);
        System.out.println(bean);
    }
}

@Import variations

Three forms: direct class import, ImportSelector, ImportBeanDefinitionRegistrar, and DeferredImportSelector, each allowing custom logic to add beans.

@Import(Person.class)
public class Demo1 {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(Demo1.class);
        Person bean = ctx.getBean(Person.class);
        System.out.println(bean);
    }
}

FactoryBean

Implement FactoryBean to create bean instances, then register the factory as a @Bean.

class PersonFactoryBean implements FactoryBean
{
    @Override
    public Person getObject() throws Exception {
        return new Person();
    }
    @Override
    public Class
getObjectType() {
        return Person.class;
    }
}

@Configuration
public class Demo1 {
    @Bean
    public PersonFactoryBean personFactoryBean() {
        return new PersonFactoryBean();
    }
    // main method omitted for brevity
}

BeanDefinitionRegistryPostProcessor

Implement this post‑processor to programmatically register BeanDefinition objects before the container refreshes.

public class MyBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {
    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
        AbstractBeanDefinition beanDefinition = BeanDefinitionBuilder.rootBeanDefinition(Person.class).getBeanDefinition();
        registry.registerBeanDefinition("person", beanDefinition);
    }
    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
        // no additional processing
    }
}

public class Demo1 {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
        ctx.addBeanFactoryPostProcessor(new MyBeanDefinitionRegistryPostProcessor());
        ctx.refresh();
        Person bean = ctx.getBean(Person.class);
        System.out.println(bean);
    }
}

The article lists five main techniques for adding beans to the Spring container, each accompanied by code examples and explanations.