How to Register Spring Beans at Runtime: A Step‑by‑Step Guide

1. Overview

In this article we learn how to register a Spring Bean at runtime . Sometimes you need to add beans conditionally or programmatically.

2. Spring Bean Registration – BeanDefinitionRegistryPostProcessor

One approach is to use BeanDefinitionRegistryPostProcessor. The ApplicationContext automatically detects BeanFactoryPostProcessor beans and applies them before other beans are created. BeanFactoryPostProcessor is an extension point for customizing bean definitions before instantiation. BeanDefinitionRegistryPostProcessor allows registering additional bean definitions before the regular BeanFactoryPostProcessor detection starts.

2.1 Implement BeanDefinitionRegistryPostProcessor

Create an implementation of BeanDefinitionRegistryPostProcessor and override the postProcessBeanDefinitionRegistry method. The class is annotated with @Component so Spring can scan it.

@Component
public static class BeanRegistration implements BeanDefinitionRegistryPostProcessor {
    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry bdr) throws BeansException {
        // custom registration logic
    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory clbf) throws BeansException {
        // optional bean factory processing
    }
}

2.2 Programmatic Bean Registration

The postProcessBeanDefinitionRegistry method receives the bean definition registry, where you can call registerBeanDefinition with a bean name and a BeanDefinition. Use BeanDefinitionBuilder (available since Spring 2.0) to create a bean definition programmatically.

bdr.registerBeanDefinition(
        "customBean",
        BeanDefinitionBuilder.genericBeanDefinition(CustomBean.class,
                () -> new CustomBean("CustomBeanConstructorArgument"))
                .getBeanDefinition()
);

Another example using the generic builder method:

public static <T> BeanDefinitionBuilder genericBeanDefinition(Class<T> beanClass, Supplier<T> instanceSupplier) {
    // builder implementation
}

@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry bdr) throws BeansException {
    bdr.registerBeanDefinition(
        "customBean",
        BeanDefinitionBuilder.genericBeanDefinition(CustomBean.class,
                () -> new CustomBean("CustomBeanConstructorArgument"))
                .getBeanDefinition()
    );
}

3. Register Bean with ApplicationContextInitializer

Implement ApplicationContextInitializer to run code before the Spring application context is fully created.

public class ProgrammaticApplicationContextInitializer implements ApplicationContextInitializer<GenericApplicationContext> {
    @Override
    public void initialize(GenericApplicationContext applicationContext) {
        applicationContext.registerBean(CustomBean.class, "CustomBean initialization");
    }
}

If you are not using Spring Boot, you can register the initializer manually:

public static void main(String[] args) {
    AnnotationConfigApplicationContext applicationContext =
        new AnnotationConfigApplicationContext(BeanfactoryApplication.class);
    ProgrammaticApplicationContextInitializer initializer = new ProgrammaticApplicationContextInitializer();
    initializer.initialize(applicationContext);
}

With Spring Boot you can add the initializer via the builder:

@Configuration
@EnableAutoConfiguration
@ComponentScan
public class BeanfactoryApplication {
    public static void main(String[] args) {
        new SpringApplicationBuilder(BeanfactoryApplication.class)
            .initializers(new ProgrammaticApplicationContextInitializer())
            .run(args);
    }
}

You can also register the initializer in META-INF/spring.factories:

org.springframework.context.ApplicationContextInitializer=\
com.tedblob.ProgrammaticApplicationContextInitializer

Or add it to web.xml for a Spring Web application:

<context-param>
    <param-name>contextInitializerClasses</param-name>
    <param-value>com.tedblob.ProgrammaticApplicationContextInitializer</param-value>
</context-param>
<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

It can also be set via application properties:

context.initializer.classes=com.tedblob.ProgrammaticApplicationContextInitializer

4. Register Runtime Bean with BeanFactory

You can call registerBean on a BeanFactory or ApplicationContext, but this does not create a bean definition.

AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(BeanfactoryApplication.class);
applicationContext.registerBean(CustomBean.class, "custom");
CustomBean customBean = applicationContext.getBean(CustomBean.class);
System.out.println(customBean.getValue() + "");

5. Register Runtime Bean with BeanDefinitionRegistry

BeanDefinitionRegistry

is the sole interface in Spring’s bean factory package that encapsulates bean definition registration. You can dynamically add or remove bean definitions.

To register a new bean definition:

registry.registerBeanDefinition(beanId, newBeanObj);

To remove an existing bean definition:

registry.removeBeanDefinition(beanId);

Example of removing and then adding a bean at runtime:

AutowireCapableBeanFactory factory = applicationContext.getAutowireCapableBeanFactory();
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) factory;
registry.removeBeanDefinition(beanId);
registry.registerBeanDefinition(beanId, newBeanObj);

6. Summary

We have covered how to register a Spring bean at runtime using several techniques, including BeanDefinitionRegistryPostProcessor, programmatic bean creation with BeanDefinitionBuilder, ApplicationContextInitializer, direct BeanFactory registration, and direct manipulation of BeanDefinitionRegistry. The full source code is available in the GitHub repository linked in the article.