Create Beans programatically with Spring Boot

DemoApplication.java

package com.example;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;
import java.util.stream.Collectors;

@SpringBootApplication
@RestController
@EnableSampleServices
public class DemoApplication {

	@Autowired
	private List<SampleService> services;

	@Autowired @Qualifier("s1")
	private SampleService service1;

    @Autowired @Qualifier("s2")
    private SampleService service2;

	@RequestMapping("/services")
	public String main(){
		return services.stream()
				.map( sampleService -> sampleService.getName())
				.collect(Collectors.joining(", "));
	}

	@RequestMapping("/s1")
	public String service1(){
		return service1.getName();
	}

    @RequestMapping("/s2")
    public String service2(){
        return service2.getName();
    }

	public static void main(String[] args) {
		SpringApplication.run(DemoApplication.class, args);
	}
}

EnableSampleServices.java

package com.example;

import org.springframework.context.annotation.Import;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

@Retention(value = RetentionPolicy.RUNTIME)
@Import(SampleServiceConfiguration.class)
public @interface EnableSampleServices {}

SampleService.java

package com.example;

public class SampleService {

    private String name;

    public SampleService(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }
}

SampleServiceConfiguration.java

package com.example;


import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.type.AnnotationMetadata;

import java.util.Arrays;
import java.util.List;

@Configuration
public class SampleServiceConfiguration implements ImportBeanDefinitionRegistrar {

    private List<String> names = Arrays.asList("s1", "s2", "s3");
    
    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        names.stream().forEach(
                name -> register(registry, name)
        );
    }

    private void register(BeanDefinitionRegistry registry, String name){
        BeanDefinition bd = new RootBeanDefinition(SampleService.class);
        bd.getConstructorArgumentValues()
          .addGenericArgumentValue(name);
        registry.registerBeanDefinition(name, bd);
    }
}

Cool, thanks! I think this is the simplest way I found to create Spring Beans dynamically.

Although for RootBeanDefinition the documentation says to typically use GenericBeanDefinition, like this

    BeanDefinition bd = new GenericBeanDefinition();
    bd.setBeanClassName(SampleService.class.getName());

Note to self: injecting other beans is automatic. You do not need to add ConstructorArgumentValues (like in this example)!!

Hi, is it possible to create a bean dynamically for a class and add annotations on the the created bean. Like:

@InboundChannelAdapter(channel = TransformerChannel.TRANSFORMER_OUTPUT, autoStartup = "false",
        poller = @Poller(value = "customPoller"))
public MessageSource<InputStream> sftpMessageSource() {
    SftpStreamingMessageSource messageSource = new SftpStreamingMessageSource(sftpRemoteFileTemplate,
            null);
    messageSource.setRemoteDirectory(sftpProperties.getSftpDirPath());
    messageSource.setFilter(new SftpPersistentAcceptOnceFileListFilter(new SimpleMetadataStore(),
            "streaming"));
    messageSource.setFilter(new SftpSimplePatternFileListFilter("*.txt"));
    return messageSource;
}

I want to create multiple MessageSource beans dynamically and annotate those beans with the @InboundChannelAdapter. Can you suggest me on how can i achieve that !?

@prinal10 were you able to figure this out?