HelloServiceAutoConfiguration.java

package hello;

import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
@ConditionalOnClass(HelloService.class)
@EnableConfigurationProperties(HelloProperties.class)
public class HelloServiceAutoConfiguration {

	@Bean
	@ConditionalOnMissingBean
	public HelloService helloService() {
		return new ConsoleHelloService();
	}

}