Single file REST controller with transactional service support, in Groovy using Spring Boot

bootWebTx.groovy

@Grapes(
	@Grab(group='com.h2database', module='h2', version='1.4.190')
)


import org.springframework.transaction.annotation.Transactional
import javax.sql.DataSource;

import org.springframework.jdbc.datasource.embedded.EmbeddedDatabase;
import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseBuilder;
import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseType;

import org.springframework.transaction.support.TransactionSynchronizationManager

@EnableTransactionManagement
@RestController
@groovy.util.logging.Slf4j
class WebApplication 
{
    @Autowired TxService txService;
        
    @RequestMapping("/")
    String home() {
        txService.call();
        return "Hello World\n"
        
    }
    
    @Configuration
    public static class Conf
    {
        @Bean
        public DataSource dataSource() {
            
            // no need shutdown, EmbeddedDatabaseFactoryBean will take care of this
            EmbeddedDatabaseBuilder builder = new EmbeddedDatabaseBuilder();
            EmbeddedDatabase db = builder
                .setType(EmbeddedDatabaseType.H2) //.H2 or .DERBY
                .build();
            return db;
        }
    }
    
    @Service
    @Transactional
    public static class TxService
    {
        public void call()
        {
            log.info "{}", org.springframework.transaction.support.TransactionSynchronizationManager.isActualTransactionActive()
        }
    }
}