where does spring boot set proxy as CGLib [duplicate] - spring

Question

Recently i found spring documentation page that says:
Spring AOP uses either JDK dynamic proxies or CGLIB to create the proxy for a given target object. (JDK dynamic proxies are preferred whenever you have a choice).
If the target object to be proxied implements at least one interface then a JDK dynamic proxy will be used.
But it doesn't seem to be the case in my application. I wanted to write a small benchmark to compare the performance of both types of proxying.
There are two similar classes. Both have one method annotated with the #Transactional annotation. One class implements the interface and the other does not:
#Service
public class Cglib {
#Transactional
public void method() {}
}
public interface Dynamic {
void method();
}
#Service
public class DynamicImpl implements Dynamic {
#Override
#Transactional
public void method() {}
}
And based on the documentation for the first class, a CGLIB proxy should be created, and for the second, a JDK dynamic proxy.
But in my case CGLIB was used for both classes:
#Component
#RequiredArgsConstructor
public class Runner implements ApplicationRunner {
private final Cglib cglib;
private final Dynamic dynamic;
#Override
public void run(ApplicationArguments args) {
System.out.println(cglib.getClass());
System.out.println(dynamic.getClass());
}
}
class com.example.demo.proxy.cglib.Cglib$$EnhancerBySpringCGLIB$$767ff22
class com.example.demo.proxy.dynamic.DynamicImpl$$EnhancerBySpringCGLIB$$20a564d6
There are no additional configurations in the application. Only #SpringBootApplication class generated via spring initializr
Am I doing something wrong? The code was run on Spring Boot 2.7.2 and JDK 17.

Answer 1

That is due to spring-boot autoconfiguation:
#Configuration(proxyBeanMethods = false)
#ConditionalOnBean(TransactionManager.class)
#ConditionalOnMissingBean(AbstractTransactionManagementConfiguration.class)
public static class EnableTransactionManagementConfiguration {
#Configuration(proxyBeanMethods = false)
#EnableTransactionManagement(proxyTargetClass = false)
#ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "false")
public static class JdkDynamicAutoProxyConfiguration {
}
#Configuration(proxyBeanMethods = false)
#EnableTransactionManagement(proxyTargetClass = true)
#ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "true",
matchIfMissing = true)
public static class CglibAutoProxyConfiguration {
}
}
it turns #EnableTransactionManagement(proxyTargetClass = true) (Indicate whether subclass-based (CGLIB) proxies are to be created (true) as opposed to standard Java interface-based proxies (false)) when the property spring.aop.proxy-target-class is not set (matchIfMissing = true)