Tomcat 8, Spring Boot, #Configurable LoadTimeWeaving without -javaagent? - spring-boot

Question

I'm trying to setup a #Configurable domain object(not managed by the spring container).
I've got this working by adding the -javaagent:path/to/spring-instrument.jar as a JVM argument but it's not 100% clear to me whether or not this -javaagent MUST be in place. I'm running this on Tomcat 8. I may be misinterpreting the documentation but it seems I may be able to use a another mechanism to accomplish this, in particular this line:
Do not define TomcatInstrumentableClassLoader anymore on Tomcat 8.0 and higher. Instead, let Spring automatically use Tomcat’s new native InstrumentableClassLoader facility through the TomcatLoadTimeWeaver strategy.
Code Samples below:
#SpringBootApplication
#EnableLoadTimeWeaving
public class TestApplication {
public static void main(String[] args) {
SpringApplication.run(TestApplication.class, args);
}
#Bean
public MyService myService(){
return new MyService();
}
}
#Configurable
public class MyDomainObject {
#Autowired
private MyService myService;
public MyService getMyService(){
return myService;
}
}
public class MyService {
private static final Logger log = LoggerFactory.getLogger(MyService.class);
public void test(){
log.info("test");
}
}
So is there a way to get these #Configrable objects woven without specifying the -javaagent? I'd be interested in learning if I can accomplish this when deploying as WAR to a Standalone Tomcat 8 server and/or using the embedded Tomcat 8 server when launching as a 'fat' jar.
As it stands deploying to Stand alone Tomcat 8 server doesn't throw an error but the getMyService() method above returns null. Launching as a fat jar throws the following error during startup:
Caused by: java.lang.IllegalStateException: ClassLoader [sun.misc.Launcher$AppClassLoader] does NOT provide an 'addTransformer(ClassFileTransformer)' method. Specify a custom LoadTimeWeaver or start your Java virtual machine with Spring's agent: -javaagent:org.springframework.instrument.jar
I suppose the real question is how do I Specify a custom LoadTimeWeaver in Tomcat 8? Nothing seems to be automatically happening as the documentation states but again I may be misinterpreting what that means exactly.

Answer 1

you can try this :
#Bean
public InstrumentationLoadTimeWeaver loadTimeWeaver() {
return new InstrumentationLoadTimeWeaver();
}
or
there is a new library that just solves to dynamically setup spring InstrumentationLoadTimeWeaver to enable support for aspects without having to start the JVM with an explicit java agent
<dependency>
<groupId>de.invesdwin</groupId>
<artifactId>invesdwin-instrument</artifactId>
<version>1.0.2</version>
</dependency>
#SpringBootApplication
#EnableLoadTimeWeaving
public class TestApplication{
public static void main(final String[] args) {
DynamicInstrumentationLoader.waitForInitialized(); //dynamically attach java agent to jvm if not already present
DynamicInstrumentationLoader.initLoadTimeWeavingContext(); //weave all classes before they are loaded as beans
SpringApplication.run(TestApplication.class, args); //start application, load some classes
}
}

Answer 2

what about creating your own annotation #MyConfigurable ? so you can do what ever you like when it's methods are called.
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
#Target(ElementType.CONSTRUCTOR)
#Retention(RetentionPolicy.RUNTIME)
public #interface MyConfigurable
{}