transmittable-thread-local | 📌 TransmittableThreadLocal , the missing Java™ std | Architecture library

I have a springboot application which I'm trying to instrument using bytebuddy. I'm running into classpath issues which I'm not able to understand.

Firstly, the following is other literature on this:

https://github.com/raphw/byte-buddy/issues/473

https://github.com/raphw/byte-buddy/issues/87

Unable to instrument apache httpclient using javaagent for spring boot uber jar application

https://github.com/raphw/byte-buddy/issues/109

https://github.com/raphw/byte-buddy/issues/473

https://github.com/raphw/byte-buddy/issues/489

https://github.com/spring-projects/spring-boot/issues/4868

https://github.com/alibaba/transmittable-thread-local/issues/161

Problem is that Spring-boot bundles the application into one uber-jar, which contains other jars inside it

A thing to note here is, that if I run the application using IntelliJ, it doesn't use the uber-jar and runs via main class with a bunch of jars as classpath arguments.

Due to this difference, When running via uber-jar(java -jar target/demo-0.0.1-SNAPSHOT.jar), some classes are not available at the time the Agent runs. The classes are loadable at the time of application main, as spring-boot uses its own classloader, which is created at some time b/w agent and application main methods.

I'll describe the behaviour at various points of time below:

• Thread.currentThread().getContextClassLoader() = Launcher$AppClassLoader
• Agent.class.classLoader = Launcher$AppClassLoader
• Class.forName("org.springframework.web.servlet.HandlerAdapter") => ClassNotFoundException
• Class.forName("javax.servlet.http.HttpServletRequest") => ClassNotFoundException

Both spring and javax classes are not loaded as they are not directly in the classpath as per the App Classloader. It's part of an inner jar, something like app.jar!/BOOT-INF/lib/some.jar App Classloader won't be able to load this.

• Thread.currentThread().getContextClassLoader() = org.springframework.boot.loader.LaunchedURLClassLoader
• DemoApplication.class.classloader = same as above
• Class.forName("org.springframework.web.servlet.HandlerAdapter") => loads successfully
• Same for javax class, loads successfully.

After loading, Class.forName("javax.servlet.http.HttpServletRequest").classLoader is also the same LaunchedURLClassLoader.

I have two classes, SpringBootInterceptor (which contains the intercept method) and SpringBootInterceptorOne (which contains the entry and exit method)