Do not expose gocd server class-loader to a plugin

[bdpiprava]

Issue Type

• Bug Report

Summary

GoCD server classloader is being exposed to the plugin and it creates an issue in certain scenarios. One such scenario is when plugins dependencies are using current thread classloader to load the class.

public static Class loadClass(String className) throws ClassNotFoundException {
  try {
      ClassLoader contextClassLoader = Thread.currentThread().getContextClassLoader();
      return contextClassLoader.loadClass(className);
  } catch (Exception e) {
      return Class.forName(className);
  }
}

Above code will load the specified class using GoCD server classloader and from GoCD server dependencies which cause plugins to not work.

Basic environment details

• Go Version: Go Version: 18.7.0 (7118-8494e0df4236380e6b1260f21bea2df13703b64c)

Expected Results

It should load the class from dependencies defined in the plugin, not from the server.

Possible Fix

gocd/plugin-infra/go-plugin-infra/src/main/java/com/thoughtworks/go/plugin/infra/DefaultPluginManager.java

Lines 142 to 148 in 9e996b9

	try {
	return plugin.handle(apiRequest);
	} catch (UnhandledRequestTypeException e) {
	LOGGER.error(e.getMessage());
	LOGGER.debug(e.getMessage(), e);
	throw new RuntimeException(e);
	}

Before submitting a request to plugin set current threads classloader to plugins classloader and revert it back to original classloader at the end.

[maheshp]

Fixed as part of #5011