fix(agent): Append runtime JAR to bootstrap class loader

[dividedmind]

The AppMap runtime JAR must be appended to the bootstrap class loader search path. This ensures that core AppMap runtime classes, such as HookFunctions, are available to all application classes, regardless of the specific class loader (e.g., in web servers like Tomcat). This change fixes NoClassDefFoundError issues for HookFunctions.

This commit also adds a new gretty-tomcat test to verify the fix in a servlet environment.

Another commit adds the ability to run with the whole agent JAR included in the bootstrap classpath in addition to the javaagent. This configuration is not recommended or exactly supported, but a user has found it helpful in working around some quirks in a specific complex classloader environment.

[Copilot]

Pull request overview

This PR fixes NoClassDefFoundError issues for HookFunctions in servlet containers like Tomcat by changing the AppMap runtime JAR to be appended to the bootstrap class loader instead of the system class loader. This ensures core AppMap runtime classes are available to all application classes regardless of their class loader.

Changes:

• Modified Agent.java to use appendToBootstrapClassLoaderSearch instead of appendToSystemClassLoaderSearch
• Added comprehensive gretty-tomcat integration test to verify the fix in a Tomcat servlet environment

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
agent/src/main/java/com/appland/appmap/Agent.java	Changed runtime JAR loading from system class loader to bootstrap class loader and updated explanatory comments
agent/test/gretty-tomcat/build.gradle	Gradle build configuration for the Tomcat test using Gretty plugin with servlet container and AppMap agent setup
agent/test/gretty-tomcat/src/main/java/org/example/HelloServlet.java	Simple servlet implementation to test basic request handling in Tomcat
agent/test/gretty-tomcat/src/main/java/org/example/MyClass.java	Test class with generic type parameters in the instrumented package
agent/test/gretty-tomcat/gretty-tomcat.bats	BATS test script that starts Tomcat server and verifies servlet responds correctly
agent/test/gretty-tomcat/appmap.yml	AppMap configuration specifying the org.example package for instrumentation
agent/test/gretty-tomcat/settings.gradle	Gradle settings file defining the project name
agent/test/gretty-tomcat/src/main/webapp/.keep	Placeholder file to preserve the webapp directory structure in version control

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.