[Question] Finding my rt.jar and telling javassist where it is

[marceloslacerda]

I'm trying to make a an agent that injects some code into a jdbc class at runtime in a running tomcat.

The code I'm using to inject my stuff is

ctMethod.insertAfter("System.out.printf(\"JobID: %d\\\n\", cacheJobNumber);")

However I'm getting an error stating that printf not found in java.io.PrintStream

javassist.CannotCompileException: [source error] printf(java.lang.String,java.lang.String) not found in java.io.PrintStream
	at javassist.CtBehavior.insertAfter(CtBehavior.java:970)

Since I'm running a springboot app (which its running inside an embedded tomcat) it seems like the classpath isn't being filled with any jars.

Here's how I'm trying to populate the ClassPool

val classPool: ClassPool = ClassPool.getDefault()
classPool.appendPathList(ManagementFactory.getRuntimeMXBean().classPath)
LOGGER.warning("Class path from ManagementFactory ${ManagementFactory.getRuntimeMXBean().classPath}")
val classClassPath = ClassClassPath(this.javaClass)
LOGGER.warning("Class path from ClassClassPath ${classClassPath.toString()}")
classPool.insertClassPath(classClassPath);

Unfortunately neither ManagementFactory nor ClassClassPath is able to provide rt.jar

Do you guys have some suggestion on what should I try?

I'm using:

• kotlin 1.7.10
• javassist 3.29.1-GA
• java 11.0.16 (targeting java 8)

[marceloslacerda]

The issue solved itself when I used the same jvm for the agent and the tomcat application