Bytecode Instrumentation

| 2004 JavaOne
SM
Conference | Session 3042 Copyright Hewlett Packard Co., 2004.
17
Creating Instrumentation Hooks (pre-5.0)
• Experience with BCEL and class loaders [McPhail]
• Custom class loader
─ Finds, instruments, and loads class before system class loader
─ System classes (java.* and javax.*) still loaded by the system
class loader
─ Type problem with classes loaded by both class loaders –
ClassCastException
• Hidden classpath
─ Follows delegation model for class loading
─ Requires the classes be found through some mechanism other
than the classpath
─ Does not work if software expects to find classes or resources
in the classpath
─ Remedy by creating class loader with parent set to
getClass().getClassLoader() instead of the system class
loader