Accessing Private Variables in the JVM
In this I’ll discuss a uncommonly used but useful technique of accessing variables and methods which have been declared as private in the JVM, using the Apache Commons Lang library to work around the restriction. The description from the project page reads:
The standard Java libraries fail to provide enough methods for manipulation of its core classes. Apache Commons Lang provides these extra methods.
A couple weeks ago I was working on a project that required parsing some CQL statements. There isn’t a standard parser separate from the Cassandra project at the moment, so I decided to pull in the entirety of cassandra-all from maven central. The parser in Cassandra isn’t really designed to be used as a library. In particular, the org.apache.cassandra.cql3.QueryProcessor has a parseStatement(String) call, but the ParsedStatement that’s returned doesn’t expose any of the private variables via getters. I felt particularly determined for some reason, so I decided to investigate a workaround.