The aim of this article is to learn how to dynamically trace/observe running Java applications (JDK 6+) using BTrace without changing the code and configuration params of the applications.
What is BTrace?
BTrace is an open source project that was started in 2007 and was originally owned by two people – A.Sundararajan and K. Balasubramanian. It gained fame thanks to Java One 2008 conference.
BTrace helps us to pinpoint complicated code problems in the application. The problems that can be solved using BTrace include code bugs, unpredictable flows, concurrency problems and performance problems that happen under specific and usually hard to reproduce circumstances.
BTrace dynamically (without restarting application) instruments (changes) bytecode of an application in the way that programmer defines. The goal of the instrumentation is to see what happens in a specific area of the code. If used beyond this scope it may harm applications' flow and therefore is forbidden by a validator.
BTrace dynamically (without restarting application) instruments (changes) bytecode of an application in the way that programmer defines. The goal of the instrumentation is to see what happens in a specific area of the code. If used beyond this scope it may harm applications' flow and therefore is forbidden by a validator.
For example let's try to solve following problem – an important file gets deleted occasionally once a day. We want to find the code that does this. Therefore we would like to change "delete" method of java.io.File and print a stack trace of the calling thread if the file name fits. With BTrace we can do this by writing a short and straightforward Java code.
