A crude hack to visualize how OpenJDK matches regular expressions. The output will be an HTML file that allows stepping through the matching process.
./gradlew run
The generated trace will be written to a file report.html in the current
working directory.
Note that running Rexplector was only tested with OpenJDK 8, 9 and 10.
OpenJDK matches regular expressions by transforming the regular expression into
an object tree. Every object in the tree represents a construct of the regular
expression (more or less). These objects are all derived from a common base
class (Pattern.Node) and override the match method for more specialised
behaviour.
Rexplector itself consists out of two parts: a runner (see the Runner class
in src/main/java) and a tracer. The runner is a minimal Java application
that compiles a regular expressen and then matches a given input against the
compiled expression. The tracer then executes the runner in a subprocess and
attaches to it via the Java Debug Interface (JDI in short). Every invocation of
a match method is then intercepted and the arguments as well as the caller
are recorded.
After the runner subprocess exited, a report with a visualization of the calltree is written to a file. The visualization is done with vue.js.
Rexplector is released under the Apache License, Version 2.0 (see the
LICENSE filer or http://www.apache.org/licenses/LICENSE-2.0.html).