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javaregex

Using Regex to generate Strings rather than match them

I am writing a Java utility that helps me to generate loads of data for performance testing. It would be really cool to be able to specify a regex for Strings so that my generator spits out things that match this.

Is something out there already baked that I can use to do this? Or is there a library that gets me most of the way there?

Solution

  • Firstly, with a complex enough regexp, I believe this can be impossible. But you should be able to put something together for simple regexps.

    If you take a look at the source code of the class java.util.regex.Pattern, you'll see that it uses an internal representation of Node instances. Each of the different pattern components have their own implementation of a Node subclass. These Nodes are organised into a tree.

    By producing a visitor that traverses this tree, you should be able to call an overloaded generator method or some kind of Builder that cobbles something together.