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Microsoft Roslyn - compiler as a service is a nice addition to the .NET stack; I was looking for something similar in the Java world. I believe Scala has something similar in the form of compiler plugins but not sure how flexible it is.

The problem I am trying to solve in the Java world is allowing users to write some custom syntax and internally it would get re-wired into a different syntax.

Erik Kaplun
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GammaVega
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  • @bmargulies annotations is way way different from what roslyn is, imo – om-nom-nom Sep 09 '12 at 12:41
  • I agree. that's why I didn't put that remark in an answer. – bmargulies Sep 09 '12 at 12:41
  • @GammaVega it looks like what you need is to develop a *DSL* and I think Java is far from the best in this task. You definitely better to do this in [languages like Scala, Clojure, Groovy, Ruby/JRuby](http://stackoverflow.com/questions/4778560/which-language-that-runs-on-jvm-is-best-suited-for-creating-a-dsl) (thanks to interop with java, you'll still be able to communicate with java part without a lot effort). – om-nom-nom Sep 09 '12 at 12:44

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I've never used Microsoft Roslyn, so I'm not sure about what it provides. But if what you want is to be able to compile classes at runtime, you should look at the JavaCompiler API which has been a part of standard Java since Java SE 6. If that doesn't suit your needs you should probably take a look at Eclipse's ASTParser.

Aleksander Blomskøld
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    Note that it's in JDK, not JRE. A concrete kickoff example can be found in [this answer](http://stackoverflow.com/questions/2946338/how-do-i-programmatically-compile-and-instantiate-a-java-class/2946402#2946402). – BalusC Sep 09 '12 at 12:48
  • Roslyn Link - http://msdn.microsoft.com/en-US/roslyn/ Scala Compiler plugins Link - http://www.scala-lang.org/node/140 Both this language provides a nice expression tree of a compiled code that allows to inspect and re-wire the syntax. – GammaVega Sep 09 '12 at 13:18
  • @GammaVega moreover, upcoming scala release (2.10) contains [*macros* feature](http://scalamacros.org/), that allow you to manipulate AST and rewrite code at compile time without of burden of compiler plugins. – om-nom-nom Sep 09 '12 at 13:23
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Scala will have support for macros in the next release (2.10). You can already play with the milestone releases to check how it works. Basically, they allow to modify AST at compile time. So you can rewrite any piece of Scala in another piece of scala. Check the scalamacros website for examples and doc.

If you want to compile Scala source at runtime, you can look for Eval in the twitter/util project.

paradigmatic
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    In 2.10 we also support runtime compilation out of the box: http://stackoverflow.com/questions/12122939/generating-a-class-from-string-and-instantiating-it-in-scala-2-10/12123609#12123609. – Eugene Burmako Sep 09 '12 at 16:06