5

I'm trying to analyze Java source files with Clojure but I couldn't find a way to do that.

First, I thought using Eclipse AST plugin(by copying necessary JAR's to my Clojure project) but I gave up after seeing Eclipse AST's API(visitor based walker).

Then I've tried creating a Java parser with ANTLR. I can only find one Java 1.6 grammar for ANTLR( http://openjdk.java.net/projects/compiler-grammar/antlrworks/Java.g ) and it doesn't compile with latest ANTLR(here's the errors I'm getting ).

Now I have no idea how can I do that. At worst I'll try to go with Eclipse AST.

Does anyone know a better way to parse Java files with Clojure?

Thanks.

Edit: To clarify my point: I need to find some specific method calls in Java projects and inspect it's parameters(we have multiple definitions of the method, with different type of parameters). Right now I have a simple solution written in Java(Eclipse AST) but I want to use Clojure in this project as much as possible.

sinan
  • 6,809
  • 6
  • 38
  • 67

2 Answers2

4

... and it doesn't compile with latest ANTLR ...

I could not reproduce that.

Using ANTLR v3.2, I got some warnings, but no errors. Using both ANTLR v3.3 and v3.4 (latest version), I have no problems generating a parser.

You didn't mention how you're (trying) to generate a lexer/parser, but here's how it works for me:

java -cp antlr-3.4.jar org.antlr.Tool Java.g

EDIT 1

Here's my output when running the commands:

ls
wget http://www.antlr.org/download/antlr-3.4-complete.jar
wget http://openjdk.java.net/projects/compiler-grammar/antlrworks/Java.g
java -cp antlr-3.4-complete.jar org.antlr.Tool Java.g
ls

enter image description here

As you can see, the .java files of the lexer and parser are properly created.

EDIT 2

Instead of generating a parser yourself (from a grammar), you could use an existing parser like this one (Java 1.5 only AFAIK) and call it from your Clojure code.

Bart Kiers
  • 166,582
  • 36
  • 299
  • 288
  • you can see it from my error log. can you send me the link of your grammar file? – sinan Feb 21 '12 at 12:31
  • Ah, I usually don't follow external code and/or errors. The grammar is the one you posted in your question. And when I move the JAR into a lib-folder and execute `java -cp 'lib/*' org.antlr.Tool Java.g` I again have no problems generating a parser. – Bart Kiers Feb 21 '12 at 12:35
  • you're right. I think I made a mistake while copying contents of Java.g from my browser to a file. Now I just saved link as Java.g and finally generate a parser. Thanks. I'm still open to other alternatives to parsing Java sources. – sinan Feb 21 '12 at 12:40
  • thanks. But now I'm having another problem. Strangely, in the source code of ANTLR generated parser, all methods returning `void` so I can't get any data from Clojure. Do you know anything about this? – sinan Feb 21 '12 at 13:13
  • @sinan, add `output=AST;` to the `options { ... }` in the `.g` file. That way, a `CommonTree` will be returned (you'd possibly need to cast it though). – Bart Kiers Feb 21 '12 at 13:29
2

It depends a bit on what you want to do - what are you hoping to get from the analysis?

If you want to actually compile Java or at least build an AST, then you probably need to go the ANTLR or Eclipse AST route. Java isn't that bad of a language to parse, but you still probably don't want to be reinventing too many wheels..... so you might as well build on the Eclipse and OpenJDK work.

If however you are just interesting in parsing the basic syntax and analysing certain features, it might be easier to use a simpler general purpose parser combinator library. Options to explore:

  • fnparse (Clojure, not sure how well maintained)
  • jparsec (Java, but can probably be used quite easily from Clojure)
mikera
  • 105,238
  • 25
  • 256
  • 415