How to generate AST from Java source-code?

Question

As far as I know, the only way to parse Java source-code into an AST (Abstract Syntax Tree) is to use the Java Compiler Tree API: com.sun.source.tree

I have two questions:

1. What JDKs support com.sun.source.tree?
2. Is there a portable replacement that works for all JDKs?

Answer 1

You can possibly take the tools.jar and use it. javac is open source so you can just grab that code (assuming you can deal with the license). Antlr has grammars for Java as well.

Answer 2

Regarding your second question, there are dozens of Java parsers available in addition to Sun's. Here is a small sample:

• Eclipse's org.eclipse.jdt.core.dom package.
• Spoon outputs a very nice annotated parse tree with type information and variable binding (and uses Eclipse's parser internally)
• ANTLR is a parser-generator, but there are grammars for Java available
• javaparser (which I have not used)

My best advice is to try each of them to see which works best for your needs.

Answer 3

I've used Eclipse's AST parser. I found it to be pretty good (well it was part of an Eclipse plug-in so it did make sense to use it). See Exploring Eclipse's ASTParser.

Answer 4

See SD's Java Front End, which is a full featured Java parser built on top of the DMS Software Reengineering Toolkit.

The point of DMS is that it provides a huge variety of useful machinery (attribute grammars, symbol tables, flow analysis, AST manipulation including access and update, as well as source-to-source transformations) to analyze and transform that AST into results and/or modified source code. If you get "just" a Java parser (e.g., JavaCC + Java grammar) you will, IMHO, not be able to do a lot with it. DMS makes it possible to do a lot, without having to invent all that extra machinery yourself.