How do I get the original text that an antlr4 rule matched?

Question

Using the Java 7 grammar https://github.com/antlr/grammars-v4/blob/master/java7/Java7.g4 I want to find methods with a specific name and then just print out that method. I see that I can use the methodDeclaration rule when I match. So I subclass Java7BaseListener and override this listener method:

@Override public void enterMethodDeclaration(Java7Parser.MethodDeclarationContext ctx) { } 

How do I get the original text out? ctx.getText() gives me a string with all the whitespace stripped out. I want the comments and original formatting.

Answer 1

ANTLR's CharStream class has a method getText(Interval interval) which will return the original source in the give range. The Context object has methods to get the beginning and end. Assuming you have a field in your listener called input which has the CharStream being parsed, you can do this:

    int a = ctx.start.getStartIndex();     int b = ctx.stop.getStopIndex();     Interval interval = new Interval(a,b);     input.getText(interval); 

Answer 2

demo:

SqlBaseParser.QueryContext queryContext = context.query(); int a = queryContext.start.getStartIndex(); int b = queryContext.stop.getStopIndex(); Interval interval = new Interval(a,b); String viewSql = context.start.getInputStream().getText(interval);