Question

I can load a grammar file in to my java project (in netbeans) and generate/build my lexer and parser classes, load them via reflection and then parse what I need to parse.

What I would like is a simple example of redirecting the results from the generate/build of the lexer and parser to a string so that I can put the errors to a popup like JOptionPane.
Just like ANTLRworks does when you do CTRL-R (in windows at least) showing Error(123) grammar.g:100:12: …Warning…etc…

Now I am already using a DiagnosticCollector but this does not always enough details as the CTRL-r in ANTLRworks does. The idea being the user corrects the grammar in order to correct the mistake.

Here’s a snippet of my code

            Tool tool = new Tool(new String[]{userDir + grammarPath + grammarName + ".g"});
            //tool.setOutputDirectory(userDir + grammarPath );
            tool.process();
            if(tool.getNumErrors()>0) {
                errors=true;
                unableToLoadGrammar_AddLine("1. Detected "+tool.getNumErrors()+" Error(s)"+tool.toString()+"\n");
            }

Thanks

Answer 1

Call org.antlr.tool.ErrorManager‘s setErrorListener method:

public class ToolTest {
    public static void main(String[] args) {


        org.antlr.Tool tool = new org.antlr.Tool(new String[] { "GrammarWithErrors.g" });

        final ArrayList<String> messages = new ArrayList<String>();

        ErrorManager.setErrorListener(new ANTLRErrorListener() {

            @Override
            public void warning(Message msg) {
                messages.add("Warning: " + msg.toString());
            }

            @Override
            public void info(String msg) {
                messages.add("Info: " + msg.toString());
            }

            @Override
            public void error(ToolMessage msg) {
                messages.add("Tool Error: " + msg.toString());
            }

            @Override
            public void error(Message msg) {
                messages.add("General Error: " + msg.toString());
            }
        });

        tool.process();

        System.out.println("Done processing...");

        for (String msg : messages) {
            System.out.println(msg);
        }
    }
}

Passing a bad grammar to the code above produces the following output:

Done processing...
General Error: error(100): GrammarWithErrors.g:1:14: syntax error: antlr: MismatchedTokenException(74!=52)
Tool Error: error(150):  grammar file GrammarWithErrors.g has no rules
General Error: error(100): GrammarWithErrors.g:82:7: syntax error: assign.types: NoViableAltException(0@[])

Note that Tool still operates directly on System.err and System.out. If you want to handle everything coming out of Tool, you’ll have to call System.setErr and System.setOut as well.