[antlr-interest] newbie stringtemplate question

[Pete Siemsen]

I have a working ANTLR 3 parser that recognizes my input files.  Now  
I want to use StringTemplate to make some output.  I stole code from  
the example on page 205 of the book, but I'm having trouble with  
getTemplate.  My translator gives

$ java -cp /Users/siemsen/cimmof2java/target/cimmof2java-1.0- 
SNAPSHOT.jar: \
            /Users/siemsen/antlrplay/antlr-3.0.1/lib/antlr-2.7.7.jar: \
            /Users/siemsen/antlrplay/antlr-3.0.1/lib/antlr-3.0.1.jar: \
            /Users/siemsen/antlrplay/antlr-3.0.1/lib/antlr- 
runtime-3.0.1.jar: \
            /Users/siemsen/antlrplay/antlr-3.0.1/lib/ 
stringtemplate-3.1b1.jar
      cimmof2java cimv216.mof /Users/siemsen/cimmof2java/cimmof2java- 
java.stg /tmp
Exception in thread "main" java.lang.NullPointerException
         at cimmof2java.main(cimmof2java.java:38)
$

Line 38 is the 3rd-from-last line of the program:

import org.antlr.runtime.*;
import org.antlr.stringtemplate.*;
import java.io.*;

public class cimmof2java {
	public static void main(String[] args) throws Exception {

		String inputFileName = args[0];
		String stgFileName = args[1];
		String outputDirectoryName = args[2];

		StringTemplateGroup templates = null;
		// Load template group file cimmof2java.stg into templates variable
		try {
			FileReader groupFileR = new FileReader(stgFileName);
			templates = new StringTemplateGroup(groupFileR);
			groupFileR.close();
		} catch (IOException FileNotFoundException) {
			System.out.println("couldn't open string template group file: " +  
stgFileName);
			System.exit(1);
		}

		// Open an input file stream from the given file name
		CharStream input = new ANTLRFileStream(inputFileName);
		// Create a lexer that feeds from the input file stream
		cimmof2javaLexer lexer = new cimmof2javaLexer(input);
		// Create a stream of tokens fed by the lexer
		CommonTokenStream tokens = new CommonTokenStream(lexer);
		// Create a parser that feeds off the token stream
		cimmof2javaParser parser = new cimmof2javaParser(tokens);
		// Give the parser the string templates
		parser.setTemplateLib(templates);
		// Begin parsing at rule mofSpecification
		cimmof2javaParser.mofSpecification_return retVal =
		    parser.mofSpecification(outputDirectoryName);
		StringTemplate output = (StringTemplate)retVal.getTemplate();
		// Emit the translation
		System.out.println(output.toString());
	}
}

The program reads in my group file, named cimmof2java-java.stg, which  
contains only this:

group cimmof2java;
showclass(clName) ::= "<clName>"

My parser contains these lines among others:

grammar cimmof2java;

options {output=template;}

className
	: Identifier -> showclass(clName={$Identifier.text})
	;

The className rule in the parser definitely gets executed.  What's  
the problem?

-- Pete



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