Processing a String with ANTLR4

java string migration antlr4
Brad Mace picture Brad Mace · Aug 7, 2013 · Viewed 8.9k times · Source

I'm trying to convert my grammar from v3 to v4 and having some trouble finding all the right pieces.

In v3 to process a String, I used:

public static DataExtractor create(String dataspec) {
    CharStream stream = new ANTLRStringStream(dataspec);
    DataSpecificationLexer lexer = new DataSpecificationLexer(stream);
    CommonTokenStream tokens = new CommonTokenStream(lexer);
    DataSpecificationParser parser = new DataSpecificationParser(tokens);

    return parser.dataspec();
}

How do I change this to work in v4?

Answer

Dimitar II picture Dimitar II · Jun 4, 2017

For ANTLR 4.7 the API was changed a little (ANTLRInputStream is deprecated):

InputStream stream = new ByteArrayInputStream(input.getBytes(StandardCharsets.UTF_8));
lexer.setInputStream(CharStreams.fromStream(stream, StandardCharsets.UTF_8));
parser.setInputStream(new CommonTokenStream(lexer));

Hint: if you want to re-use the parser+lexer instances, call their 'reset()' methods after setting their input streams.

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