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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?
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In computer-based language recognition, ANTLR (pronounced antler), or ANother Tool for Language Recognition, is a parser generator that uses LL(*) for parsing.
An ANTLR lexer creates a Token object after matching a lexical rule. Each request for a token starts in Lexer. nextToken , which calls emit once it has identified a token. emit collects information from the current state of the lexer to build the token.
ANTLR 4 allows you to define lexer and parser rules in a single combined grammar file. This makes it really easy to get started. To get familiar with working with ANTLR, let's take a look at what a simple JSON grammar would look like and break it down. grammar Json; @header { package com.
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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