TimeSeriesMetricExpression.java 文件源码

/**
 * Read expression from reader.
 *
 * @param reader A reader supplying the input of an expression.
 * @return A TimeSeriesMetricExpression corresponding to the parsed input
 * from the reader.
 * @throws IOException on IO errors from the reader.
 * @throws
 * com.groupon.lex.metrics.timeseries.TimeSeriesMetricExpression.ParseException
 * on invalid expression.
 */
public static TimeSeriesMetricExpression valueOf(Reader reader) throws IOException, ParseException {
    final Logger LOG = Logger.getLogger(TimeSeriesMetricExpression.class.getName());

    class DescriptiveErrorListener extends BaseErrorListener {
        public List<String> errors = new ArrayList<>();

        @Override
        public void syntaxError(Recognizer<?, ?> recognizer, Object offendingSymbol,
                                int line, int charPositionInLine,
                                String msg, org.antlr.v4.runtime.RecognitionException e) {
            LOG.log(Level.INFO, "Parse error: {0}:{1} -> {2}", new Object[]{line, charPositionInLine, msg});
            errors.add(String.format("%d:%d: %s", line, charPositionInLine, msg));
        }
    }

    final DescriptiveErrorListener error_listener = new DescriptiveErrorListener();

    final ExpressionLexer lexer = new ExpressionLexer(CharStreams.fromReader(reader));
    lexer.removeErrorListeners();
    lexer.addErrorListener(error_listener);

    final Expression parser = new Expression(new BufferedTokenStream(lexer));
    parser.removeErrorListeners();
    parser.addErrorListener(error_listener);

    final Expression.ExprContext expr;
    try {
        expr = parser.expr();
    } catch (Exception ex) {
        LOG.log(Level.SEVERE, "parser yielded exceptional return", ex);
        if (!error_listener.errors.isEmpty())
            throw new ParseException(error_listener.errors, ex);
        else
            throw ex;
    }

    if (!error_listener.errors.isEmpty()) {
        if (expr.exception != null)
            throw new ParseException(error_listener.errors, expr.exception);
        throw new ParseException(error_listener.errors);
    } else if (expr.exception != null) {
        throw new ParseException(expr.exception);
    }
    return expr.s;
}