BaseStellarProcessor.java 文件源码

/**
 * Parses and evaluates the given Stellar expression, {@code rule}.
 * @param rule The Stellar expression to parse and evaluate.
 * @return The Expression, which can be reevaluated without reparsing in different Contexts and Resolvers.
 */
public static StellarCompiler.Expression compile(final String rule) {
  if (rule == null || isEmpty(rule.trim())) {
    return null;
  }

  ANTLRInputStream input = new ANTLRInputStream(rule);
  StellarLexer lexer = new StellarLexer(input);
  lexer.removeErrorListeners();
  lexer.addErrorListener(new ErrorListener());
  TokenStream tokens = new CommonTokenStream(lexer);
  StellarParser parser = new StellarParser(tokens);

  StellarCompiler treeBuilder = new StellarCompiler(
      ArithmeticEvaluator.INSTANCE,
      NumberLiteralEvaluator.INSTANCE,
      ComparisonExpressionWithOperatorEvaluator.INSTANCE
  );
  parser.addParseListener(treeBuilder);
  parser.removeErrorListeners();
  parser.addErrorListener(new ErrorListener());
  parser.transformation();
  return treeBuilder.getExpression();
}