TemplateStringEvaluator.java 文件源码

public static String evaluate(String templateString, Map<String, Object> environment) {
    final Scanner s = new Scanner(templateString);
    // TODO: This is a hack that fails if a string literal contains "}"
    // TODO: It's because i couldn't be bothered nesting grammars.
    s.useDelimiter("((?!\\\\)\\$\\{)|(})");

    StringBuilder ret = new StringBuilder();
    boolean isInsideExpr = templateString.startsWith("${");
    while(s.hasNext()) {
        final String str = s.next();

        if (isInsideExpr) {
            final JsLikeExpressionLexer lexer = new JsLikeExpressionLexer(CharStreams.fromString(str));
            final CommonTokenStream tokenStream = new CommonTokenStream(lexer);
            final JsLikeExpressionParser parser = new JsLikeExpressionParser(tokenStream);


            final TemplateStringEvaluatorVisitor visitor = new TemplateStringEvaluatorVisitor(environment);

            ret.append(parser.expression().accept(visitor).toString());
        } else {
            ret.append(str);
        }

        isInsideExpr = !isInsideExpr;
    }

    return ret.toString();
}