public final void writeString(Reader reader) {
        writeRaw(quote);

        try {
            char[] chars = new char[2048];
            for (; ; ) {
                int len = reader.read(chars, 0, chars.length);
                if (len < 0) {
                    break;
                }

                if (len > 0) {
                    writeString(chars, 0, len, false);
                }
            }
        } catch (Exception ex) {
            throw new JSONException("read string from reader error", ex);
        }

        writeRaw(quote);
    }
If ReferenceDetection has been set, returns the path of the current object, otherwise returns null
@since 2.0.51
@return the path of the current object
core/src/main/java/com/alibaba/fastjson2/JSONWriter.java