code: protected void initJsonReader() {
  		String readerList = config.getJsonReaders();
  		if (readerList != null) {
  			String[] readers = readerList.split(",");
  			Set<String> supportedReaders = TreeReaderRegistry.getReadersByFormat("json");
  			TreeReader selectedReader = null;
  			for (String reader : readers) {
  				reader = reader.trim().toLowerCase();
  				if (!reader.isEmpty()) {
  					for (String supportedReader : supportedReaders) {
  						int i = supportedReader.lastIndexOf('.');
  						if (i > -1) {
  							supportedReader = supportedReader.substring(i + 1);
  						}
  						if (supportedReader.toLowerCase().contains(reader)) {
  							selectedReader = TreeReaderRegistry.getReader(supportedReader);
  							logger.info("Default JSON deserializer/reader is \"" + selectedReader.getClass() + "\".");
  							TreeReaderRegistry.setReader("json", selectedReader);
  							break;
  						}
  					}
  					if (selectedReader != null) {
  						break;
  					}
  				}
  			}
  		}
  	}
docs: Set global JSON reader API (Jackson, Gson, Boon, FastJson, etc.).