code: public List<MessageValidator<? extends ValidationContext>> findMessageValidators(String messageType, Message message) {
          List<MessageValidator<? extends ValidationContext>> matchingValidators = new ArrayList<>();
  
          for (MessageValidator<? extends ValidationContext> validator : messageValidators) {
              if (validator.supportsMessageType(messageType, message)) {
                  matchingValidators.add(validator);
              }
          }
  
          if (matchingValidators.isEmpty() || matchingValidators.stream().allMatch(validator -> DefaultMessageHeaderValidator.class.isAssignableFrom(validator.getClass()))) {
              // try to find fallback message validator for given message payload
              if (message.getPayload() instanceof String &&
                      StringUtils.hasText(message.getPayload(String.class))) {
                  String payload = message.getPayload(String.class).trim();
  
                  if (payload.startsWith("<") && !messageType.equals(MessageType.XML.name())) {
                      matchingValidators = findFallbackMessageValidators(MessageType.XML.name(), message);
                  } else if ((payload.trim().startsWith("{") || payload.trim().startsWith("[")) && !messageType.equals(MessageType.JSON.name())) {
                      matchingValidators = findFallbackMessageValidators(MessageType.JSON.name(), message);
                  } else if (!messageType.equals(MessageType.PLAINTEXT.name())) {
                      matchingValidators = findFallbackMessageValidators(MessageType.PLAINTEXT.name(), message);
                  }
              }
          }
  
          if (matchingValidators.isEmpty() || matchingValidators.stream().allMatch(validator -> DefaultMessageHeaderValidator.class.isAssignableFrom(validator.getClass()))) {
              throw new CitrusRuntimeException("Could not find proper message validator for message type '" +
                      messageType + "', please define a capable message validator for this message type");
          }
  
          if (log.isDebugEnabled()) {
              log.debug(String.format("Found %s message validators for message type: %s", matchingValidators.size(), messageType));
          }
          
          return matchingValidators;
      }
docs: Finds matching message validators for this message type.
  
  @param messageType the message type
  @param message the message object
  @return the list of matching message validators.