We provide support for using TextMessages and BytesMessages for outgoing messages and TextMessages, BytesMessages and MapMessages for incomming messages.
In JMS Header inspector you can check the Send As BytesMessage option and convert message to BytesMessage.
Also if you provide attachment in request (only the first one) it will be used as payload of the message.
Type of outgoing message folows this logic:
If the content type of the attachment is text, plain or xml then this attachment will be sent as TextMessage, unless you check Send As BytesMessage option, otherwise it will be sent as BytesMessage.
Correspondingly, when receiving a BytesMessage its payload will be checked if it is XML document and show in XML response editor or if not XML shown as a response attachment.
You can receive MapMessage and see it in XML response editor also.
Also we need to mention that you can use Rest Request Test Step and Http Request Test Step to send its first attachment as TexMessage or BytesMessage over JMSendpoint.