SOAP MTOM

SOAP Message Transmission Optimization Mechanism (MTOM) is a standard that is developed by the World Wide Web Consortium (W3C). MTOM describes a mechanism for optimizing the transmission or wire format of a SOAP message by selectively re-encoding portions of the message while still presenting an XML Information Set (Infoset) to the SOAP application.

MTOM uses XML-binary Optimized Packaging (XOP) in the context of SOAP and MIME over HTTP. XOP defines a serialization mechanism for the XML Infoset with binary content that is not only applicable to SOAP and MIME packaging, but to any XML Infoset and any packaging mechanism. It is an alternate serialization of XML that just happens to look like a MIME multipart or related package, with XML documents as the root part. That root part is very similar to the XML serialization of the document, except that base64-encoded data is replaced by a reference to one of the MIME parts, which is not base64 encoded. This reference enables you to avoid the bulk and overhead in processing that is associated with encoding. Encoding is the only way binary data can work directly with XML.

If MTOM mapping generation is disabled, then XOP is disabled. If XOP is disabled, the binary data are not sent by using MIME attachments. Instead, the binary data is base64 encoded as usual.

Without MTOM, the data is encoded in whatever format is described in the schema (base64 or hex) and then is displayed in the XML document. The following example shows a SOAP message with an <xsd:base64Binary> element:

... other transport headers ... 
Content-Type: text/xml; charset=UTF-8

<?xml version="1.0" encoding="UTF-8"?>
   <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
      <soapenv:Header/>
      <soapenv:Body>
         <sendImage xmlns="http://org/apache/axis2/jaxws/sample/mtom">
            <input>
               <imageData>R0lGODl  ... more base64 encoded data ...  KTJk8giAAA7</imageData>
            </input>
         </sendImage>
      </soapenv:Body>
   </soapenv:Envelope>

When MTOM is enabled, the binary data that represents the attachment is included as a MIME attachment to the SOAP message. The following example shows an MTOM-enabled SOAP message with attachment data:

... other transport headers ... 
Content-Type: multipart/related; boundary=MIMEBoundaryurn_uuid_0FE43E4D025F0BF3DC11582467646812; 
type="application/xop+xml"; start="<0.urn:uuid:0FE43E4D025F0BF3DC11582467646813@apache.org>"; 
start-info="text/xml"; charset=UTF-8

--MIMEBoundaryurn_uuid_0FE43E4D025F0BF3DC11582467646812
content-type: application/xop+xml; charset=UTF-8; type="text/xml";
content-transfer-encoding: binary
content-id: 
   <0.urn:uuid:0FE43E4D025F0BF3DC11582467646813@apache.org>


         <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
            <soapenv:Header/>
            <soapenv:Body>
               <ati:sendImage xmlns="http://org/apache/axis2/jaxws/sample/mtom" xmlns:ati="http://org/apache/axis2/jaxws/sample/mtom">
                  <ati:input>
                     <ati:imageData>
                        <xop:Include xmlns:xop="http://www.w3.org/2004/08/xop/include" href="cid:1.urn:uuid:0FE43E4D025F0BF3DC11582467646811@apache.org"/>
                     </ati:imageData>
                  </ati:input>
               </ati:sendImage>
            </soapenv:Body>
         </soapenv:Envelope>
--MIMEBoundaryurn_uuid_0FE43E4D025F0BF3DC11582467646812
content-type: text/plain
content-transfer-encoding: binary
content-id: 
         <1.urn:uuid:0FE43E4D025F0BF3DC11582467646811@apache.org>

... binary data goes here ...
--MIMEBoundaryurn_uuid_0FE43E4D025F0BF3DC11582467646812--

For more information, refer to the official MTOM specification: SOAP Message Transmission Optimization Mechanism