How to create a FeedItem that has mentions in it with SOAP API?

Question

I am trying to insert feeditems with mentions on a case using SOAP API.

Example - "This case was updated by @John Doe" where John Doe is a user in Salesforce.

How do I make this happen?

I have tried the following

FeedItem fi = new FeedItem();

fi.Body = '@[John Doe](user:*Salesforce User ID*)';

fi.ParentId =  *Case ID*;

fi.Type = 'TextPost';

Answer 1

It doesn't appear to be possible to do anything other than a plain text FeedItem with the SOAP API.

I tried the following directly POSTed to the SOAP API.

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:urn="urn:partner.soap.sforce.com" xmlns:urn1="urn:sobject.partner.soap.sforce.com">
   <soapenv:Header>
      <urn:SessionHeader>
         <urn:sessionId>00D300000000001!AQ0AQMNot_My_Real_Session_Id_Get_Your_Own1miwAs5icUg</urn:sessionId>
      </urn:SessionHeader>
   </soapenv:Header>
   <soapenv:Body>
      <urn:create>
         <!--Zero or more repetitions:-->
         <urn:sObjects>
            <urn1:type>FeedItem</urn1:type>
            <!--Zero or more repetitions:-->
            <urn1:fieldsToNull></urn1:fieldsToNull>
            <urn1:Id></urn1:Id>
            <!--You may enter ANY elements at this point-->
            <urn1:Body>&lt;p&gt;Test Post 4 with mention of @Daniel Ballinger &lt;/p&gt;</urn1:Body>
            <urn1:ParentId>0064000000OXBSI</urn1:ParentId>
            <urn1:IsRichText>true</urn1:IsRichText>
         </urn:sObjects>
      </urn:create>
   </soapenv:Body>
</soapenv:Envelope>

That created a FeedItem record that was identical to on I created directly in the UI with an active Mention of myself. Or at least, identical in how the SOAP Partner API sees the FeedItem records.

I suspect you will need to use the REST based Chatter API to define a richer Feed Item Body with message segments for mentions.

There is an idea - Add @mention to Chatter FeedItem body via Apex Code or AJAX Toolkit, but that appears to have mostly focused on the Apex Chatter integration.