It was difficult navigating Alfresco's documentation on the REST API, as there were NO examples, just specs.. and often the specs stated that they were "deprecated". Ultimately I found this document on CMIS and interacting via http. (NOTE: There is a vital typo on page 25 in the cmisra namespace declaration, which causes example to fail.. just remove extraneous slash).
Anyway, I cobbled together an example that demonstrates login, ticket validation, content creation, and logout. This works in the Query Console.. although the base64 module is my own (see prior post on base64 encoding of binary files).
xquery version "1.0-ml";
declare namespace html = "http://www.w3.org/1999/xhtml";
import module namespace json = "http://marklogic.com/xdmp/json" at "/MarkLogic/json/json.xqy";
import module namespace base64 = "base64" at "utility/base64.xqm";
let $string := concat('{ "username":"admin", "password":"admin" }')
let $data := <data>{$string}</data>
let $login := xdmp:http-post("http:/localhost:8080/alfresco/service/api/login",
<options xmlns="xdmp:http">
<data>{$string}</data>
<headers>
<content-type>application/json</content-type>
</headers>
</options>)
let $ticket_xml := json:transform-from-json($login[2])
let $ticket_id := data($ticket_xml//*[local-name() = 'ticket'])
let $uri := concat("http://localhost:8080/alfresco/service/api/login/ticket/",$ticket_id,"?alf_ticket=",$ticket_id)
let $check := xdmp:http-get($uri)
(: if you have a node_id, the following is example of how to retrieve content
let $content_uri := concat("http://localhost:8080/alfresco/service/cmis/i/", $node_id, "/content?alf_ticket=", $ticket_id) :)
let $filedata := base64:encode("/some/path/image.png") (: insert your own base64 here :)
let $content_uri := concat("http://localhost:8080/alfresco/s/cmis/p/path/children", "?alf_ticket=", $ticket_id) (: the "path" is the path after "Company Home" :)
let $atomxml :=
<entry xmlns="http://www.w3.org/2005/Atom"
xmlns:cmisra="http://docs.oasis-open.org/ns/cmis/restatom/200908"
xmlns:cmis="http://docs.oasis-open.org/ns/cmis/core/200908">
<title>image.png</title>
<summary>A sample upload</summary>
<content type="image/png">{$filedata}</content>
<cmisra:object>
<cmis:properties>
<cmis:propertyId propertyDefinitionId="cm:description"><cmis:value>This is the description property</cmis:value></cmis:propertyId>
<cmis:propertyId propertyDefinitionId="cmis:objectTypeId"><cmis:value>cmis:content</cmis:value></cmis:propertyId>
</cmis:properties>
</cmisra:object>
</entry>
let $upload := xdmp:http-post($content_uri,
<options xmlns="xdmp:http">
<data>{concat('<?xml version="1.0" encoding="utf-8"?>',xdmp:quote($atomxml))}</data>
<headers>
<content-type>application/atom+xml</content-type>
</headers>
</options>)
let $logout := xdmp:http-delete($uri)
return ($check,$upload)