Bulk export - easysoa/EasySOA GitHub Wiki
Visually
Using UI
You can manually select the what you want to export (documents, folders, or the whole registry) by clicking on their checkbox in the list view and then on "Add to selection", and from there use the "export" feature to get them as a zip. See http://forum.nuxeo.com/t/4977/ or at the end of the second 0.3 video.
Using custom content automation operation chains
You can use Nuxeo Studio to design a custom content automation operation chain and hook it behind a UI button. This chain could for example query all documents named "*.wsdl" then pack them in a zip, like that.
Using Nuxeo shell
You can use the Nuxeo shell and from there its "import" command
Using a CMIS client
TODO
Programmatically
Native Java API
All of that is done on top of the Nuxeo-builtin Java Import / Export API, available from nuxeo-core-io documented here. To use it, call IODocumentManagerImpl.exportDocuments() by providing it with docRefs (gotten from a query...) or a customDocReader for finer handling. It will in turn create a DocumentTreeReader, a NuxeoArchiveWriter and a Pipe to pipe them both.
Remotely
Using either Content Automation API, CMIS API (see Accessing the soa model remotely).