Soap + Rest: Trying to understand differences for selecting fields between the two

Question

I'm working on a Java-Application that integrates with SharePoint. The different SharePoint services are currently requested via the SOAP API. I am now working on an abstraction layer to also integrate with SharePoint 2013 over the REST API. At the moment I have some Problems understanding the differences in querying fields via REST or SOAP (using GetListItems of lists.asmx).

What I learned until now:

1. /_api/web/lists(guid)/items?$select=ID,FileRef I can directly select specific fields
2. Fields of relationships can be selected with $select=Author/EMail&$expand=Author
3. In the REST Version, I have to prefix fields that begin with an underscore by OData_, e.g. $select=OData__UIVersionString
4. The internal name of SharePoint fields is encoded: File Size => File_x0020_Size

What I don't understand:

• Why can't I perform a request with $select=File_x0020_Size? When I try it like this, I get the error "The field or property 'File_x0020_Size' does not exist". But when I go to /_api/web/lists(guid)/fields, the field is clearly available. With the SOAP service, this scenario works without problems.
• Relationships can be expanded (see 2.) in the REST API. How can this be done in the SOAP API? When I add <FieldRef Name="Author" /> to my request, I get something like ows_Author="12;#Username" in the result. But how can I select a specific property, e.g. EMail?

I hope my description of the problem is understandable and that someone can help bring some light into my understanding of SharePoint.

Answer 1

For the REST API, file size is returned in a field called 'Length' when you request a specific file object like with:

/_api/web/getfilebyserverrelativeurl('/<folder name>/<file name>')

http://msdn.microsoft.com/en-us/library/office/dn450841(v=office.15).aspx#bk_FileProperties

EDIT1: re-read question and realize you probably want the size of all the files in a list, which you need to retrieve all the files in a folder for... you would still use Length property though and it is still in bytes

/_api/web/GetFolderByServerRelativeUrl('/<Library Name>')/Files?$select=Length

EDIT2: If you are really asking 'why are these APIs not consistent with each other?' which seems to be what you have clarified -- then good luck finding that answer! You'll probably find many little differences because they were implemented by different (or mostly different) development teams and each has its own external standard that it attempts to implement.

Answer 2

I cannot tell you why you cannot simply select File_x0020_Size, nor can I tell you why you cannot select other fields in REST. I can, however tell you the REST url to retrieve document file sizes:

/_api/web/lists(guid'<guid>')/files?$select=size

Answer 3

I did a lot of testing today and found out that all the fields I can't select are so called Managed Metadata Columns. And these unfortunately can't be selected in a list query with the REST API.

Answer 4

My answer comes in a little bit late, but you can select the file size in your REST query with $select=FileSizeDisplay.