Are there any OData provider SDKs for Ruby or Java?
Unfortunately, they are not.
There are only customers. I have successfully used ruby_odata . It works great with a simple model and provides a mapping for all the basic query parameters, although you need to know the operators (e.g. eq, substringof, etc.).
I came across a more complex model and needed a bit of code tweaking. Easy to pick up: http://odetocode.com/Blogs/scott/archive/2010/07/11/odata-and-ruby.aspx
There are Ruby and Java providers here: http://www.odata.org/developers/odata-sdk
Change The previous link does not work, as indicated below, here is http://www.odata.org/libraries/
There is a project called odata4j in google code that can be used to implement manufacturers and consumers. But I have not tried it yet
Apache Olingo http://olingo.apache.org/ provides the OData Java library that implements Open Data Protocol 2.0, support 4.0 is in beta.
I published Safrano a few days ago. This is a small Ruby-based OData provider platform. This is far from complete and a little experimental, but, nevertheless, it may have some use case.