How do I do a multipart/form file upload with jax-rs?

The key is to leverage the @MultipartForm annotations that comes with RESTEasy. This enables you to define a POJO that contains all the parts of the form and bind it easily.

Take for example the following POJO:

public class FileUploadForm {
    private byte[] filedata;

    public FileUploadForm() {}

    public byte[] getFileData() {
        return filedata;
    }

    @FormParam("filedata")
    @PartType("application/octet-stream")
    public void setFileData(final byte[] filedata) {
        this.filedata = filedata;
    }
}

Now all you need to do is use this POJO in the entity which would look something like this:

@POST
@Path("/upload")
@Consumes("multipart/form-data")
public Response create(@MultipartForm FileUploadForm form) 
{
    // Do something with your filedata here
}