I recently did this using Spring Web MVC and Apache Commons FileUpload:
import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import org.apache.commons.fileupload.*;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.io.FilenameUtils;
import org.apache.commons.lang.StringUtils;
import org.apache.log4j.Logger;
(...)
    @RequestMapping(method = RequestMethod.POST)
    public ModelAndView uploadFile(HttpServletRequest request, HttpServletResponse response) {
        ModelAndView modelAndView = new ModelAndView("view");
        if (ServletFileUpload.isMultipartContent(request)) {
            handleMultiPartContent(request);
        }
        return modelAndView;
    }
    private void handleMultiPartContent(HttpServletRequest request) {
        ServletFileUpload upload = new ServletFileUpload();
        upload.setFileSizeMax(2097152); // 2 Mb
        try {
            FileItemIterator iter = upload.getItemIterator(request);
            while (iter.hasNext()) {
                FileItemStream item = iter.next();
                if (!item.isFormField()) {
                    File tempFile = saveFile(item);
                    // process the file
                }
            }
        }
        catch (FileUploadException e) {
            LOG.debug("Error uploading file", e);
        }
        catch (IOException e) {
            LOG.debug("Error uploading file", e);
        }
    }
    private File saveFile(FileItemStream item) {
        InputStream in = null;
        OutputStream out = null;
        try {
            in = item.openStream();
            File tmpFile = File.createTempFile("tmp_upload", null);
            tmpFile.deleteOnExit();
            out = new FileOutputStream(tmpFile);
            long bytes = 0;
            byte[] buf = new byte[1024];
            int len;
            while ((len = in.read(buf)) > 0) {
                out.write(buf, 0, len);
                bytes += len;
            }
            LOG.debug(String.format("Saved %s bytes to %s ", bytes, tmpFile.getCanonicalPath()));
            return tmpFile;
        }
        catch (IOException e) {
            LOG.debug("Could not save file", e);
            Throwable cause = e.getCause();
            if (cause instanceof FileSizeLimitExceededException) {
                LOG.debug("File too large", e);
            }
            else {
                LOG.debug("Technical error", e);
            }
            return null;
        }
        finally {
            try {
                if (in != null) {
                    in.close();
                }
                if (out != null) {
                    out.close();
                }
            }
            catch (IOException e) {
                LOG.debug("Could not close stream", e);
            }
        }
    }
This saves the uploaded file to a temp file.
If you don't need all the low-level control over the upload, it is much simpler to use the CommonsMultipartResolver:
<!-- Configure the multipart resolver -->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <property name="maxUploadSize" value="2097152"/>
</bean>
An example form in the jsp:
<form:form modelAttribute="myForm" method="post" enctype="multipart/form-data">
    <form:input path="bean.uploadedFile" type="file"/>
</form>
The uploadedDocument in the bean is of the type org.springframework.web.multipart.CommonsMultipartFile and can be accessed direcly in the controller (the multipartResolver automatically parses every multipart-request)