File Upload Servlet

FileUploadServlet.java

import java.io.File;
import java.io.IOException;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileItemFactory;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.io.FilenameUtils;

/**
 * Servlet to handle file upload requests
 * 
 * @author faissal.elamraoui
 */
public class FileUploadServlet extends HttpServlet {

	/**
	 * 
	 */
	private static final long serialVersionUID = -5069680745987375734L;

	private static final String UPLOAD_DIRECTORY = "/path/to/upload/directory";

	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		super.doGet(req, resp);
	}

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		// Process only multipart requests
		if (ServletFileUpload.isMultipartContent(req)) {

			// Create the Upload Directory
			File uploadDir = getUploadDir();
			if (!uploadDir.exists()) {
				uploadDir.mkdirs();
			}

			// Create a factory for disk-based file items
			FileItemFactory factory = new DiskFileItemFactory();

			// Create a new file upload handler
			ServletFileUpload upload = new ServletFileUpload(factory);

			// Parse the request
			try {
				List<FileItem> items = upload.parseRequest(req);
				for (FileItem item : items) {
					// Process only file upload - discard other form item types
					if (item.isFormField())
						continue;

					String filename = item.getName();
					// Get only the file name not whole path
					if (filename != null) {
						filename = FilenameUtils.getName(filename);
					}

					File uploadedFile = new File(UPLOAD_DIRECTORY, filename);
					if (uploadedFile.createNewFile()) {
						item.write(uploadedFile);
						resp.setStatus(HttpServletResponse.SC_CREATED);
						resp.flushBuffer();
					} else {
						uploadedFile.renameTo(new File(UPLOAD_DIRECTORY,
								filename + ".old"));
						item.write(uploadedFile);
						resp.setStatus(HttpServletResponse.SC_CREATED);
						resp.flushBuffer();
					}
				}
			} catch (Exception e) {
				resp.sendError(
						HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
						"An error occured while creating the file: "
								+ e.getMessage());
			}

		} else {
			resp.sendError(HttpServletResponse.SC_UNSUPPORTED_MEDIA_TYPE,
					"Request contents type is not supported by the servlet.");
		}
	}

	private File getUploadDir() {
		return new File(UPLOAD_DIRECTORY);
	}
}