gwtupload - File Upload with GWT

1. Download last version of the library: gwtupload-x.x.x.jar and include it in your classpath.

2. Add these libraries to your application: commons-fileupload-1.2.jar, commons-io-1.3.1.jar and log4j.jar

3. Edit your module file: Xxx.gwt.xml.

<module>

  <!-- Include GWTUpload library -->
  <inherits name="gwtupload.GWTUpload"/>
  <!-- Load dinamically predefined styles in the library when the application starts -->
  <stylesheet src="Upload.css"/>
 
  <!-- Change this line with your project's entry-point -->
  <entry-point class="package.Xxx"/>
</module>

4. Edit your web.xml and include your customized servlet (extending ActionUpload and overriding executeAction). Be aware that the servlet provided depends on these libraries: commons-fileupload, commons-io and log4j, so include them in your package.
<context-param>
    <!-- max size of the upload request -->
    <param-name>maxSize</param-name>
    <param-value>3145728</param-value>
  </context-param>
  <context-param>
    <!-- Useful in development mode to slow down the uploads in fast networks.
         Put the number of milliseconds to sleep in each block received in the server.
         false or 0, means don't use slow uploads  -->
    <param-name>slowUploads</param-name>
    <param-value>200</param-value>
  </context-param>

  <servlet>
    <servlet-name>uploadServlet</servlet-name>
    <!-- This is the default servlet, it puts files in session -->
    <servlet-class>xxxxx.server.servlet.UploadServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>uploadServlet</servlet-name>
    <url-pattern>/xxx/upload</url-pattern>
  </servlet-mapping>

5. Create your client application
public class MultipleUploadSample implements EntryPoint {

  // A panel where the thumbnails of uploaded images will be shown
  private FlowPanel panelImages = new FlowPanel();

  public void onModuleLoad() {
    // Attach the image viewer to the document
    RootPanel.get("thumbnails").add(panelImages);
   
    // Create a new uploader panel and attach it to the document
    MultiUploader defaultUploader = new MultiUploader();
    RootPanel.get("default").add(defaultUploader);

    // Add a finish handler which will load the image once the upload finishes
    defaultUploader.addOnFinishUploadHandler(onFinishUploaderHandler);
  }

  // Load the image in the document and in the case of success attach it to the viewer
  private IUploader.OnFinishUploaderHandler onFinishUploaderHandler = new IUploader.OnFinishUploaderHandler() {
    public void onFinish(IUploader uploader) {
      if (uploader.getStatus() == Status.SUCCESS) {

        new PreloadedImage(uploader.fileUrl(), showImage);
       
        // The server sends useful information to the client by default
        UploadedInfo info = uploader.getServerInfo();
        System.out.println("File name " + info.name);
        System.out.println("File content-type " + info.ctype);
        System.out.println("File size " + info.size);

        // You can send any customized message and parse it
        System.out.println("Server message " + info.message);
      }
    }
  };

  // Attach an image to the pictures viewer
  private OnLoadPreloadedImageHandler showImage = new OnLoadPreloadedImageHandler() {
    public void onLoad(PreloadedImage image) {
      image.setWidth("75px");
      panelImages.add(image);
    }
  };
}

6. create your customized servlet
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Hashtable;
import java.util.List;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.io.FilenameUtils;
import org.apache.log4j.Logger;
import gwtupload.server.UploadAction;
import gwtupload.server.exceptions.UploadActionException;

public class UploadServlet extends UploadAction {

 private static final long serialVersionUID = 1L;
 private static Logger log = Logger.getLogger(UploadServlet.class);

 Hashtable<String, String> receivedContentTypes = new Hashtable<String, String>();

 /**
  * Maintain a list with received files and their content types.
  */
 Hashtable<String, File> receivedFiles = new Hashtable<String, File>();
 /**
  * Override executeAction to save the received files in a custom place
  * and delete this items from session. 
  * @return
  */

 @Override
 public String executeAction(HttpServletRequest request, List<FileItem> sessionFiles) throws UploadActionException {
  String response = "";
     int cont = 0;
     System.out.println("In ExecuteAction - UploadServlet Called");
     for (FileItem item : sessionFiles) {
      if (false == item.isFormField()) {
       cont ++;
          try {

           final String UPLOAD_DIRECTORY = "uploads/application/"+now;  
       
           Date date = new Date() ;
           SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy_MM_dd") ;
           String now = dateFormat.format(date);
         
           File uploadsFolder = new File(UPLOAD_DIRECTORY);
           uploadsFolder.mkdirs();
         
           String fileName = item.getName();
         
           // get only the file name not whole path
           if (fileName != null) {
            fileName = FilenameUtils. getName(fileName); // uploaded file filename
           }
         
           File uploadedFile = new File(uploadsFolder, fileName);
           item.write(uploadedFile);
         
           /// Save a list with the received files
           receivedFiles.put(item.getFieldName(), uploadedFile);
           receivedContentTypes.put(item.getFieldName(), item.getContentType());
         
           /// Send a customized message to the client.
           response += uploadedFile;
         
          } catch (Exception e) {
           throw new UploadActionException(e);
          }
      }
     }
    
     /// Remove files from session because we have a copy of them
     removeSessionFileItems(request);
    
     /// Send your customized message to the client.
     return response;
 }
  
 /**
  * Get the content of an uploaded file.
  */
 @Override
 public void getUploadedFile(HttpServletRequest request, HttpServletResponse response) throws IOException {
  String fieldName = request.getParameter(PARAM_SHOW);
     File f = receivedFiles.get(fieldName);
     if (f != null) {
      response.setContentType(receivedContentTypes.get(fieldName));
      FileInputStream is = new FileInputStream(f);
      copyFromInputStreamToOutputStream(is, response.getOutputStream());
     } else {
      renderXmlResponse(request, response, ERROR_ITEM_NOT_FOUND);
     }
   }
  
 /**
  * Remove a file when the user sends a delete request.
  */
 @Override
 public void removeItem(HttpServletRequest request, String fieldName)  throws UploadActionException {
  File file = receivedFiles.get(fieldName);
     receivedFiles.remove(fieldName);
     receivedContentTypes.remove(fieldName);
     if (file != null) {
      file.delete();
     }
 }
}