Image FIle Transfer

Question

This topic may not be appropriate for the 2D forum, but I couldn't find one that deals with images. Please let me know if there's a more appropriate forum.
I use Java 1.4/JBoss 3.22/Oracle 9i.
I have a swing client that occasionally needs to transfer image files (jpg and dxf) to and from the database across the WAN. The file size is typically 1MB. I use RMI-over-HTTP for EJB communication between the client and server.
I need to figure out a way to transfer the files. The ideal would be to bundle BufferedImages in a transfer object that the session bean hands to the client. But, since BufferedImage is not Serializable I need a different method.
How do people typically do this type of transfer?
I appreciate any ideas you can offer.
Thanks,
--BobC                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   

Answer 1

I'm the original poster.
I've solved the problem of transferring BufferedImages between a client and server using an EJB. I wrote a TransferImage class that wraps the BufferedImage in a byte array, which is serializable. Then I transfer an instance of that object using the bean, and then use readObject() to reconstitute the BufferedImage.
Here is the TransferImage class:
package com.whatever;
import java.awt.image.PixelGrabber;
import java.awt.image.BufferedImage;
import java.awt.*;
import java.io.Serializable;
import java.io.IOException;
* This class allows BufferedImages to be serialized so that they can be tranferred
* using an EJB.
* <p>
* NOTE: System.out.printlns are used for logging rather than Log4j for serialization.
* Author: Bob Carpenter [email protected]
* Date: Feb 4, 2004
public class TransferImage extends Canvas
implements Serializable {
private transient BufferedImage image = null;
private int imageType = BufferedImage.TYPE_INT_BGR;
private Object pix = null;
private int width = 0;
private int height = 0;
* Basic ctor.
* <p>
* NOTE: Creates serializable pix object from image.
* @param image buffered image to be transferred
* @param imageType type of image - see BufferedImage class
public TransferImage(BufferedImage image, int imageType)
throws IOException {
System.out.println("TransferImage.ctor_entry");
this.image = image;
this.imageType = imageType;
writeObject();
System.out.println("TransferImage.exit_entry");
* Writes the image to pix object.
* <p>
* NOTE: Uses PixelGrabber to create pix object.
* @throws IOException
private void writeObject() throws IOException {
System.out.println("TransferImage.writeObject_entry");
try {
PixelGrabber grabber = new PixelGrabber(image, 0, 0, -1, -1, true);
grabber.grabPixels();
this.width = grabber.getWidth();
this.height = grabber.getHeight();
System.out.println("TransferImage.writeObject - width = " +width);
System.out.println("TransferImage.writeObject - height = " +height);
pix = grabber.getPixels();
catch(InterruptedException ex) {
throw new IOException("writeObject - ERROR: " +ex);
System.out.println("TransferImage.writeObject_exit");
* Reads the pix object and creates a BufferedImage from it.
* @throws IOException
public BufferedImage readObject() throws IOException {
System.out.println("TransferImage.readObject_entry");
try {
int[] imgPix = (int[])pix;
System.out.println("TransferImage.readObject - imgPixLength = " +imgPix.length);
image = new BufferedImage(width, height, imageType);
image.setRGB(0, 0, width, height, imgPix, 0, width);
catch (Exception ex) {
System.out.println("TransferImage.readObject - ERROR: " +ex);
System.out.println("TransferImage.readObject_exit");
return image;
* Reads the pix object and returns an array of pixel bytes.
* <p>
* NOTE: Doesn't work
* @throws IOException
public byte[] readPix() throws IOException {
System.out.println("TransferImage.readPix_entry");
// Setup
byte[] result = null;
try {
if(pix == null) throw new Exception("found null pix object");
int[] imgPix = (int[])pix;
int imgPixLen = imgPix.length;
// Convert to bytes - this times out
for(int i=0; i<imgPix.length; i++) {
result = new byte[imgPixLen*4];
int j, shift;
for(j = 0, shift = 24; j < 4; j++, shift -= 8)
result[i] += (byte)(0xFF & (imgPix[i] >> shift));
if(result == null) throw new Exception("not able to read pix object");
System.out.println("TransferImage.readPix - pixArrayLength = " +result.length);
catch (Exception ex) {
System.out.println("TransferImage.readPix - ERROR: " +ex);
System.out.println("TransferImage.readPix_exit");
return result;
// Accessors
* Gets the BufferedImage object.
* @return
public BufferedImage getImage() {
return image;
* Gets height of image in pixels.
* @return
public int getHeight() {
return height;
* Gets width of image in pixels.
* @return
public int getWidth() {
return width;
To use the class do this:
//on client (for example)
BufferedImage bufi = ImageIO.read(new File(<some_filePath>));
TransferImage tbufi = new TransferImage(bufi, BufferedImage.TYPE_INT_BGR);
//send tbufi to backend using something like a session bean and a transfer object
//on backend reconstitute the buffered image
TransferImage tbufi = spVO.getImage(); //spVO is my transfer object
BufferedImage bufi = tbufi.readObject();
I'd like to get readPix() working so that a byte array is returned which can feed directly into a ByteArrayInputStream, which can be useful for things like writing to a BLOB. So, if you figure out how to do that please share it.
Take care,
--BobC