Caching images in a JApplet

I have a JApplet here:
http://www.jujubees.org/java_photo_album/photoAlbum.html
the code is coming along well but I have one major problem. The images seem to take for ever to download even with a high speed cable connection (so god only knows how long a dial up would take). What technique can I use to make sure the images are being cached in the web browser? Also is there a way to check and see if the browser has cached a certain image? If you want to see the code then I could post it.

I have a JApplet here:
http://www.jujubees.org/java_photo_album/photoAlbum.htm
the code is coming along well but I have one major
problem. The images seem to take for ever to download
even with a high speed cable connection (so god only
knows how long a dial up would take). What technique
can I use to make sure the images are being cached in
the web browser? Also is there a way to check and see
if the browser has cached a certain image? If you want
to see the code then I could post it.Well you could check to see if the images are being cached by printing out the details of your images, byte size and so on. If you want the browser to cache all the images what you could do is feed the location of the images into the applet, with a parameter for instance, then create a thread that iterates over the images in the directory and loads them into a hashtable of some kind. So the rendering would be faster. Or put them into a .jar/.zip, would be faster. You don't have to wait for all the images to load to display the first one.
Unless you are manually coding the images in your code you can be fairly certain that the browser is not going to. Perhaps with advanced browsers like Opera, but even then, no.
See ya
Michael

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Cached Image Applet problem

I've created a SSCE below but I can't seem to find the information I need to
format the code correctly, and I've already wasted a half hour trying to find the link to the info.
I found some mentions of links to the info, but when I followed them they were no longer there.
I would think the FAQ would have something about this but it doesn't appear to....
Can someone please point me to how to get the code formatted correctly?
This problem is only with Java 1.6, it works fine with 1.4, 1.5
In any case my problem is with cached images. It would appear that no matter what I do, I can not
get ImageIO.read() to give me an updated image. I use the same file name and change the file in the
use of my GUI.
To use this code you will have to have an image called gdata.jpg in your "codebase" directory. What
I do is bring up the applet, then change the image file in my "codebase" directory and then click on the button.
You'll see commented code in the actionPerformed which loads a image called gdata1.jpg, if this code is there, the new image
is displayed. The ImageIO.setUseCache(false) appears to do nothing but maybe I'm using it incorrectly.
Help please....
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.net.*;
import javax.imageio.*;
import javax.swing.*;
import javax.swing.JApplet.*;
import javax.swing.event.*;
import java.io.*;
import java.io.Serializable;
import javax.swing.border.*;
public class testApplet extends JApplet implements SwingConstants,
ActionListener
JPanel testPanel = new JPanel();
JButton but = new JButton("test");
URL codeBase,graphURL;
Image gImage = null;
Icon iconImage=null;
// init -- Applet Init
public void init()
Container contentpane = getContentPane();
//Get Server IP information.
codeBase = getCodeBase();
try {
graphURL = new URL(codeBase+"gdata.jpg");
} catch(MalformedURLException e) { }
try {
ImageIO.setUseCache(false);
gImage = ImageIO.read(graphURL);
catch(IOException exc) { }
iconImage = new ImageIcon(gImage);
but.setIcon(iconImage);
testPanel.add(but);
but.addActionListener(this);
contentpane.add(testPanel);
// actionPerformed
public void actionPerformed(ActionEvent e)
if ( e.getSource() == but ) {
//If you uncomment out the 3 lines below, changing the name of the image,
// then it works, otherwise I always get the same image.
// try {
// graphURL = new URL(codeBase+"gdata1.jpg");
// } catch(MalformedURLException ex) { }
try {
ImageIO.setUseCache(false);
gImage = ImageIO.read(graphURL);
catch(IOException exc) { }
iconImage = new ImageIcon(gImage);
but.setIcon(iconImage);
but.revalidate();
testPanel.revalidate();
testPanel.repaint();
return;
Edited by: chippr on Sep 13, 2007 10:32 AM

chippr wrote:
That's odd. It looks like I'm using the same version jre plugin under windows...jre-6u2-windows-i586-p.exe.
Which gives me java 1.6_02
So you changed the image and then hit the button and it worked?Yep.
>
hmmmmm, I wonder what the difference is....I'm using firefox under windows, accessing a linux box
running apache....Same here, except I used appletviewer to test the code on the local machine. Let me upload it to my Linux box (running Apache) and I'll let you know what happens.

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thanks,
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Thanks Michael for posting.
Yes... this Safari beta may be the problem, because even after the images have been cached often many of the images on a new page (that have already been cached) reload.
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Hi Raja,
Thanks for your reply, but i guess i was not able to make you understand my scenario. Multiple user ID can belong to a board area. Say, for board area CRM, there are 5 user IDs. From the admin page, news images are uploaded for a board area and they are saved in database table in XSTRING format. In my application, I check which board area any user ID belong to and get the images from the database table and set them one by one to cache as I have depicted in the code and display using the URL from the cache, but it happens every time. what i want now is if any user belonging to same board area logs in, it should not go to the database table to pick the image in XSTRING format and set it to cache one by one again. For that I saved the news link for that board area in another database table. So application picks all the links from database table and display them from cache. But if cache time gets replased, image does not get displayed. I only want to know the process by which I can find out whether a number of images that I uploaded to cache, those are existing or not, i.e. whether caching time has elapsed.
Please let me know if you have any suitable solution for this.
Regards
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thanks
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I've a JSP web application with images.
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--James
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Caching images in a JApplet

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