Multiple repeat downloads of applet jar file

We have an applet that is downloaded from a Weblogic server. The applet is packaged as a jar file. Some of the testers have been complaining that the applet is extremely slow to start up.
The applet start-up involves three phases. In a first phase, it fetches data from the server. This phase seems to execute in pretty much constant time. During the second and third phases, it constructs a UI using Swing objects. The UI includes some JPEG files, which are extracted from the applet's own jar file.
Testers report that the slow part of start-up is actually the UI setup. This should theoretically not be network-bound at all. But packet tracing reveals that during this phase, there's a large amount of network traffic going on. It turns out that there are multiple GET requests for the applet jar file being issued. Typically, 29 requests are issued in all; just for reference, the applet is required to extract 28 images from its jar file, so it looks as if the additional requests correspond to image requests.
One further detail: this does not occur where there is a fast connection to the server. In these cases, the applet is downloaded once. It looks as if the problem only occurs on slower network connections, and the speculation here is that the applet jar is somehow being downloaded only partially, so that requests for images somehow trigger a re-request of the jar file.
Has anyone seen anything similar and, more to the point, is there a fix or workaround?
Technical details: Internet Explorer 5.5 or 6.0, JRE version 1.4.2_01 Java HotSpot(TM) Client VM (on the client), WebLogic 8.1 (on the server)
Thanks in advance for any help.

Ok.
I have been trying hard and found the solution. One of the ablove posting says that it works under java 1.4.1 plug-in. That's infact absolutely true. It also says that how to run client using JRE 1.4.2 or higher. That can be solved two. This is definitely a bug with the 1.4.2 plug-in.
Follow this procedure that will solve the mystry.
----------------------start ---------------------------------
Problem
Download of applet is very slow
Why?
This was happening because of the repeated download of the applet jars by the applet plug in controller. It is quite clear that the Java 1.4.2 plug in controller has a bug that causes the plug in to download same jar files multiple times irrespective of Jar cache in the client side (configurable from client side using the Java plug in control panel) is enabled or disabled. Therefore, we have moved from 1.4.2 plug in to 1.4.1 (controlled from our client (JSP) code) that works fine.
What the client (applet client) should do?
You must do the following in the client side in order to avoid the long download time for applet when running from a browser. We have also found that the browser actually do not matter in slow applet downloads. It is only the plug in that does control the applet download.
Irrespective of what JVM you have already installed (or not yet installed) please do the following:
1. Download the JRE 1.4.2 from http://java.sun.com/products/archive/index.html
-At the time of its installation if it shows that the "JRE is already installed do you uninstall it?" Go ahead and uninstall the JRE 1.4.2. After the un-installation again install the JRE 1.4.2
-If it does not have the JRE 1.4.2 already installed, then you will see any warning window and you will be able to install the 1.4.2 JRE successfully.
2. Now, go to the same link and install JRE 1.4.1.
-If this JRE already installed, uninstall first like the step 1 above. then reinstall it.
3. Now, after successful installation of the JRE 1.4.1, open the Plug-In control panel.
-You will find the list of control panel(s) in the Start->Control Panel window. Use the control panel that shows the version number 1.4.1. If no version number shown then use the one that do not show any version number at its end.
4. Do the following on the Plug-In control panel.
-Verify if this is the 1.4.1 plug in control panel? Go to the "About" tab to see if it shows 1.4.1.
If it does not show the 1.4.1 (or 1.4.1_x) then plug in was not installed correctly. Reinstall the 1.4.1 JRE following the step in no-2
-Go to "Basic" tab and select "Show console" radio button.
-Go to "Advanced" tab and from the drop down select "JRE ...1.4.2" from the "Java Runtime Environment" drop down box.
-Go to "Browser" tab and select all that in the "Settings" box applicable for browsers.
-Go to "Cache" select "Enable Caching" if it is not selected currently. Select "Unlimited" from "Size" options.
Now hit "Apply" button at the bottom and close the control panel using the 'X'.
5. Restart your Windows machine.
6. You are ready to run the applet from any of the browser (IE, NS, etc.)
--------------------------end------------------------------

Similar Messages

How to load an applet jar file?

Hello everyone,
I have an applet that uses my own jar file and approximately 6 third party jar files. I set up jar indexing (jar -i) which will download the jar files when they are needed. All seems to work well, but now I want to manually load the jar files which I cannot get working.
When the applet starts, about 1/2 of the jar files are downloaded (because they are needed at startup). I then want to load the additional jar files in the background, after the gui is initialized. I have tried this using the below thread which is executed from within the applet's start method:
// Try to load additional jar files in background by loading a class from each jar file.
Thread loadClass = new Thread() {
public void run() {
    System.out.println("Loading classes...");
    try {
      // Tried loading classes this way, doesn't work.
      getClass().getClassLoader().loadClass("pkg1.Class1");
      getClass().getClassLoader().loadClass("pkg2.Class2");
      getClass().getClassLoader().loadClass("pkg3.Class4");
      getClass().getClassLoader().loadClass("pkg4.Class4");
      /* Loading classes this way doesn't work either.
      Class.forName("pkg1.Class1");
      Class.forName("pkg2.Class2");
      Class.forName("pkg3.Class3");
      Class.forName("pkg4.Class4");
    catch(ClassNotFoundException e) {
      // First attempt to load a class (pkg1.Class1) throws exception.
      System.out.println("Can't find class: " + e.getMessage());
loadClass.start();As you can see from above I am trying to load a class from each of the jar files so that the jar files would load into memory/cache. Unfortunately, it cannot find the classes. These are the errors from the java console:
Loading classes...
Loading: pkg1.Class1
Connecting http://my.server.com/my_dir/pkg1/Class1.class with no proxy
Connecting http://my.server.com/my_dir/pkg1/Class1.class with cookie "JSESSIONID=some_big_long_char_list"
Can't find class: pkg1.Class1
So it appears the jar file is not being downloaded. When I take away the dynamic jar loading (removing the "jar -i" & adding them all to the applet archive list) the thread executes correctly. So I know the class names, etc, are correct. How does one load an applet jar file?
Any help/suggestions are appreciated.

The above error I posted was because I forgot to index the jar files. That is why it couldn't find the jar file. I thought I was getting farther along with my problem, but I apparently just forgot to index the jars. I am now getting the problem that I got yesterday...
The applet freezes/hangs when it hits the thread. The GUI never opens (even though I'm running this thread right after the gui shows). The java console quits responding and the applet just stays the grey screen. I also tried the invoke later that you suggested.
public void start() {
// ...initialize gui...
// Applet freezes and remains grey, also the java console freezes.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
    public void run() {
      System.out.println("Loading classes...");
      try {
        // When I comment out the below forName calls, the thread will still run evidenced through the done print statement.
        Class.forName("pkg1.Class1");
     Class.forName("pkg2.Class2");
     Class.forName("pkg3.Class3");
     Class.forName("pkg4.Class4");
        System.out.println("...Done loading classes");
      catch(Exception e)     {
        System.out.println("Can't find class: " + e.getMessage());
}

Where is the Applet JAR file?

When an Applet (the JAR) is downloaded to the local PC, exactly where (the directory) we can locate the Applet JAR file? Is the file managed by the Internet browser?

This has got to be browser-specific.
You shouldn't write code that depends on this kind of information anyway.

Question about Java Applet Jar file signing.

These questions pertain to Java 6 Standard Edition 1.6.0_22-b04 and later.
I have gone through the Oracle Java Tutorial for generate public and private key information
to sign a jar file, and how to sign the jar itself, all at
[http://java.sun.com/developer/onlineTraining/Programming/JDCBook/signed.html|http://java.sun.com/developer/onlineTraining/Programming/JDCBook/signed.html]
, and seek some clarification on the following related questions:
-In order to "escape" the java applet sandbox that exists around the client's
copy of the applet running in their web browser, ie.
(something forbidden by default), is verification of the signed applet enough, or is a policy file required
to stipulate these details?
-using the policytool policy file generator, what do I need to add under "Principals"
(if anything) when dealing with a Java applet? Are Codebase and SignedBy simply author information?
-If I choose to use a java.security.Permission subclass object set up in equivalent fashion within the Applet,
which class within the Applet jar do I instantiate that object in? Does it need to be mentioned
in the applet's jar Manifest.MF file?
-Is the "keystore database" a java language service/process which runs in
the Server's memory and is simply accessed and started by default
by the client verifier program (appletview/web browser)?
-The public key certificate file (*.cer) is put in the webserver directory holding
the Applet jar file (ie. Apache Tomcat, for example).
-Presumably, the web browser detects the signed jar
and certificate file, and provides the browser pop up menu asking the user
about a new, non recognised certificate (initially).
Is this so?
-With this being the case, can the applet now escape
the sandbox, be it with or without the stipulated
policy permissions?

848439 wrote:
-In order to "escape" the java applet sandbox that exists around the client's
copy of the applet running in their web browser, ie.
(something forbidden by default), is verification of the signed applet enough, or is a policy file required
to stipulate these details?Just sign the applet, the policy file is not necessary.
-Is the "keystore database" a java language service/process which runs in
the Server's memory and is simply accessed and started by default
by the client verifier program (appletview/web browser)?No.
-The public key certificate file (*.cer) is put in the webserver directory holding
the Applet jar file (ie. Apache Tomcat, for example).No. For a signed Jar, all the information is contained inside the Jar.
-Presumably, the web browser detects the signed jar
and certificate file, and provides the browser pop up menu asking the user
about a new, non recognised certificate (initially).
Is this so?No. It is the JVM that determines when to pop the confirmation dialog.
-With this being the case, can the applet now escape
the sandbox, ..Assuming the end-user OK's the trust prompt, yes.
..be it with or without the stipulated
policy permissions?Huh?

My Applet Jar file doesn't work !!

hello ,
I have written this java applet :
import java.awt.*;
import javax.swing.*;
import java.applet.Applet;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.net.URL;
public class test4 extends Applet implements ActionListener{
     private static final long serialVersionUID = 1L;
     private JButton B1 =new JButton("Forward ");
     private JButton B2 =new JButton("Backward");
     private JButton B3 =new JButton("Left");
     private JButton B4 =new JButton("Right");
private JPanel P1 = new JPanel();
private JPanel P2 = new JPanel();
private JPanel P3 = new JPanel();
private JPanel P4 = new JPanel();
private JPanel P5 = new JPanel();
private JPanel P6 = new JPanel();
private JLabel L3 = new JLabel(" ");
private JLabel L4 = new JLabel(" ");
private JLabel L5 = new JLabel(" ");
private JLabel L6 = new JLabel(" ");
private JLabel L7 = new JLabel(" ");
JSplitPane sppSplitPane0 = new JSplitPane( );
     public test4()
          JFrame.setDefaultLookAndFeelDecorated(true);
          sppSplitPane0.setDividerLocation( 250 );
          P3.add(L4);
          P3.add(B1);
          P3.add(L5);
          P5.add(B3);
          P5.add(L3);
          P5.add(B4);
          P4.add(L6);
          P4.add(B2);
P4.add(L7);
          P1.setLayout(new BorderLayout());
          P1.add("North",P3);
          P1.add("Center",P5);
          P1.add("South",P4);
          P2.setLayout(new BorderLayout());
          P2.add("North" , P1);
          B1.addActionListener(this);
          B2.addActionListener(this);
          B3.addActionListener(this);
          B4.addActionListener(this);
          sppSplitPane0.setLeftComponent(P2);
          sppSplitPane0.setRightComponent(P6);
     public void actionPerformed(ActionEvent e) {
          try {
               if (e.getSource() == B4) {
          URL myNewURL = new URL("http://amera/cgi-bin/test.cgi?R");
          System.out.println("URL = " + myNewURL);
          getAppletContext().showDocument(myNewURL,"blank");
               else
                    if (e.getSource() == B3) {
                    URL myNewURL = new URL("http://amera/cgi-bin/test.cgi?L");
                    System.out.println("URL = " + myNewURL);
                    getAppletContext().showDocument(myNewURL,"blank");
                    else
                         if (e.getSource() == B2) {
                         URL myNewURL = new URL("http://amera/cgi-bin/test.cgi?B");
                         System.out.println("URL = " + myNewURL);
                         getAppletContext().showDocument(myNewURL,"blank");
                         else {
                              URL myNewURL = new URL("http://amera/cgi-bin/test.cgi?F");
                              System.out.println("URL = " + myNewURL);
                         getAppletContext().showDocument(myNewURL,"blank");
          } catch (Exception err) {
          System.err.println("Error!\n" + err);
          showStatus("Error, look in Java Console for details!");
     public static void main(String[] args) {
          test t=new test();
          JFrame frame =new JFrame();
          frame.add(t.sppSplitPane0);
          frame.setSize(1100,700);
          frame.setVisible(true);
i made a jar file :
i created a file and named it MANIFEST.MF .i wrote inside it :
Main-Class: test
Then i placed it in a folder with the test.class .I created jar file using command line.
I entered the test.class path and then wrote this command :
jar cvfm myjar.jar MANIFEST.MF *.class
Then the jar file "myjar.jar" is created .
it's executed but this function "public void actionPerformed(ActionEvent e) " won't wrok.
i keep pressing the buttons but nothing is happening !!
please help me .
Edited by: Amera on Dec 27, 2009 2:51 PM

Welcome to the Sun forums.
Subject: My Applet Jar file doesn't work !! .
1) Note that one '!' denotes exclamation, whereas 2 or more often denotes a dweeb.
2) Since you are on your first post, I will point out that applets are an advanced topic, and should not be attempted by newbies.
3) "doesn't work" is very vague. It is likely to produce a reply like "maybe the applet is lazy - try flogging it".
Amera wrote:
..I have written this java applet :When posting code, code snippets, HTML/XML or input/output, please use the code tags. The code tags help retain the formatting and indentation of the sample. To use the code tags, select the sample and click the CODE button.
Also note that the most preferred form of code is an SSCCE *(<- link).* In an SSCCE, your would remove all but one button (if the actionPerformed fails with 6 or 7 buttons, trim it down to fail with just one or two.
i made a jar file :So does the applet work before you make the Jar file? Your post so far suggests the Jar file is the problem.
i created a file and named it MANIFEST.MF .i wrote inside it :
Main-Class: test
Then i placed it in a folder with the test.class .I created jar file using command line.
I entered the test.class path and then wrote this command :
jar cvfm myjar.jar MANIFEST.MF *.class
Then the jar file "myjar.jar" is created .
it's executed but this function "public void actionPerformed(ActionEvent e) " won't wrok.
i keep pressing the buttons but nothing is happening !!So you get 'no output in the console & no effect in the applet'?
What is the URL where I can see your applet failing?
As an aside, since Sun does not guarantee that applet clients will act on the showDocument command, even if it does not work, it would not be a 'bug'.
Edited by: AndrewThompson64 on Dec 28, 2009 11:18 AM

Anybody knows where to download the dco.jar file????

hi,
do u guys know where i can download the dco.jar file ???
(Domino Collaboration Object - Lotus Domino)
It seems that i really cnt find it....
thanks

It's part of the toolkit, it seems. Some more googleing:
http://www-10.lotus.com/ldd/sandbox.nsf/ecc552f1ab6e46e4852568a90055c4cd/898382b7d610f43d88256ad4005899c8?OpenDocument
I wish you would search a little yourself.

Cipher.getInstance closes Applet JAR file.

I am trying to use a Cipher in a signed Applet in java plugin-1.4 under I.E. Once I execute a Cipher.getInstance the applet jar file is closed and I cannot create any new classes that havent been previously loaded from it. The classloader ends up returning an "IlleagleStateException: Zip file closed".
Is this a known bug? Is there a workaround? Perhaps a way to re-open the JAR file.
I have been combing the FAQ's without finding any other refrences to the problem.

I haven't found a solution to the original problem but for someone else that is looking for a workaround for this. I found that if I use two JAR with my Cipher in the second one, I can still load class files out of the first. I.E. <PARAM NAME = java_archive VALUE = "supportClasses.jar,mainApplet.jar"> where mainApplet.jar contains the code that uses the Cipher.

Download and extract jar file from applet

Can any one provide me a solution for my below problem. Thanks in advance for all the suggestions.
I want my applet to download a jar file, extract into users home directory by creating a folder and then set the created folder to java library path.
My applet html file is in "root" directory. The applet is included into applet.jar and placed under "lib" directory which is under "root" directory.
Now i also had another jar file(contains dlls what I packed) under the same lib folder.
The below is the following directory structure in my server.
root ---
     |
     |
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     lib--
     |
     |
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     native.jar - contains dlls which are to be loaded
When a client downloads my applet, it should copy the native.jar and then extract into a new folder under user home directory. Then set this folder to java library path.
Regards
raman kumar

I managed to do it this way, Just remember that you need to sign the jar files for your applet, else it won't work.
package jar.extract;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.jar.JarFile;
import java.util.zip.ZipEntry;
public class JarExtractor {
     // Dll file in the jar
     private static String JAR_FILE = "dll.jar";
     public void extract() {
          try {
               JarFile jf = new JarFile(JAR_FILE);
               // Entry in the jar file rember package and dll file
               ZipEntry ze = new ZipEntry("package/dll_file");
               int length = (int) ze.getSize();
               byte fileContent[] = new byte[length];
               InputStream fin = jf.getInputStream(ze);
               fin.read(fileContent, 0, length);
               // CODE missing.
               // You need to write the input stream (fin) to a new files output stream
               // it is like copying a file !!!
          } catch (IOException e) {
               e.printStackTrace();
}Tom

Display splash screen while downloading applet jar file

I've tried to search the forums, but most results I get are how to display a splash screen while the classes are loading. Unfortunately, the classes do not begin loading until after the jar file has been downloaded. How does one go about showing as splash screen as the jar file containing the classes is downloaded?
Thanks for the help!

"Java 5 provides a capability in this area"- Unfortunately, due to circumstances out of our control we are stuck on java 1.4.x.
"How you do that is your problem."- I'm so glad I can count on the helpful java community. Thanks.
Since it appears that "warnerja" is discusted by my question (mabye had a bad day) and is leaving me out in the cold, does anyone have any ideas on how I can implement her/his suggestion. I can break my jar file into multiple seperate jars and as each one loads I can update a progress bar. Unfortunately, I do not know where to begin with this code wise nor do I know if this is the best solution to this problem. I would think this to be a common problem.
Thanks for your help!

How do I download themes as .JAR files?

Hello. I would like to make a Firefox Theme, using this theme as a base (https://addons.mozilla.org/en-US/firefox/addon/msn-blue/ ) and this guide (http://www.twistermc.com/959/how-to-create-a-firefox-theme/ ). The guide says to download the theme as a .JAR file. How do I do this? The guide says "Download the theme to your computer. To do this, right click and save link as in Firefox." This doesn't work, just wants me to save a HTML file.
Thanks,
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fixed link ~J99

Parts of the answer to the question may depend on the Operating System, or the software already installed and you may then have further questions relating to creating an addon, so you probably would be better going on to the Addons Forum and asking over there
* Forum https://forums.mozilla.org/addons/viewforum.php?f=30
*Instructions https://addons.mozilla.org/en-US/developers/docs/themes

Applet jar file

I have an applet embedded in a jsp as follows
<applet code="MyApplet.class" archive="client.jar" height="1" id="APface" name="APIface" width="1" mayscript="true">
</applet>
Now as mentions MyApplet.class is archived in the client.jar file. I am running the application of websphere. Now whats happeneing is the the jsp is located in <proj>/web Content/html directory. What I have to do is to run the application is to put the jar file in this folder too. What I want to do is to put the jar file in the web-inf/lib folder instead of putting it here. how could I do that?

yes, or in a jar specified in the archive parameter...
Are your classes in a package? I would generally set
up this type of structure:
/mainWebDir/
/mainWebDir/appletWebPage.html (or .jsp)
/mainWebDir/applets/
/mainWebDir/applets/classes/
/mainWebDir/applets/classes/*.class <-- loose
non-packaged classes
/mainWebDir/applets/classes/the/package/dirs/*.class
<-- loose packaged classes
/mainWebDir/applets/lib/*.jar
<applet class="MainClass.class"
codebase="applets/classes"
archive="./applets/lib/a.jar, ./applets/lib/b.jar" >My directory structure is as follows
MyProject/JavaSource contains all the java code
MyProject/webContent/html contains the html files and the jsp's. This is where the jar files were placed originally used by the applet. But what I have done is replaced the jar files with class files now in their respective hierarchy.
MyProject/webContent/WEB-INF/lib contains all the jar files
MyProject/webContent/WEB-INF/classes contains all the compiled code.
SO should I move all the class files used by the applet to the html folder. Please correct me if I am wrong.

Download problem on jar file

i have put a jar file on my web server,
and put following link in my web page
a jar file
i my local machine, this link work.
my IE5.5 ask me do i want to excute it directly....
but when i put it in to web server
the file renamed as "abc.gtz" on download....
why this problem come?? is this cause by the browser or the IIS server ??

can you switch to apache?

Applet -JAR files

hi,
can anybody explain ans for doubt that im posting below
For the applets that includes jar files , for some applet it will work if we place jar files in server and make include in applet tag, but some applet it will wont work, those jar files(or may be class file s also) should also kept in clientside classpath to clean working of applet.
why this behaviour by applet what r the conditions on that we should keep the jar file on client side
please anybody could explain this
thanks in advance

This may be of help
http://java.sun.com/docs/books/tutorial/deployment/applet/html.html

To how unzip trsuted applet jar file

hi to all,
I have created a trusted applet signed jar file.Now now i want to unzip the this jar file..but i am unable to do it......
so please help me
Thanks and Regards

Yes, I thought you would not like that answer. If you want a better answer, ask a better question. Provide useful information like what you have tried, what error messages you are getting, and so on. "I am unable to do it" is not useful information.

Multiple Class-Path: attributes in Jar files

Hello,
I'm packaging a set of jar files for distribution with Class-Path: attributes in them. In the documentation I read and in one of the java trails it said that I could have a manifest file like:
Class-Path: log4j.jar log4j-core.jar
Class-Path: jsse.jar jcert.jar jnet.jar
But this doesn't work. It only works when I do this:
Class-Path: log4j.jar log4j-core.jar jsse.jar jcert.jar jnet.jar
Here is how I'm running the jar:
java -jar server.jar
Is the documentation wrong? Or this is a bug?
thanks
charlie

Certain attributes were only meant to be specified once. Like Main-Class and Class-Path for example. If these were listed two or more times, then the last occurance is the one that gets recognized (basically, each new instance overwrites the previous instance). Some attributes are listed as "per-entry" and are freely duplicated for each entry. For example signed jars could have a number of Name: and xxx-Digest: attributes.
This link is to the manifest spec:
http://java.sun.com/products/jdk/1.2/docs/guide/jar/manifest.html
To answer the original posters question, the doc's are in error. Actually, the error was not in the docs, it was in the tutorial, but none the less its still in error. He could have done this:
Class-Path: log4j.jar log4j-core.jar
jsse.jar jcert.jar jnet.jar
^-- two spaces before the start of jsse.jar
because the docs allow for line continuation (although it's not exactly clear if you read the docs). The docs are also apparently in error regarding the max line length of 72 bytes. I have tested this with over 100 char's on a win32 machine and it works fine for me. The limitation must therefore apply to some other operating system, or it could just be in error.
-Ron

Multiple repeat downloads of applet jar file

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