Java Applet: Caching data in User HDD?

Hi,
I'm trying to write a java applet which requires
approximately 700K of mathematical data everytime it
runs. One way to do this is to download those data off
from server everytime the applet starts up, but it
seems terribly inefficient for me cuz those data do
not change at all.
Is there anyway to work around such issue, for
example, by storing the data into user's hdd? Or is it
possible to pack the mathematical data together with
.class files into a jar file and then somehow access
them in user's side? (dunno how to do so and not sure
if it's possible)
Any help would be greatly appreciated. Thanks.
AaronYou have one answer above.
Create a jar file, put your applet classes in it, and then put the data files in the jar with the application. Theres no restriction as to the types of file you can put in a jar, and Jars are essentially zip files, so no point in zipping the data first.
As to storing stuff locally on the client, that's unadvisable, and disallowed due to the java security model anyhow. It is possible to override the security manager but, I'm not sure if this is possible with an applet though. It would undoubtedly not be hassle free.
Another thing that could help is jar caching..
http://java.sun.com/products/plugin/1.3/docs/appletcaching.html this would improve the start up time by caching the jar file on the client, between invocations.

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Sharing JVM applet cache among multiple users (crosspost)

Does anyone have experience sharing a single JVM applet cache among multiple users?
(This is a crosspost of http://forum.java.sun.com/thread.jspa?threadID=5157018. I know crossposting is frowned on, but it went a week without replies in the plug-in forum.)
Our browser plugin clients run in a Citrix environment where Windows Terminal Services servers host the client sessions for multiple users and the users only have a thin client hardware device at their desks. We've discovered that as a consequence of optimizing certain aspects of the Citrix environment a user's JVM cache is remote to the server hosting his/her browser session, and that the remote caching is a performance bottleneck.
Turning applet caching off improves performance considerably, but we'd like to get the cache directed locally to the server hosting the browser session and turn caching back on. But since hundreds of users times tens of servers in the "Citrix farm" adds up to a lot of cache disk space, we're wondering about users sharing a JVM cache. This already happens when one runs multiple browser/plugin sessions locally on a regular workstation. But what about fifty users' separate plugins sharing a single applet cache? It appears from file timestamps that jars'/classes' idx files in a cache are updated when a file is loaded from the cache. What if multiple browser plugins were trying to do this concurrently? Is there a risk of locking, or a data integrity exposure? Or are those idx updates insignificant since they don't affect the last modified date or the sticky cache version number? (Most apps use a 1_5_0_2 JRE, but some apps require a 1.4 plugin.)
Thanks,
Brian

This sounds very similar to a problem that's occuring for us at the moment. Did you ever find some solution to this problem?
Regards,
Jon.

Sharing JVM applet cache among multiple users

Our browser plugin clients run in a Citrix environment where Windows Terminal Services servers host the client sessions for multiple users and the users only have a thin client hardware device at their desks. We've discovered that as a consequence of optimizing certain aspects of the Citrix environment a user's JVM cache is remote to the server hosting his/her browser session, and that the remote caching is a performance bottleneck.
Turning applet caching off improves performance considerably, but we'd like to get the cache directed locally to the server hosting the browser session and turn caching back on. But since hundreds of users times tens of servers in the "Citrix farm" adds up to a lot of cache disk space, we're wondering about users sharing a JVM cache. This already happens when one runs multiple browser/plugin sessions locally on a regular workstation. But what about fifty users' separate plugins sharing a single applet cache? It appears from file timestamps that jars'/classes' idx files in a cache are updated when a file is loaded from the cache. What if multiple browser plugins were trying to do this concurrently? Is there a risk of locking, or a data integrity exposure? Or are those idx updates insignificant since they don't affect the last modified date or the sticky cache version number? (Most apps use a 1_5_0_2 JRE, but some apps require a 1.4 plugin.)
Thanks,
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This sounds very similar to a problem that's occuring for us at the moment. Did you ever find some solution to this problem?
Regards,
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How to sign java applet policy to end user?

i have putted my applet class on server, i want all end users can access it on server, how to sign the java.policy to there JRE?
can anyone help me?

I found this some where else. It shows how to sign an applet.
START OF DOC
How To Sign a Java Applet
The purpose of this document is to document the steps required to sign and use an
applet using a self-signed cert or CA authorized in the JDK 1.3 plugin.
The original 9 steps of this process were posted by user irene67 on suns message forum:
http://forums.java.sun.com/thread.jsp?forum=63&thread=132769
-----begin irene67's original message -----
These steps describe the creation of a self-signed applet. This is useful for testing purposes. For use of public reachable applets, there will be needed a "real" certificate issued by an authority like VeriSign or Thawte. (See step 10 - no user will import and trust a self-signed applet from an unkown developer).
The applet needs to run in the plugin, as only the plugin is platform- and browser-independent. And without this indepence, it makes no sense to use java...
1. Create your code for the applet as usual.
It is not necessary to set any permissions or use security managers in
the code.
2. Install JDK 1.3
Path for use of the following commands: [jdk 1.3 path]\bin\
(commands are keytool, jar, jarsigner)
Password for the keystore is any password. Only Sun knows why...
perhaps ;-)
3. Generate key: keytool -genkey -keyalg rsa -alias tstkey
Enter keystore password: *******
What is your first and last name?
[Unknown]: Your Name
What is the name of your organizational unit?
[Unknown]: YourUnit
What is the name of your organization?
[Unknown]: YourOrg
What is the name of your City or Locality?
[Unknown]: YourCity
What is the name of your State or Province?
[Unknown]: YS
What is the two-letter country code for this unit?
[Unknown]: US
Is CN=Your Name, OU=YourUnit, O=YourOrg, L=YourCity, ST=YS, C=US
correct?
[no]: yes
(wait...)
Enter key password for tstkey
(RETURN if same as keystore password):
(press [enter])
4. Export key: keytool -export -alias tstkey -file tstcert.crt
Enter keystore password: *******
Certificate stored in file tstcert.crt
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Add all classes used in your project by typing the classnames in the
same line.
added manifest
adding: tst.class(in = 849) (out= 536)(deflated 36%)
6. Verify JAR: jar tvf tst.jar
Thu Jul 27 12:58:28 GMT+02:00 2000 META-INF/
68 Thu Jul 27 12:58:28 GMT+02:00 2000 META-INF/MANIFEST.MF
849 Thu Jul 27 12:49:04 GMT+02:00 2000 tst.class
7. Sign JAR: jarsigner tst.jar tstkey
Enter Passphrase for keystore: *******
8. Verifiy Signing: jarsigner -verify -verbose -certs tst.jar
130 Thu Jul 27 13:04:12 GMT+02:00 2000 META-INF/MANIFEST.MF
183 Thu Jul 27 13:04:12 GMT+02:00 2000 META-INF/TSTKEY.SF
920 Thu Jul 27 13:04:12 GMT+02:00 2000 META-INF/TSTKEY.RSA
Thu Jul 27 12:58:28 GMT+02:00 2000 META-INF/
smk 849 Thu Jul 27 12:49:04 GMT+02:00 2000 tst.class
X.509, CN=Your Name, OU=YourUnit, O=YourOrg, L=YourCity, ST=YS, C=US
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s = signature was verified
m = entry is listed in manifest
k = at least one certificate was found in keystore
i = at least one certificate was found in identity scope
jar verified.
9. Create HTML-File for use of the Applet by the Sun Plugin 1.3
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10. (Omitted See Below)
-----end irene67's original message -----
To make the plug-in work for any browser you have two options with the JDK 1.3 plugin.
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When the reponse comes back, import it into the keystore overwriting the original cert for the generated key.
To export request:
keytool -certreg -alias tstkey -file tstcert.req
To import response:
keytool -import -trustcacerts -alias tstkey -file careply.crt
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2) For development or otherwise, you may want to just use your self-signed certificate.
In that case, the JDK 1.3 plugin will recognize all certs that have a root cert located in the JDK 1.3 cacerts keystore.
This means you can import your test certificate into this keystore and have the plugin recognize your jars when you sign them.
To import self-signed certificate into the cacerts keystore, change directory to where the JDK plugin key store is located.
For JDK 1.3.0_02: C:\Program Files\JavaSoft\JRE\1.3.0_02\lib\security
For JDK 1.3.1: C:\Program Files\JavaSoft\JRE\1.3.1\lib\security
Import your self-signed cert into the cacerts keystore:
keytool -import -keystore cacerts -storepass changeit -file tstcert.crt
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The first time any keystore is accessed (including the default) it will be created and secured with the first password given by the user. There is no way to figure out the password if you forget it, but you can delete the default file and recreate it if necessary. For most operations, using the -keystore command is safer to keep from cluttering or messing up your default keystore.

Java applet cache parameter

I'm sorry if that what I'm looking for is described elsewhere. I couldn't find it. I seem to have a bug with the latest Apple's java implementation (1.5) downloaded with the latest Software Update.
I have to switch off applet caching for a certain applet and tried to do this via the Java preference app. It seems that it doesn't work using the offered checkbox. Because everytime when I check it and leave the dialog and turn back it's still checked. I tried it with the deployment properties file but had no luck not knowing (finding) the correct parameter to set false.
As setting the cache size to zero didn't resolve the problem finally I tried to set the cache path to "/dev/zero" what for sure is the worst solution but it works out. Caching is disabled (This way I discovered that trying to write the cache path in the box in the preference pane you can write it only in reverse manner! llun/ved/ No, it's not a joke)
Anyone could tell me the right parameter for the deployment properties file that I can correct this situation?
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Powerbook Mac OS X (10.4.6)

Unfortunately, this did not resolve the issue. I have been doing a bit more looking and it appears I'm getting a null resource error on reload/refresh:
public abstract class SimpleWindow extends JInternalFram
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public class FancyWindow extends SimpleWindow
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}During startup, it tries to create a new FancyWindow, which calls initComponents(). Inside initComponents is a call to create a JEditorPane.
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My Upgrading Java Applets Cache won't finish

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Hi
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Try [URLConnection.setUseCaches(false)|http://java.sun.com/javase/6/docs/api/java/net/URLConnection.html#setUseCaches(boolean)].

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Can I get help from you?
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Delete user applet cache....(Question) ?

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Hi Romi,
You wrote:
I am looking for any idea or suggestion that how i can delete user's applet cacheYou don't have control over the user's browser, but you can specify the cache version of each jar file in your applet. When you have a new release, you can specify a newer version. If the browser/plug-in follows the version convention, it will download the new jar file and not use the older cached file.
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Was this what you were looking for?
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Hi,
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Thanks

Hi,
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http://java.sun.com/products/plugin/autodl/jinstall-1_4-windows-i586.cab#Version=1,4,0,0
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1. Will these URL's in the html automatically download, or tell the user about the java installations he needs?
2. Is it the Java-Plugin or the Java Virtual Machine users have to download to view java programs?
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1. Will these URL's in the html automatically
download, or tell the user about the java
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�Caleb�

That doesn't help. Had you read my post more carefully you would have better understood what I wanted. In any case, I have already figured out how to automatically forward the non-Java users to the main page. The only thing I worry about now is about the people who's computers crash whenever they try to run a Java applet.
�Caleb�

Updated to FF20.0 Windows 8 64bit up to date Now I have 4mb ea Caches in C:|users\lee\AppData\Local\mozilla\firefox\profiles\tfw6yc7z.default\CACHE_1_

updated to FF20.0 Windows 8 64bit up to date
Now I have 4mb ea Caches in
C:|users\lee\AppData\Local\mozilla\firefox\profiles\tfw6yc7z.default\CACHE_1_
C:|users\lee\AppData\Local\mozilla\firefox\profiles\tfw6yc7z.default\CACHE_2_
C:|users\lee\AppData\Local\mozilla\firefox\profiles\tfw6yc7z.default\CACHE_3_
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and what they are for?
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That looks normal to me. What version did you have before? The layout of the Firefox cache folder changed some time ago so that more files could be accommodated (i.e., to keep performance acceptable because Windows slows down with huge numbers of files in a single directory).
''Edit: Screen shot of file sizes for comparison:''

Java Applet: Caching data in User HDD?

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