Preventing Classloader Cache

As in Subject, how can I prevent class caching? I'm pooling a server, generating a sequence that's naturally dynamic
and need to be overwrited every time. Manually pressing "x" in Java Console, makes everything works fine, but I need something
to permanently disable that. Thanks.

I'm assuming that you mean that you want to cause the classes to reload? Well you can't do that. You have to extend the Classloader and use that classloader to load any class that you want to be able to 'forget'. Sorry.

Similar Messages

Empty classloader cache?

On older MacOS versions, if I needed to empty the classloader cache, I would go the the Java settings and turn on Use Java console. Then, when I loaded an applet, the Java console would pop right up in a new window next to my browser. But this doesn't appear to happen in MacOS 10.4.11. I've tried Safari, Netscape, and Firefox. So, how do I empty the classloader cache if I can't open the Java console? I can see the Java log inside the Console program, but it's just a log -- there's no functionality there.

On older MacOS versions, if I needed to empty the classloader cache, I would go the the Java settings and turn on Use Java console. Then, when I loaded an applet, the Java console would pop right up in a new window next to my browser. But this doesn't appear to happen in MacOS 10.4.11. I've tried Safari, Netscape, and Firefox. So, how do I empty the classloader cache if I can't open the Java console? I can see the Java log inside the Console program, but it's just a log -- there's no functionality there.

How to prevent IE Caching ???

Hi AIl,
I am using dhtmlX tree , to display tree in first jsp and loading the tree using xml file, but when i go to second jsp and come back to first one, i have some changes in the xml file and thus creating new xml file and string on disk to load the new xml again to form the tree in first jsp, but the problem is, due to the IE caching its taking the old xml file from Temporary Internet files folder and thus changes will not reflect... question is how can I prevent this caching of xml file in that folder ......
I tried this but not working
<%
response.setHeader("Cache-Control","no-cache");
response.setHeader("Pragma","no-cache");
response.setDateHeader ("Expires", -1);
%>
<HTML>
<HEAD>
</HEAD>
<BODY>
my page body
</BODY>
<HEAD>
<META HTTP-EQUIV="PRAGMA" CONTENT="NO-CACHE">
<META HTTP-EQUIV="Expires" CONTENT="-1">
</HEAD>
</HTML>
Many thanks in advance !!!

prashant-kadam wrote:
I am using dhtmlX tree , to display tree in first jsp and loading the tree using xml file, but when i go to second jsp and come back to first one, i have some changes in the xml file and thus creating new xml file and string on disk to load the new xml again to form the tree in first jsp, but the problem is, due to the IE caching its taking the old xml file from Temporary Internet files folder and thus changes will not reflect... question is how can I prevent this caching of xml file in that folder ......So the JSP page should load the XML itself and not the webbrowser? How have you confirmed that the problem is with IE? Have you tried another webbrowsers? Have you tried restarting the appserver after XML change and before using IE?
response.setHeader("Cache-Control","no-cache");
response.setHeader("Pragma","no-cache");
response.setDateHeader ("Expires", -1);Looking good.
<HTML>
<HEAD>
</HEAD>
<BODY>
</BODY>
<HEAD>
<META HTTP-EQUIV="PRAGMA" CONTENT="NO-CACHE">
<META HTTP-EQUIV="Expires" CONTENT="-1">
</HEAD>
</HTML>Shouting in HTML is not needed, it's soo 1990s.

Clear the classloader cache

Hi all.
I am trying to clear the classloader cache of the jvm from out my applet.
(Basicaly like typing x on the java console when a applet runs, but automaticallt)
Can this be done ? And if , how ?
Thanks.
globe_sa

I don't think so, you'll have to write your own classloader.

Disabling classloader cache

Hi
I am trying to disable the classloader cache for an applet. I have tried various approaches recommended (both here and elsewhere). I have tried adding a classloader_cache="false" to the applet tag, e.g.:
<applet... classloader_cache="false">
</applet>as recommended here: http://java.sun.com/javase/6/docs/technotes/guides/jweb/applet/best_practices.html
I have also tried adding a parameter, e.g.:
<applet...>
<param name="classloader_cache" value="false">
</applet>as recommended here: http://java.sun.com/javase/6/docs/technotes/guides/jweb/applet/applet_deployment.html#CLASSLOADER_CACHE
Neither of these two methods seem to be succesful. I have tried in firefox 3.0.0, 3.0.11 and various IE browsers.
I can successfully clear the classloader cache via the java console, but this does not help our end users much. Does anyone know how to automatically disable the classloader cache?

If you changing the security properties and restart your application then you will disable caching in InetAddress. On Solaris 8 you may may also wish to shutdown nscd or else changing /etc/nscd.conf with appropriate ttl values for the hosts cache.
As regards where the InetAddress resides - in the Sun implementation it's maintained by an internal HashMap.

Classloader caching in signed applet is very slow and weird

I have a signed applet running in the 1.4.1_01 plugin environment, and
I'm getting the following kinds of messages when I use debug mode 5 in the console:
Connecting http:[myserver]/someclass.class with no proxy
Connecting http:[myserver]/someclass.class with cookie "JSESSIONID=..."
Sometimes, the classloader will say:
WARNING: Unable to cache someclass.class
Moreover, some classes will be repeated two or three times, as if the classloader is trying to get the same class two or three times.
Some of these classes are even in the java.lang package!!
The thing is, I'm actually trying to get the applet to use webservices, so I've signed the Apache Axis jar files (about 8 or so) and included them in the "cache_archive" parameter. The classes giving problems are from these archives, not from my main applet jar.
The applet will eventually work, but the first time takes a LONG time to initialize because the classloader is trying to verify all the classes (i think). Subsequent runnings of the applet within the same browser will be much faster, but the same thing will happen if I start a new browser instance.
My questions are:
1) Why is the classloader trying to load from my http server rather than from the local jars? (they seem to be statically cached, I checked the plugin control panel)
2) Why is the classloader reloading the same classes multiple times?
3) Is the classloader verifying the signatures for each class, because it's taking a long time due to very many classes (100's).
I can't seem to find ANY documentation for this at Sun or Google.
Please help if you can!
Andrew

I've got the same problem with applet using SOAP based on jwsdp.
But classloader only try to get classes from server that are used in SOAP calls.
The only workaround I found is to move this classes to root package, but still there are problems with
Connecting http://<host>/int.class with no proxy
Connecting http://<host>/int.class with no proxy
WARNING: Unable to cache http://<host>/int.class
requests.
Maybe this is a bug of Sun SOAP implementation?

Classloader caching

I am using classloader.getresourceasstream() to read some files. However, for some reason they seem to be cached. So I am suspecting the classloader of caching this data. I know it caches the class files but does it cache the loaded resources too? And if so, is there any way to get past this caching? I want to reload them every time..
Or is there some other easy way to read data from the classpath?

To answer myself, I had to use
classloader.getResource()
and on the URL i get
url.getInputStream()
this is not cached as classloader.getResourceAsStream() is
thank you,

API access to Java Plug-In "x: clear classloader cache" in Java Console

I am using some third-party tools in a Java application I am developing.
I am encountering an error that can be worked around manually by issuing the subject command at the appropriate time. Is there API access to this functionality, so that I can programatically invoke the workaround?
Thanks in advance for your time and consideration.

Well, I finally came to a solution that is acceptable at least to me, if not ideal. I've started using the BouncyCastle lightweight API. This makes my code somewhat more complicated, and I had to bundle up all the BouncyCastle classes that I'm using into a jar file, and download that to my applet along with my client jar file (after signing the jar files). Using this Lightweight API bypasses the Cipher.getInstance() method all together, and is a little harder to use, but at least everything is working consistently now.
I still believe this to be a bug either in the ClassLoader or the Cipher.getInstance() method. I intend to try to write a test applet that reproduces the error in a more simple way and if I can pull that off, I'll submit a bug report to Sun.
Thanks to all who responded!!
Steve

Prevent servlet caching

I am having problem with servlet caching. My Servlet keeps displaying
previously cached image instead of an updated image. I tried out the
following workarounds and was not successful.
1. Set the following Response headers
res.setDateHeader("Expires", 0);
res.setHeader("Cache-Control", "no-store, no-cache, must-revalidate,
post-
check=0, pre-check=0");
res.setHeader("Pragma", "no-cache");
2. Set HTML META TAG:
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
<META HTTP-EQUIV="Expires" CONTENT="0">
Has anyone experienced a similar issue and can you share your
worarounds. I even tried setting DateHeader as follows but no luck.
res.setDateHeader("expires", System.currentTimeMillis()).
thanks in advace

And is this servlet actually sending the image itself, or it is sending some HTML that contains a link to the image? If it's the latter, then no amount of saying not to cache the HTML will have any effect on whether browsers cache the linked image.
Actually now that I read your post more carefully, I see that you are sending HTML which presumably has an <img> tag referring to the image. The browser will download that image as a separate transaction. But if you change the date on the image file to something later, the browser should stop caching it.

Urgent Help - Preventing Cache in Flex 3

Hi all,
Am new to this forum and i have a query which needs to be fixed urgently. Actually Flex 1.5 supports <cache> configuration variable in flex-config.xml which can be used to prevent client-side caching. But I suppose Flex 3 doesn't support the <cache> configuration variable, as am getting compilation error as 'unknown configuration variable compiler.cache' . Could any one please help me out with this? And also please suggest any ideas for preventing client-side caching. Also is there any other relative terms to <cache> configuration variable in Flex 3?
I had referred the below url regarding the <cache> variable in Flex 1.5 , http://livedocs.adobe.com/flex/201/html/wwhelp/wwhimpl/common/html/wwhelp.htm?co ntext=LiveDocs_Book_Parts&file=performance_118_13.html
Thanks in Advance.

Thanks a lot for the response.
Actually i heard that using <cache> seems to be easy, where in we could specify even the content-size to get cached (if we require) and also it just requires us to add something like <cache-mxml>false</cache-mxml> which will prevent the caching.
And i have already tried appending the random number to the url. In the link provided by you, what does the swfObject refer to. I mean i couldn't find any reference to the object.
Am trying like this,
In index.template.html
AC_FL_RunContent(
"src", "${swf}?url="+Math.random(),"width", "${width}","height", "${height}","align", "middle",.........)
Please guide me thru'.
Thanks again

Preventing cache in all browsers.

Hi all,
To prevent browser cache I have added the following code
<meta http-equiv="Cache-Control" content="no-cache">
<meta http-equiv="Expires" content="0">
<meta http-equiv="max-age" content="0">
in one of my jsp(sample1.jsp). This JSP is included in all the other JSPs.(sample2.jsp,sample3.jsp)
The sample2.jsp have a link to sample3.jsp. The sample2.jsp is reloaded everytime I click the tree option.This tree node points to sample2.jsp.
The sample3.jsp is not loaded eveytime I click the link.(sample3.jsp?name=David- the value link in sample2.jsp)
Can anybody suggest me to solve this?

Here is one set of magic spells I picked up somewhere:
        response.addDateHeader("Expires", 791589600000L); // Wed Feb 01 00:00:00 EET 1995
        response.addHeader("Cache-Control", "no-store, no-cache, must-revalidate, post-check=0, pre-check=0");
        response.addHeader("Pragma", "no-cache");Those should cover reasonable browsers, as well as most versions of Internyet Explorer. I don't know if those work with <meta http-equiv=...>, you could try.

Prevent caching of JARs

Dear Friends,
somtime I actualize my JAR-Files.
And I don't want that the user has to delete his java-Cache, etc. - That's not acceptable for that group of users.
How can I prevent caching of my JAR-File?
The JAR is only 70 kb big and wouldn't disturb.
Well, actually I use a meta pragma nocache - but does that really help?
Is there a secure way to prevent the caching to the harddrive (after a browser-session) ?
Thank you!
With best regards
MfG
Inno

Dear Friends,
somtime I actualize my JAR-Files.What is that trying to say ?
Does your jar have feelings and dreams - is it trying to better itself ? (Sorry I couldn't help, just did a psych test ;-P )
In all seriousness it would help if you explain what type of program this is, what you mean by caching jars, and why it is an issue.
And I don't want that the user has to delete his
java-Cache, etc. - That's not acceptable for that
group of users.
How can I prevent caching of my JAR-File?
The JAR is only 70 kb big and wouldn't disturb.
Well, actually I use a meta pragma nocache - but does
that really help?
Is there a secure way to prevent the caching to the
harddrive (after a browser-session) ?
Thank you!
With best regards
MfG
Inno

Swf streaming or preventing caching

Folks
I have swf files generated from Captivate - I want to stream
these to prevent browser caching and conceal original file location
Can anyone point me to sample files or notes on how to do
this using Flash media server?
I have managed to glean that it might be posible - swf file
on web site connects to asc file on Flash media server which then
gets the actual swf from location on web server and serves it via
Flash media server to the client - but I need to see an example
Looking for either free or fee source
Regards
Steven

FMS does not serve .swf files... only flv and mp3. If you
want to conceal the server path to the .swf, I suggest you use an
application server (like ASP or PHP) to act as a proxy between the
user and the .swf
For the caching issue, you can give the .swf nocache headers
(again, you'd need an application server for that), but honestly,
there is no foolproof way of protecting .swf content or preventing
people from downloading it for themselves. The best you can do is
create a lot of hoops for people to jump through in order to get
there.

Null Pointer and cache problem

Simple program...reads 4 images from html and prints them on the page. That all works, but when observing the java console, a "Null Pointer Exception" error pops up after a while. I believe it has something to do with the cache. Is there any way you can see to avoid this error showing in the java console? What in tarnation could be causing this?
Here is the snip from the consol:
Java(TM) Plug-in: Version 1.4.1_02
Using JRE version 1.4.1_02 Java HotSpot(TM) Client VM
User home directory = C:\WINDOWS
Proxy Configuration: Browser Proxy Configuration
c: clear console window
f: finalize objects on finalization queue
g: garbage collect
h: display this help message
l: dump classloader list
m: print memory usage
o: trigger logging
p: reload proxy configuration
q: hide console
r: reload policy configuration
s: dump system properties
t: dump thread list
v: dump thread stack
x: clear classloader cache
0-5: set trace level to <n>
Trace level set to 5: basic, net, security, ext, liveconnect ... completed.
Logging set to : true ... completed.
Cache size is: 52022779 bytes, cleanup is necessary
Apr 29, 2005 4:40:02 PM sun.plugin.usability.PluginLogger log
INFO: Cache size is: 52022779 bytes, cleanup is necessary
java.lang.NullPointerException
     at sun.plugin.cache.CacheFile.getFileType(CacheFile.java:81)
     at sun.plugin.cache.CacheFile.before(CacheFile.java:127)
     at sun.plugin.cache.CleanupThread$1.compare(CleanupThread.java:204)
     at java.util.Arrays.mergeSort(Arrays.java:1237)
     at java.util.Arrays.mergeSort(Arrays.java:1244)
     at java.util.Arrays.mergeSort(Arrays.java:1245)
     at java.util.Arrays.mergeSort(Arrays.java:1244)
     at java.util.Arrays.mergeSort(Arrays.java:1245)
     at java.util.Arrays.mergeSort(Arrays.java:1244)
     at java.util.Arrays.mergeSort(Arrays.java:1244)
     at java.util.Arrays.sort(Arrays.java:1185)
     at sun.plugin.cache.CleanupThread.getFilesInCache(CleanupThread.java:200)
     at sun.plugin.cache.CleanupThread.cleanCache(CleanupThread.java:122)
     at sun.plugin.cache.CleanupThread.run(CleanupThread.java:93)
Here is a snip of the html page:
<applet code="jewelry3custom.class" align="baseline"
width="750" height="300" >
<param name="image1"      value="web-heart-musician-4.jpg">
<param name="image2"      value="web-circle-musician-4.jpg">
<param name="image3"      value="web-oval-musician-4.jpg">
<param name="image4"      value="web-rectangle-musician-4.jpg">
<param name="BackGround" value="FFFFFF">
<param name="Steps"      value="277">
<param name="Speed"      value="16">
</applet>Here is the java program:
*          Created on Apr 25, 2005 7:16:27 AM
import java.awt.*;
import java.awt.image.*;
import java.util.*;
import java.applet.*;
import java.awt.event.*;
import java.awt.event.MouseEvent;
public class jewelry3custom extends Applet implements MouseListener
     Image imag1, imag2, imag3, imag4;
public void init()
          imag1 = getImage(getDocumentBase(), getParameter("image1"));
          imag2 = getImage(getDocumentBase(), getParameter("image2"));
          imag3 = getImage(getDocumentBase(), getParameter("image3"));
          imag4 = getImage(getDocumentBase(), getParameter("image4"));
public void paint(Graphics g)
     g.drawImage(imag1,10,10,100,100,this);
     g.drawImage(imag2,120,10,100,100,this);
     g.drawImage(imag3,230,10,100,100,this);
     g.drawImage(imag4,340,10,100,100,this);
public void mouseClicked(MouseEvent event){
public void mousePressed(MouseEvent event){
public void mouseReleased(MouseEvent event){
public void mouseEntered(MouseEvent event){
public void mouseExited(MouseEvent event){
}

Those database defaults are only applied when you use an INSERT statement that specifies a list of columns excluding the ones with defaults. Presumably your persistence code always sets all columns when it does an INSERT, so the defaults won't apply. You'll have to find the way to set the defaults in the persistence layer, not in the database.

Caching problem of javascript with servlet

Hi guys
There is a problem of caching with the our project. This project contains two servlets first is getAdServlet and second is richMediaServlet. getadservlet is called thru <script src=""> following is the code:
<script LANGUAGE="JAVASCRIPT" src="http://192.168.1.6:8080/advert_java/servlet/GetAdServlet?region=1&zone=1&type=nossi&cachevar=yes">
</script>
getadservlet returns the javascript statments. These javascript statments are able to create an <iframe>. Now cotents of the iframe are supplied by the second servlet ie richMediaServlet. This servlet is called like
iframeURL = fullHttpDir+"/servlet/RichMediaServlet?";
iframeURL += "bannerCode="+ RNBanner;
iframeURL += "&cachebust="+ cachebust + refresh+"&getAd=y";
iframeURL += "&hheight="+hheight+"&wwidth="+wwidth;
out.println("document.write(\"<iframe src='" + iframeURL + "' height=" + hheight +" width="+ wwidth + " SCROLLING=no FRAMEBORDER=0 MARGINWIDTH=2 MARGINHEIGHT=2 onfocus='window.focus(); return iframeFocus()'>\");");
out.println("document.write(\"</iframe>\");");
This richmediaServlet returns HTML into <iframe>. when richmediaservlet is called, a parameter 'bannerCode' is passed. then richmediaServlet fatches the banner from the database and displays the banner into the <iframe>.
Now the problem is when i run the html file containing the script tag mentioned above, and supply different bannerCodes from getAdServlet to richMediaServlet then first banner is cached and displayed every time.
i have also used the following code to prevent the caching of both the setvlets
     long currentTime = System.currentTimeMillis();
     response.setHeader("Cache-Control", "no-cache, must-revalidate");
     response.setHeader("Pragma", "no-cache");
     response.setDateHeader("Last-modified", currentTime);
     response.setHeader("Expires", "Sat, 6 May 1995 12:00:00 GMT");
and following in the iframe's head tag before the iframe tag in the getAdServlet.
out.println("document.write('<head>');");
out.println("document.write('<meta http-equiv=\"Cache-Control\" content=\"no-cache,must-revalidate\">');");
out.println("document.write('<meta http-equiv=\"Pragma\" content=\"no-cache\">');");
out.println("document.write('<meta http-equiv=\"Last-modified\" content=\""+ currentTime + "\">');");
out.println("document.write('<meta http-equiv=\"expires\" content=\"Sat, 6 May 1995 12:00:00 GMT\">');");
out.println("document.write('</head>');");
this problem does not arises when i call the getAdServlet from a testServlet and run the testServlet thru get request.
pl tell me what's wrong i m doing.

First, post your code in tags if you want people to read your code...

Preventing Classloader Cache

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