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.

Similar Messages

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.

Servlet caching ????

I input a name to a servlet and try to print out something with that name.Say , for ex. I enter "Bryan" and the output wud be "Bryan belongs to section C"
when 2 or more users enter names from different machines using the same servlet at the same time..sometimes it happens that they dont get the result with what they gave in, instead one gets output with the name another enterted.
To make it more clear..
Suppose C1 enters "Adam" as input to the servlet to get an output "Adam belongs to Section C "
C2 enters "Lisa" as input to the servlet to get an output "Lisa belongs to Section C "
C3 enters "Ted" as input to the servlet to get an output "Ted belongs to Section C "
What happens sometimes is that when C1, C2,C3 enter their value at the same time, C2 and C3 get "Adam belongs to Section C " instead of "Lisa belongs to Section C " and "Ted belongs to Section C "
When can such a thing happen?? Does servlet cache in the server??
How come the value gets passed on to the other requests as well..
Any help is appreciated..

Are you using class level or object level variables in your Servlet class to store the user entered values? (Use only local variables unless you really know what you are doing).
Are you using ServletContext attributes?
As far as I know, except for these two scenarios, there is no other way that requests will share values.

Servlet caching in oc4j/orion

I'm making changes to my servlet yet they do not seem to be getting picked up, even when I restart orion. I have my classes, jsp etc in a war file under applications. Is there a servlet caching issue here and if so how do i solve it. I noticed an earlier posting about classes needing to be in a jar file to get reloaded, is something similar required for servlets?
Neil W.

Neil,
If you are in the development stage of your application probably you will not like to go thru the hastle of building the WAR each time your servlet or JSP is changed. Please look at the following link to how to deploy apps with Exploded Directory Format http://otn.oracle.com/docs/tech/java/oc4j/htdocs/getstart.htm#1027810. In this case each time your apps is changed you just change the timestamp on web.xml by either UNIX touch command or some other mechanism and OC4J will redeploy your new apps.
regards
Debu Panda
Oracle

Standard Servlet caching mechanism

Gurus,
Is there any standards on caching servlet reponse. Most of the application servers provide their own mechanism to cache servlet response.
I am looking for application server netural standards for caching servlet resposne. If there is no standards for caching available in any of the servlet > 2 releases, probably i would send an email to servlet specification guys to think on something like this.
Its lot of pain when you write code in some server and deploy it on some other server where the servlet caching response caching is suported.
Any help in this will be appreciated

Here is more explanation...
Suppose for an example, a servlet that accepts parameter(s) and queries the database and displays a html text, may be around 100 records. ok?
Next time when you make the same request with same set of parameters, the servlet excecutes the db query again and display the same result when it was intially called.
Now my question, is there standard mechanism to cache the servlet reponse at server side and when the request is made with same set of parameters, it would be served from the cache instead of making db call.
In addition to that, it should work under all the application server when you deploy
Let me know if this clear enough, or i can add more stuff in here.

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.

Servlet cacheing issue?

hi
i'm having a slight problem i believe may be due to cacheing.
i'm calling a servlet within a frame that displays a generated pdf file using certain values and so forth.
the problem is that it appears to be chacheing the servlet and never reloading it as it should given values change etc.
i'm using tomcat 3.3.1 and apache web server. i tried adding the following :
response.addHeader("Pragma", "No-cache");
response.addHeader("Cache-Control", "no-cache");
response.addDateHeader("Expires", 1);
to my servlet but that had no effect. adding the http meta equivalents to the frame-set page, also had no effect.
another interesting point is that this only occurs using the apache and tomcat combination. it doesn't happen using IIS and tomcat. could there be a setting in tomcat or apache i've neglected?? perhaps some other code to avoid this?
any help would be greatly appreciated.
thanks
Takis

use:
response.addHeader("Expires", 1);
instead of:
response.addDateHeader("Expires", 1);

Flushing the Servlet Cache or buffer(maybe) ^o^

Hi,
I wrote a few JSPs that use servlets and scriplets using import and include attributes to extract data from a database table. Everything works fine, except when I refresh the page the results are shown multiple times.
That is to say, the servlets seem to remember the previously generated values from the table and calculations, and displays it before showing the new results. I tried using the flush="true" attribute, but to no avail. After about 10 mins or if i restart Tomcat the servlets would clear the cache.
I am writing these JSp for a school assignment, and so far this is the part that I am having trouble dealing with. Is there a workaround for this? or is this an implementation error in my part? Any help would be appreciated. Thanks in advance!
Cheers,
-Shawn

Well thats interesting. I wrote a test Servlet program to see the newsbean output and I get the same problem now and It appends the old result. I realize that the trouble is not in the include statement, rather in the servlet itself.
I looked over the code to see what it could be, but couldn't catch it. But maybe you might see something different. So I will include the code for the TestServlet and the dependat classes. And Philip I appreciate your effort trying to help me out with this! : )
test Servlet class
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.ListIterator;
import java.sql.*;
public class NewsServlet
extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
NewsBean NewsPiece = null;
try
staffMembers = new NewsBean();
catch (SQLException ex)
//iterating through news list
ListIterator li = null;
try
li = NewsPiece.getNewsItem().listIterator();
catch (SQLException ex1)
String myNews="";
while(li.hasNext()){
NewsItem news = (NewsItem) li.next();
myNews += news.getTitle()+" \t"
news.getDescription()" \t"
+ news.getSubmitdate() +" \t"
news.getEndDate()" \t"
news.getAuthor()"<p>";
String docType =
"<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0 " +
"Transitional//EN\">\n";
out.println(docType +
"<HTML>\n" +
"<HEAD><TITLE>News</TITLE></HEAD>\n" +
"<BODY BGCOLOR=\"#FDF5E6\">\n" +
"<H1>News</H1>\n" +
myNews+
"</BODY></HTML>");
This is the newsbean class
import package.name.sqlAdapter; //This is used to simplify database connections
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.LinkedList;
public class NewsBean{
private static ResultSet results;
private static LinkedList newsItems = new LinkedList();
public NewsBean() throws SQLException{
//connect to DB
sqlAdapter sqlConnection = new sqlAdapter();
//Get Staff list
String query = "SELECT * FROM `news` ";
results = (ResultSet) sqlConnection.runCustomQuery(query);
public LinkedList getNewsItem()throws SQLException{
while(results.next()) {
//read in columns
String description = results.getString("description");
String title = results.getString("title");
String submitDate = results.getString("submit_date");
String endDate = results.getString("end_date");
//String author = results.getString("author");
String picture = results.getString("picture");
String id = results.getString("id");
//create NewsItem object and add to list
NewsItem news = new NewsItem(title, description, submitDate, endDate, picture, id);
newsItems.add(news);
return newsItems;
Here is the NewsItem Class
public class NewsItem
private String title;
private String description;
private String submitDate;
private String endDate;
private String author;
private String picture;
private String id;
public NewsItem(String Title, String Description, String SubmitDate, String EndDate,String Picture, String ID){
this.title = Title;
this.description = Description;
this.submitDate = SubmitDate;
this.endDate = EndDate;
//this.author = Author;
this.picture = Picture;
this.id = ID;
public static void main(String[] args) {
//test code here
public String getDescription(){
return this.description;
public String getTitle(){
return this.title;
public String getSubmitdate(){
return this.submitDate;
public String getEndDate(){
return this.endDate;
public String getAuthor(){
return this.author;
public String getPicture(){
return this.picture;
public String getNewsID(){
return this.id;

Servlet caches when it shouldn't

My Applet is sending my servlet a filename, the servlet the opens the file and send some info back to my applet. Now the problem comes when I want to open another file, the Servlet keeps on opening the first file I opened! The only way I get it to open the right file is by shutting down and restarting tomcat. How can I get around this? If tried putting this code in my applet after I declared the url, but it does nothing:
URLConnection con = url.openConnection();
con.setUseCaches(false);

This is the code for my servlet:
import java.io.*;
import java.io.File;
import java.util.*;
import java.net.*;
import javax.servlet.http.*;
import javax.servlet.*;
import java.util.Vector;
public class TestServlet extends HttpServlet {
     String file;
     String outputFile = "output.txt";
     PrintWriter out;
     Vector v = new Vector();
     String path;
public void doGet(HttpServletRequest req,
          HttpServletResponse res)
          throws ServletException, IOException{
     res.setContentType ("text/plain");
     out = res.getWriter();
     path = getServletContext().getRealPath("WEB-INF/textfiles");
     file = req.getParameter("name");
     readfile();
     for(int i=0; i<v.size(); i++)
     out.print(v.elementAt(i));
out.close();
public void readfile(){
     try{
     FileReader in = new FileReader(path+ File.separator + file);
          int c;
          while ((c = in.read()) != -1){
          char car = (char)c;
          System.out.println(car);
          Character obj = new Character(car);
          v.addElement(obj);
     }//while
     in.close();
     //outfile.close();
     }catch(IOException except){
     }//end catch
}//readfile
And this is how I call it in the applet:
String name = outField.getText();
try {
String host = getCodeBase().getHost();
URL url =
new URL("http://" + host + ":8080/servlet/TestServlet?name=" + name);
URLConnection con = url.openConnection();
con.setUseCaches(false);
BufferedReader in = new BufferedReader(
               new InputStreamReader(url.openStream()));
Anybody know what am I doing wrong?

Servlet cache

I have a html that use form tag that call a servlet, like this:
<FORM METHOD="POST"
ACTION="/servlet/xyz">
Where xyz is xyz.class that I compiled from xyz.java.
I use Netscape Web Server, how do I make the html to load the new
xyz.class
when the xyz.class is changed ?Regards.

http://knowledgebase.iplanet.com/ikb/kb/articles/4339.html
rob
Ketung Hsiao wrote:
>
I have a html that use form tag that call a servlet, like this:
<FORM METHOD="POST"
ACTION="/servlet/xyz">
Where xyz is xyz.class that I compiled from xyz.java.
I use Netscape Web Server, how do I make the html to load the new
xyz.class
when the xyz.class is changed ?Regards.

Preventing servlet output stream to flush

I increased the buffersize in the response object in order to make it possible for the entire jsp page to process before writing any output to the webclient.
BUT since I use dynamic jsp-includes I fail to accomplish this, since according to the JSP1.3 specification the output stream is flushed before processing a dynamic include instruction.
Is there a way I can make JSP to process the include and write output to buffer WITHOUT flushing it?
Regards, Jon

No I am using JSP 1.3. And I want to do the following:<%
for (int i = 0; i < 5; i++) {
// include("file_"+ i +".jsp");
%>This to include file_0.jsp up to file_4.jsp.
I assume the <jsp:include>tag is preprocessed hence only included once.

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...

Caching problem of servlet

Hi guys
We are facing this problem of caching within our project. The project aims to generate a html code to pick up some rich media ads details at random and displaying on the html file where the generated code is expected to be pasted. We developed two servlets, one which extracts the ads from the database randomly and then depanding on the ad type it calls the other servlet as src of an iframe, which in turn puts all code for displaying the rich media ads. The script which we are generating for the user to paste onto their pages is:
<script LANGUAGE="JAVASCRIPT" src="http://192.168.1.6:8080/advert_java/servlet/GetAdServlet?region=1&zone=1&type=nossi&cachevar=yes">
</script>First servlet (GetAdServlet) returns the javascript statements and thus is called using this generated code. 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 (BannerCode to be called);
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 comes when we run the html file containing the script tag mentioned above, and refresh our page, ideally it should pick the ads randomly and pass it on to RichMediaServlet.
I also try debugging both servlets. I called the getadservlet from javascript mentioned above and put debugging info in both the servlets, now for every refresh we do on the html side, we are getting a different random bannercode in adservlet but in richmedia when we print the bannercode received in querystring it is taking an older value which was displayed some time back and keeps on doing this for quiet a long time, making it look like some caching problem of RichMediaServlet.
Instead when we tried to put the same html <script> code into another servlet's doGet, everything seems to be working fine.
i have also used the following code to prevent the caching on 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>');");I request you all geeks to try and help me to your best. The project is at its final stages and in high urgency now.

i think the caching is being in the browser, with the iframe.
You should try passing a random param to the servlet in the iframe URL, something like:
var a = Math.random() * 10000000; //for example
out.println("document.write(\"<iframe src='" + iframeURL +"&rand="+a+"' height=" + hheight +" width="+ wwidth + " SCROLLING=no FRAMEBORDER=0 MARGINWIDTH=2 MARGINHEIGHT=2 onfocus='window.focus(); return iframeFocus()'>\");");
out.println("document.write(\"</iframe>\");");
...It should force the browser to ask for the servlet again
hope this helps...

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

Configuring Servlet Result Cache

Greetings.
I am trying to configure the iAS servlet result cache feature under iAS 6.0 SP2. I have the following entry for a servlet in my ias-web.xml file:
<servlet>
<servlet-name>MessageRouter</servlet-name>
<guid>{CAC10848-06B4-1C5F-848B-08002085745B}</guid>
<validation-required>false</validation-required>
<servlet-info>
<sticky>false</sticky>
<encrypt>false</encrypt>
<number-of-singles>10</number-of-singles>
<disable-reload>false</disable-reload>
</servlet-info>
     <caching>
          <cache-timeout>300</cache-timeout>
          <cache-size>10</cache-size>
          <cache-criteria>Xml</cache-criteria>
          <cache-option>TIMEOUT_LASTACCESS</cache-option>
     </caching>
</servlet>
However, it does not appear to be caching the results of this servlet because my request takes about 10 seconds to run (it's a database query). I would expect that subsequent requests would return results much faster than 10 seconds if the servlet results are in fact cached.
So, I am hoping that someone can help me with the following questions:
1. An example ias-web.xml with a cached servlet.
2. Any instructions on how to monitor from iASTAT or logs or something so I can see that the servlet result is read from iAS cache.
Thanks
Jeffery Cann

Check out the samples included with the appserver. There is a servlet caching sample that includes four different examples of deployment descriptors.
Here is the servlet tag from the default:
<servlet>
<servlet-name>ServCache</servlet-name>
<guid>{DD6402C6-CC11-1AA1-CF6F-080020CFEAC8}</guid>
<validation-required>false</validation-required>
<error-handler></error-handler>
<servlet-info>
<sticky>true</sticky>
<encrypt>false</encrypt>
<number-of-singles>10</number-of-singles>
<disable-reload>false</disable-reload>
<caching>
<cache-timeout>900</cache-timeout>
<cache-size>64</cache-size>
<cache-criteria>inputtext</cache-criteria>
<cache-option>TIMEOUT_CREATE</cache-option>
</caching>
</servlet-info>
</servlet>
The KXS log (assuming that you have info messages) will report servlet cache hits.
David
Shameless plug for my iAS book : http://www.amazon.com/exec/obidos/ASIN/076454909X/
P.S.
I just realized that the caching sample was only added in sp3. Even if you don't upgrade your server (the functionality is unchanged) you may want to download sp3 so that you can check out the sample. The sample goes into a reasonable amount of depth about this feature.

Prevent servlet caching

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