Writing applets that read files hosted on a webserver.

I have a java applet that I need to be able to read files on the webserver. IE open and render images. I know ultimately the user will end up downloading these images that are hosted on the websserver, but the java applet is set to read from it's local directory, for example, when I open up a text files, I use the path someFolder\someFile.txt. If the applet was placed in the same folder as someFolder on the webserver, how would I set it up to read from there opposed to on the machine executing the java code? Would I have to force the user to download all the resources, in thus case, wouldn't I need to to have the applet signed?

++++ to everything by malcolmmc (use class.getResource())
Jeremy.W wrote:
...I could perform a CRC check and compare the archives with the ones on the server, but it still means I'd need to compress the archives manually every time an update is made to the files on the server.I am not sure whether you are concerned with the effort of doing this from your side. If so, use Ant to make your ..war file or whatever and just upload it (and restart the server?).
If it is the archives (Jar or Zip) updating on the client that is your major concern, then I would definitely recommend the JNLP based option, which gives the client not only automatic update (the JWS client manages the time checks with the server), but if you want to go that far, direct programmatic access to the download API. I made a crude example (never properly finished) of downloading resources using the JNLP APIs DownloadService. (Though the standard 'auto-update' is known to be quite effective).
Oh, and.. Of course, if you have a Java enabled server, the download servlet is known to be best for updates, incremental or otherwise.
Does this applet really need to be embedded in a web page at all? JWS has offered these things to free-floating applets since Java 1.2, it is only recently an embedded applet could hook into the JNLP API.
As to the 'Zip' archives of resources. Some points:
1) It pays to split them up, especially if resources are likely to change frequently in one, but rarely for others. If you do that, webstart ensures the user only downloads the updated Jars. The only way to achieve a class/resource refresh in a conventional embedded applet ('plugin1') was to flush the class cache which would force refresh of all classes/resources.
2) Splitting the archives according to type of resource can provide benefits in that the Jars can have different compression levels appropriate to the format.
3) I would recommend deploying all resources, whether classes or other resources, in Jar and not Zip files. Sun has decided that no Zip will be checked to see if it is digitally signed, so Zip archives can cause problems for apps. which might need extended permissions (if it ever comes to that).

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Trying to write an applet that reads/displays a file from a remote server

Hey all,
I'm trying to make a little applet that launches from a browser that allows me to read a file from a server, reads it line by line and displays each line, and continues to read/monitor the file until I get a specific line of text.
I've tried to do some code and although I can read the file (and display it), I can't seem to detect the end string (the if statement that tests if the line == "--END--" seems to have no effect, i.e. constant false).
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2. Go and read the X section in the Y tutorial.
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import java.util.*;
import java.io.*;
import javax.swing.*;
import java.awt.*;
import java.net.*;
public class FaxTest extends JApplet {
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use tmp.equals("--END--\n") instead of tmp == "--END--\n"
The == means does tmp reference the same object as "--END--\n" which will probably never be true. Using the equals method means does tmp contains the same characters as "--END--\n"

Java Applet that reads from file

I'm quite new to java, I'm fiddling around with it for a nonprofit organization.
I have a java program that reads from a specified file and generates output but my final goal is a search box on the website that will take user input, run it through my program which searches through a prespecified file, and generate output.
I'd appreciate any help.

What can I do with this? I need it to be a String because I'm breaking it down to Tokens.
Thanks,
-Grant
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String MyArray[] = new String[5000];
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When downloading itunes updates, i get an error that reads file folder for itunes media has an invalid character

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This happens if the file is no longer where iTunes expects to find it. Possible causes are that you or some third party tool has moved, renamed or deleted the file, or that the drive it lives on has had a change of drive letter. It is also possible that iTunes has changed from expecting the files to be in the pre-iTunes 9 layout to post-iTunes 9 layout, or vice-versa, and so is looking in slightly the wrong place.
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Security manager - applet - write/read files

Hi.
I've been trying to built a SecurityManager to allow my java applet to construct a file (*.txt or *.doc) on the server (webhosting provider) it came from. Unfortunately when I use the setSecurityManager method to set my Security Manager as the default Security Manager for that specific applet, the applet throws a SecurityException. It wouldn't allow me to change the Security Manager.
I want to change the default Security Manager so that my applet can have permission to read and write to the specified file (*.txt or *.doc). I don't want to save any kind of files on the host computer even if I can do that, I only require to save my file (*.txt or *.doc) to the computer from were the applet's classes came from.
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If there is a security manager already installed, this method first calls the security manager's checkPermission method with a RuntimePermission("setSecurityManager") permission to ensure it's ok to replace the existing security manager. This may result in throwing a SecurityException. Thus I think that you need to grant the setSecurityManager permission to your current SecurityManager to be able to replace it.

Reading file in Applet.

Hello All,
i am trying to read a file in applet. i have created a applet that reads file and prints its content. it works fine on local system but when i publish this applet in web server it gives such exceptions.
java.security.PrivilegedActionException: java.lang.reflect.InvocationTargetException
     at java.security.AccessController.doPrivileged(Native Method)
     at sun.plugin.liveconnect.SecureInvocation$2.run(Unknown Source)
     at java.security.AccessController.doPrivileged(Native Method)
     at sun.plugin.liveconnect.SecureInvocation.CallMethod(Unknown Source)
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     at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
     at java.lang.reflect.Method.invoke(Unknown Source)
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     at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
     at java.lang.reflect.Method.invoke(Unknown Source)
     at sun.plugin.javascript.JSClassLoader.invoke(Unknown Source)
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Caused by: java.security.AccessControlException: access denied (java.io.FilePermission C:\reading\run.bat read)
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     at java.security.AccessController.checkPermission(Unknown Source)
     at java.lang.SecurityManager.checkPermission(Unknown Source)
     at java.lang.SecurityManager.checkRead(Unknown Source)
     at java.io.FileInputStream.<init>(Unknown Source)
     at readFile.showContent(readFile.java:38)
Can some body say whats going on?
I am stuck over here.
Any help will be appreciated.
Regards
Jaya N pasachhe.

If you are surfing the web, and you click a link to a page that you don't know, you don't want some unknown Applet to start and be allowed access to your local harddrive or printer.
Therefore, Applets ran by the browser, run in a so-called "sandbox". Read about it.
The solution is to "sign" the applet's jar.
see http://www-personal.umich.edu/~lsiden/tutorials/signed-applet/signed-applet.html
and http://forum.java.sun.com/thread.jspa?threadID=174214

Applet reading files in in web server eg geocities

hi ,
i have an applet that reads files i have created in a web server. when i try to run the applet in , internet explorer i get an error message
java.io.FileNotFoundException: nic.txt (The system cannot find the file specified)
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Applets work on the clients computer, not the server. Your applet is >trying to read nic.txt from your computer. Can't be done easily, you'd >need your own serverprogram to do the reading and pass the data to the >client... let me clarify afew points
the applet is on a webserver eg. geocities.
the file is also on the same directory as the applet .class file.
so everything is on the web server,.

OutOfMemoryError in applet that just uploads files

I have an applet that uploads files to the server and I'm seeing an OutOfMemoryError when the files are too large for the available heap size of the JVM. The code that uploads the files is rather straightforward:
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Any help would be much appreciated.
Thanks,
-B

Found the solution:
http://forum.java.sun.com/thread.jspa?threadID=418441&messageID=2816084
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5026745

Applet + Read File??????

Hello security gurus:
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executed directly from the appletviewer or the browser but when I load my program and it's dependencies in a webserver such as tomcat or apache it chokes on applet security exceptions. If someone could help I could stop
beating my head on the desk where my workstation resides.
Thanks, Ian

Hi Bakrudeen,
I�m a newbie into Java Applets ( so, Java too ), I work with C and C++, but now I need to do somethings using Java. One it�s that I need to do a Applet that read a xml file that�s into my webserver, in the same direcotry that my .class files are. First, I did a java class that run stand alone, it read the file perfectly, after I did a class that extends the applet class, but it didn�t found. Reading your e-mail, I had some questions, than, can you explain better your ideas ? Because, I have the plugins in my machine ( not in the server, the server doesn�t have anything about java, only the Apache server, my webpages and applet classes ), but I can�t read the file ? Another question is: how can I do to see the exceptions messagens to try looking for my errors ?
See below the source code that I�m trying to use:
import javax.swing.*;
import java.awt.*;
import java.applet.*;
import java.net.*;
import java.io.*;
import org.w3c.dom.Document;
import org.w3c.dom.*;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
public class WS10Parser extends Applet {
public int finished;     // 0 - n�o encerrado
// 1 - encerrado
// 2 - erro
private JanelTexto janela;
public void init() {
janela = new JanelTexto();
public void paint(Graphics g) {
//          g.drawString("Welcome to Java!!", 50, 60 );
* Fun��o para leitura do arquivo XML
* Parametros:
* - Nome do arquivo XML a ser lido
* - Nome do Dispositivo a ser lido
* - Modo de leitura do arquivo
*     - 1 L� somente dados referentes ao dispositivo identificado pelo Nome
*     - 0     L� informa��es de todos os Devices no arquivo
//     public void ReadFile(String FileName, String DeviceName, int Mode) {
public void ReadFile(String FileName) {
finished = 0;
URL url;
try {
url = new URL(getCodeBase(), FileName);
janela.AddText("File name: " + url.toString());
DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = docBuilderFactory.newDocumentBuilder();
Document doc = docBuilder.parse(url.openStream());
// normalize text representation
doc.getDocumentElement().normalize();
janela.AddText("Root element of the doc is " + doc.getDocumentElement().getNodeName());
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int totalDevices = listOfDevices.getLength();
janela.AddText("Total no of devices : " + totalDevices);
for(int s=0; s<listOfDevices.getLength() ; s++){
Node firstDeviceNode = listOfDevices.item(s);
if(firstDeviceNode.getNodeType() == Node.ELEMENT_NODE){
Element firstDeviceElement = (Element)firstDeviceNode;
NodeList firstNameList = firstDeviceElement.getElementsByTagName("name");
Element firstNameElement = (Element)firstNameList.item(0);
NodeList textFNList = firstNameElement.getChildNodes();
janela.AddText("Device Name : " + ((Node)textFNList.item(0)).getNodeValue().trim());
NodeList lastNameList = firstDeviceElement.getElementsByTagName("timestamp");
Element lastNameElement = (Element)lastNameList.item(0);
NodeList textLNList = lastNameElement.getChildNodes();
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janela.AddText("Total no of channels: " + totalChannels);
for(int cont = 0; cont < listOfChannels.getLength(); cont++) {
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if(channelNode.getNodeType() == Node.ELEMENT_NODE) {
Element channelElement = (Element)channelNode;
NodeList tagList = channelElement.getElementsByTagName("tag");
Element tagElement = (Element)tagList.item(0);
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janela.AddText("Tag: " + ((Node)textTagList.item(0)).getNodeValue().trim());
NodeList valueList = channelElement.getElementsByTagName("value");
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NodeList textValueList = valueElement.getChildNodes();
janela.AddText("Value: " + ((Node)textValueList.item(0)).getNodeValue().trim());
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}//end of for loop with s var
finished = 1;
}catch (SAXParseException err) {
janela.AddText("** Parsing error" + ", line " + err.getLineNumber() + ", uri " + err.getSystemId());
janela.AddText(" " + err.getMessage());
finished = 2;
}catch (SAXException e) {
Exception x = e.getException();
((x == null) ? e : x).printStackTrace();
finished = 3;
}catch (Throwable t) {
t.printStackTrace();
finished = 4;
private class JanelTexto extends JFrame {
private JTextArea ta;
public JanelTexto() {
super("Teste Applet Novus");
Box b = Box.createHorizontalBox();
ta = new JTextArea(20, 30);
b.add(new JScrollPane(ta));
Container c = getContentPane();
c.add(b);
setSize(425, 200);
show();
public void AddText(String Text) {
ta.append(Text + '\n');
Thanks

Applet read file on web

Can applet read file on web?
I try to write an applet that read the file on web i.e. http://lcoalhost:8080/test.txt
The HTML page contain the applet is placed on http://localhost:8080
URI URItemp= new URI("file:///test.txt");
File Filetemp = new File(URItemp);
BufferReader in = new BufferReader(new InputStreamReader(new FileInputStream(Filetemp)));the above cannot work
Error : access denied (java.io.FilePermission \test.txt read)
And then I add
FilePermission fp = new java.io.FilePermission("file:///test.txt", "read");still cannot work
Cound anyone tell me that is possible to do what I want to do?
If yes, how?
Thanks!!

Applets are downloaded from web servers and execute on the client machine.
Therefore they have no access to the web server file system, signed or not.
They could have access to the client file system (the machine where they run),
but for security reasons only signed applets have this privilege.
So to answer your question, you sign if you want to access client files.
To access web server files, you don't need to sign the applet, but you need
to provide some method of accessing files remotely, for instance:
- Files published for the web can be read using HTTP
- Files can be read or writen with the help of an FTP server on the same machine as the web server
- A servlet running on the HTTP server can collaborate with your applet to exchange files

Applet accessing local files under Vista

I have a signed applet that accesses files on the client machine. This applet is not able to open files when running under Windows Vista (I get an "Access denied" message). I found that in C++ there is a function called GetTempPath, which returns a path to a directory where and OCX control can access files. So here is my question:
Is there some Java function that will return the path to the directory mentioned above?
Thanks for your help.

Sorry, DrClap, but...
Post 1: "I have a signed applet that accesses files on the client machine. This applet is not able to open files when running under Windows Vista (I get an "Access denied" message)." While he mentions temp files/dirs, that is not, IMO the issue, because...
Post 6: "Under these OSs [XP, 2000], my applet uses a directory called c:\program files\mydir. This applet is not able to access files in the same directory under Windows Vista, access is denied in this case." The specified directory is not a "temp" dir as typically returned by the system parameters that I've ever seen, so I'm assuming he's using this explicitly. In which case, access is denied writing to it. In which case, it appears to be a signed applet permission issue.
While the java.io.tmpDir system param may be giving an issue to, that doesn't seem to be the key point in what I'm reading. Otherwise it's not written entirely clearly.

Application Design,Java Read Files,Merging Files,Outresults

Read all files from a folder in the same directory
Files with the same name but different extension
On .txt extensions,count the number of words,the start and end offset of each word,output into a textfiles
Merge a1,a2,ann,rel(other file extensions),on read each line,and store it into a data-structure
Join results of 3,4 and output into a new folder <previousfolder>_result
What are the operations that I can use to achieve this with java?
How can I achieve this with java?

Welcome to the forum!
When you post your class assignments you should provide the class name, teacher name, textbook used and the exact instructions for the lesson as presented by your teacher.
>
Read all files from a folder in the same directory
Files with the same name but different extension
On .txt extensions,count the number of words,the start and end offset of each word,output into a textfiles
Merge a1,a2,ann,rel(other file extensions),on read each line,and store it into a data-structure
Join results of 3,4 and output into a new folder <previousfolder>_result
What are the operations that I can use to achieve this with java?
How can I achieve this with java?
>
Have you covered all of those concepts in your class?
Did you ask you instructor to explain any of the steps you did not understand?
Have you written, compiled and run any Java classes at all yet?
Post the code you have written so far, explain what it does and what it does wrong and you will get advice about how to find and fix the problem.
Break the problem into pieces. Start by writing code that
>
Read all files from a folder in the same directory
Files with the same name but different extension
>
Post the code and the results it gives you.
Good luck with your assignment. Remember, the teacher is there to help you if you get stuck.

Reading file from FTPs

I have to read from different locations(FTP Servers) if there are any new files I have to transform those to my ftp, If I place a new file in my ftp it has to go to the other ftps.
Can i achieve this with a single ESB service?
I believe I can do it using two ESB services.
Can I read .xls files using FTP adapter and transform them to XML??
Any suggestions please, it is very urgent
Thanks
V Kumar

Define an ESB service that:
- read file with FTP adapter in ESB
- From your services it writes the file to the other FTP location.
Create the services for all ftp location to want to touch.
Marc

Reading from the Applet's JAR file.

Is it possible to read a file stored in the jar file that the (unsigned) applet is being executed in? I have a line that goes like (in is just an InputStream):
in = getClass().getResource( "/exercise.xml" ).openStream();
and then, in another class, i do (bulider is an instance of javax.xml.parsers.DocumentBuilder, created from the DocumentBuilderFactory class):
doc = builder.parse( in );
but this always results in a security exception (works fine from the applet viewer). I tried specifying the full path to the .jar file as the codebase, but got the same results. I have not tested this from an actual web server, i am only opening the .html file directly in IE.
Due to the nature of the application, it is not possible to host the file seperately on a webserver.
It seems to me that there is no reason an applet shouldnt be allowed to load a file from the .jar it is executing in, could this simply be a problem of the file being local, and thus linked to from a file:// tag?
Thanks for any help.
Thomas Stephens

Hi Guys
I have figured out this problem. It's got to do with classloader.
Applet uses a separate classloader. So using the static getSystemResource(),
we never get contents from applet jar files. The following will work nicely.
It is noted that you must loacate the applet classloader as in the first line
and use the non-static method getResource();
ObjectInJar obj = new ObjectInJar(); // create an object with a class in the jar file.
ClassLoader cl = obj.getClass().getClassLoader();
InputStream stream = cl.getResource("your_filepath_in_jar").openStream();
Cheers.

Writing applets that read files hosted on a webserver.

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