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.
Thank you!

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.

Similar Messages

Write / read files to RAM memory

Dear all,
I want to write a text file to RAM memory and after read it from RAM memory.
Why? Because, I want to read my text files quickly, in short time.
if I use default method for reading files it take long time for reading the file and for write the file.
But, if I use write / read files to RAM memory, I can read my files quickly and read my files from RAM for processing and write my files to HDD.
Can you help me?
I searched on the Internet this problem and I did not find any one solution.
From my searching on the Internet, I understand that Java can not do that.

The problem with this program is that it load 1 minutes, but I want to load a second.
Here is my java code:
import java.io.*;
public class File {
public static void main(String[] args) {
// Start to reading the file
      try{
    FileInputStream fstream1 = new FileInputStream("big.txt");
    DataInputStream in = new DataInputStream(fstream1);
        BufferedReader br = new BufferedReader(new InputStreamReader(in));
    String strLine;
    while ((strLine = br.readLine()) != null)   {
// Start to replacing method
    String strreplace = "%";
    String result = strLine.replaceAll("a", strreplace);
// End of replacing method
// Start to writing to file
      try{
    FileWriter fstream2 = new FileWriter("out.txt", true);
        BufferedWriter out = new BufferedWriter(fstream2);
    out.write(result); // Write to file the result
    out.close();
    }catch (Exception e){
      System.err.println("Error: " + e.getMessage());
// End of writing to file
    in.close();
    }catch (Exception e){
      System.err.println("Error: " + e.getMessage());
// End of reading from file
} // Here is the end...Please to do the following steps:
1. Copy my code;
2. Download text file from: [http://norvig.com/big.txt|http://norvig.com/big.txt]
3. Open the text editor and select all text (Ctr+A) and dublicate the text 10 times for creating a big text file (30-40 MB);
4. As a java developer, You know what to do next.
I'm waiting your solution.
Thanks in advance!

Applet write to file on server

Despite people's insistence that this is in the tutorial or faq, I find that it is not. Also, I have gotten conflicting information about this so I'd like to know the real answer. I want to have an applet that loads in the user's browswer, collects some data, then writes the data to a file on the server from which the applet was loaded.
Here is what I have managed to accomplish (using my Win98 comp and Unix server):
from just loading the applet on my computer and using relative file name to write - it made a file on my desktop (not the right place) but with the correct information
on my comp and using absolute windows file name - it made the file in the right place and with correct information
from trying the applet over the web on a server that allows you to write to files using both relative and absolute file names - acted dead when I pushed the button that would make it write to a file, and it didn't execute the "catch."
I really want this to work since I want the applet to be the user interface and the applet is preferred to javascript or something else because of the nature of what I'm doing. Also, we were going to use a SQL database. I know Java has an interface with SQL but could I get my applet to communicate with our SQL database on the server directly or are we going to have to make another script for it to go through?
thanks

The following is a duplicate posting in reponse to similar question:
http://forum.java.sun.com/thread.jsp?forum=4&thread=200482&start=0&range=30#735223
In short, you cannot write to a server without help from servier-side software such as a servlet, cgi, ASP, etc.
If you go with something like an Oracle database on your server, it's a non-issue because the seucirty aspects are taken care of for you.
V.V.

Java applet writes to file on client, no signing necessary

Hi,
I wonder if this is a feature or bug:
I download and execute in my browser an unsigned applet/jar myCharts.jar from server. The applet references classes from package org.jfree.chart, which are not packed in myCharts.jar downloaded from server, but are locally stored on client in jre/lib/ext/jfreechart.jar (and therefore JVM running the applet loads and uses these local classes from local jar).
The applet can write the file to client disk without any problem using classes from locally loaded jfreechart.jar. If I merge both jars into a big one and load it through network, file write access is forbidden.
I am using JRE 1.5.0.3 for Windows and default java_policy file with 2 permissions added:
permission java.lang.RuntimePermission "accessDeclaredMembers";
permission java.lang.reflect.ReflectPermission "suppressAccessChecks";
Is it a bug, or feature ?
According to my opinion these 2 permissions should not result in applet ability to write files using locally loaded classes.
Thanks for your answer
Martin

The following is a duplicate posting in reponse to similar question:
http://forum.java.sun.com/thread.jsp?forum=4&thread=200482&start=0&range=30#735223
In short, you cannot write to a server without help from servier-side software such as a servlet, cgi, ASP, etc.
If you go with something like an Oracle database on your server, it's a non-issue because the seucirty aspects are taken care of for you.
V.V.

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).

Xcode writting/reading file problem

Hi,
im using xcode to compile in c language, but im having problem with files, writting/reading simply doesnt work (to be exact i have to say that i copied source code to dev-c++ on windows platform to check the code and it works normaly as it should) any suggestions?
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main (int argc, const char * argv[])
char tekst[]="tujesttekstktorychchcezapisacdopliku";
          char tekst2[20];
FILE *plik;   /*r=read, w=write, rwx-obydwachyba, wb-tryb binarny*/
          if ((plik=fopen("text", "w"))==NULL)
printf("plik nie zostal otworzony");
          fprintf(plik, "%s" ,tekst); /*wpisanie tekstu*/
          fscanf(plik, "%s",tekst2);
printf("tekst2: %s\n", tekst2);
          if (fclose(plik)!=0)
printf("blad przy zamykaniu");
    printf("Hello, World!\n");
    return 0;
the result of this program is "hello world" ONLY.
file is clean, same thing with test2 variable.
in copied code opening mode is "w" but ive checked almost all options ofc including binary file modes (both doesnt work)
any suggestions?
Message was edited by: Entwu

while( (len = in2.read(b,0,1024)) != -1 )
bytcount=bytcount+1024;
inFile.write(b,0,1024);
} This is where you go wrong ... suppose you're reading, say 100 bytes instead of the maximum 1024;
you're still writing 1024 bytes instead of those 100 bytes; your 'bytcount' goes berzerk too. Have a
look at this -- while( (len = in2.read(b,0,1024)) != -1 ) {
   bytcount=bytcount+len;
   inFile.write(b,0,len);
} kind regards,
Jos

Write/read file in OOP

Hello,
I have to make class that reads/creates tdms file
I know OOP concepts from C++ and I ve seen write and safe class to file example in labview but I have no idea haw to make it and what are benefits of using OOP in this case..
I thought about creating privete methods to write and read data from obiect and then creating public methods to set path filename etc.
but I don't know haw to write obiect to tdms file
Any help appreciated

Dr. Damien has been working to naswer your question and his series on LVOOP file I/O are indexed starting in post # 26 here.
It is a multi-part series.
In volume 8 he posted this Domaion model.
Have at it.
Post up Q's in those threads. WE really need a OOPer to review and comment.
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

Error 43 when accessing LabVIEW 2009 write/read file functions through the web server functionality

Is there any way around to avoid Error 43, "Operation cancelled by user" when using Web server?
I am using the example VI:s RemotePanelMethods-Server.vi and RemotePanelMethods-Client.vi to acces the MainGUI.vi from my workstation to a lab computer. * LabVIEW 2009 is installed in both machines.
* MainGUI.vi is wired to the VI access list in the Server VI but it also contains a hierarchy below that isn't, is this a problem?
* Several functions in MainGUI calls file read and write operations
The problem ocurrs when file read/write operations with no preselected path are selected through the Client. The traditional popup window requesting the file to read or write is never seen in the Client, but only the Error 43.
Thanks in advance

See this

About write read file

I have log file, maximum 500kb, every 30 sec to the end of file I saveing new information and if filesize willbe bigger than 500kb I have to erase older string information in the begin of file and up hole file. How did this very fastly because if lost power file willbe bad. My code doesnt work.
public String ReadLn(InputStream InData) {
          int i = 0;
          int ch = 0;
          String line = "";
          try {
               while ((ch != -1) & (ch != 10)) {
                    ch = InData.read();
                    line += (char) ch;
          } catch (Exception e) {
               return null;
          if (line == "")
               return null;
          else
               return line;
/////Inserting new information
FileConnection fconn = (FileConnection) Connector.open(file,Connector.READ_WRITE);
               if (!fconn.exists()) {//file is present
                    return;
               OutputStream OutData = fconn.openOutputStream(fconn.fileSize());
               OutData.write((record+endline).getBytes());//record new information
               OutData.flush();
               OutData.close();
               OutData = fconn.openOutputStream();//seek to begin
               int ch = 0;
               InputStream InData = fconn.openInputStream();
               String read_ln=ReadLn(InData);//read first line
               String data = "";
               byte buffer[] = new byte[1024];
               while ((ch=InData.read(buffer))!= -1) {
                    data = new String (buffer);
                    sendline(data);
                    OutData.write((data).getBytes());
               fconn.close();
               OutData.flush();
               OutData.close();
               InData.close();

Thanks for all. I will try to use RMS its more effectivity and simple to use and economy memory than txt file.

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)
Caused by: java.lang.reflect.InvocationTargetException
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
     at java.lang.reflect.Method.invoke(Unknown Source)
     at sun.plugin.javascript.JSInvoke.invoke(Unknown Source)
     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)
     at sun.plugin.liveconnect.PrivilegedCallMethodAction.run(Unknown Source)
     ... 4 more
Caused by: java.security.AccessControlException: access denied (java.io.FilePermission C:\reading\run.bat read)
     at java.security.AccessControlContext.checkPermission(Unknown Source)
     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

How applet write file in local system by URL instead of FileOutputStream()

hi,
how can applet write a file in local system through URL instead of FileOupStream()
plz.....plz.....plz......
URL url = new URL(" file://c:/temp.txt");
in this url how applet can write
plz....

URL uses http to cummunicate, this means you can send and receive data using the http
protocol.
The OS doesn't do anything with this, you need a http server to interpret these messages
and take appropriate action (with server side script or CGI).
So if the client has a http server installed and has server side script thad does
something with your http request (that's what a url does) than it is possible.
Since both having a http server , server side script and or CGI have nothing to do with
signed applets I will not answer your question here.
But the mail reason I won't answer it is because it makes no sence to use a URL to write
to the local file system.

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)
does anyone have any solution to this problem. do i need a policy file and if i do where do i put it.

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,.

Applet write file on coming server without servlet

Hi, I have an applet that needs to write a new file on the server that's LOADED FROM. Here are my questions:
1) can the applet write this file WITHOUT using a servlet on the server side?
2) if it's possible, could someone send me an example to explain how to do it?
Thanks in advance, have a nice day

1) can the applet write this file WITHOUT using a
servlet on the server side?No,it can't. Well, on the server is not necessary to
have a java servlet but you should have "something"
that can receive your data, understand it and save it.
A small PHP script is enough.
Hope this help

HP Protecttool Security Manager

Dear Sir
i have intalled hp protecttool security manager but it gives compitibality essue error.
can you please solve my problem or to send me another link of software download for windows 8.1.
Thank You

Hi @MF3,
Thank you for your query.
I understand that you getting an incompatibility message when trying to install HP Protect Security Manager.
Please read this post by Advice for asking the "Very Best Question by @ThatGarenGuy
To begin with I would need more information.
What is your exact model of HP notebook?
How Do I Find My Model Number or Product Number?
What Operating System are you running?
Regards
Sparkles1
I work on behalf of HP
Please click “Accept as Solution ” if you feel my post solved your issue, it will help others find the solution.
Click the “Kudos, Thumbs Up" on the bottom right to say “Thanks” for helping!

Write a file on the local system with an applet

Hi,
I am programming a user interface using HTML and now I would need an applet to write parameters into a plain text file.All this running on the same machine,with no network connection at all,and with I.E.
All my attempts have failed because of security reasons,but I thought it was possible to write a file on the local machine where the applet source is.
Can someone help me ? Please note that I am not a confirmed java user,so be as detailed as possible in your response !
Thanks a lot !
Sebastien

pls go to ur jdk.13\bin and type POLICYTOOL.
Click Add Policy Entry.
Click Add Permission
From the Listbox select ALLPermission and Click OK.
Then Click Done.
Then from the menu bar,
File -> Save As
then give the file name as .java.policy in ur home directory(c:\winnt\profiles\urname\.java.policy).
close the window.
these are the steps to give all permission.

Security manager - applet - write/read files

Similar Messages

Maybe you are looking for