Java

How to determine given file is a class file?

19-Jul-10 23:50

Thanks A Lot Mr.Nagy For ur valuable time to my answer.

Regards
Yogesh

glitteringsound13-Jul-10 20:43

glitteringsound

13-Jul-10 20:43

Hello,

I need to determine that whether given file is a class file or not? Perhaps I may change the extension to .exe/.xml or some other . I need to dtermine that given file if a class file will be parsed differently and if it would be some other, it'll be parsed in that manner.

How can we determine by reading class file format if, How can we read programatically class file format?
Regards
Usman

Cedric Moonen13-Jul-10 20:53

Cedric Moonen

13-Jul-10 20:53

What are you trying to do exactly ? What is the reason why you want to do something like that ?

Are you talking about .java files ?

glitteringsound wrote:
How can we read programatically class file format?

A class loader does that for you.

Cédric Moonen
Software developer

Charting control [v3.0]
OpenGL game tutorial in C++

glitteringsound13-Jul-10 20:56

glitteringsound

13-Jul-10 20:56

I need to just read and parse programatically Java class file header. So that I can determine weather its class file or not. I need that one to determine in my case. Possibly not in usual cases but just in my case.

Cedric Moonen13-Jul-10 21:00

Cedric Moonen

13-Jul-10 21:00

glitteringsound wrote:
I need to just read and parse programatically Java class file header.

What do you mean by header ? Confused | :confused:

But you still didn't answer my question, you merely repeated your first post: what is the reason why you want to do something like that ? Your request seems really akward, so it would help a lot to understand your question if you provide the context.

Cédric Moonen
Software developer

Charting control [v3.0]
OpenGL game tutorial in C++

glitteringsound13-Jul-10 21:12

glitteringsound

13-Jul-10 21:12

Respectfully
Sir,

I am working on app (kind of framework) which parse and extract function signatures and populate them on GUI. This needs to be first determine weather given file is a class file, Win32 File or COM Exe/DLL, Js or HTML file.(As in my case these all files can be made as input to framework by the user). This needs to parse given file format (probably headers)first to determine whether given file is within above mentioned context or not.?

Regards
Usman

Cedric Moonen13-Jul-10 21:19

Cedric Moonen

13-Jul-10 21:19

glitteringsound wrote:
I am working on app (kind of framework) which parse and extract function signatures and populate them on GUI.

Are the classes loaded in your application ? If yes, it would be much easier to use reflection to extract the information about the classes and methods (you won't need to do the parsing yourself, which is not an easy job).

glitteringsound wrote:
This needs to parse given file format (probably headers)first to determine whether given file is within above mentioned context or not.?

A class file is just a text file, so there's no "header" (like for instance in a binary file) containing info about the file. You could check the extension though (it should be .java).

Cédric Moonen
Software developer

Charting control [v3.0]
OpenGL game tutorial in C++

Upendra Jariya28-Jul-10 4:30

Upendra Jariya

28-Jul-10 4:30

Hope, this is something of your interest...

http://www.rgagnon.com/javadetails/java-0487.html[^]

The above code is in Java.

If you program for MFC, Windows API provides sufficient support for analysis of file headers.

Another useful information can be read here:

http://java.sun.com/docs/books/jvms/second_edition/html/ClassFile.doc.html[^]

~UJ.

How to install java Automatically if not present on Machine?

Richard MacCutchan13-Jul-10 22:15

Richard MacCutchan

13-Jul-10 22:15

A simple Google search found this[^] document containing all the detail you need?

It's time for a new signature.

002comp13-Jul-10 20:35

Re: How to install java Automatically if not present on Machine?I got some Info.See if guys can Help me out now.

13-Jul-10 20:35

Hello Friends
I want to install java on client machine if it is not installed through applet tag.I did through object tag but same I want to do through Applet tag.

Here is Object Tag:

<object id="viewer" classid="clsid:CAFEEFAC-0016-0000-0000-ABCDEFFEDCBA"
				codebase="http://java.sun.com/update/1.6.0/jinstall-6-fcs-windows-i586.cab"
				width=360
				height=557 >
				<param name="code" value="org.jdesktop.applet.util.JNLPAppletLauncher" >
				<param name="archive" value="http://download.java.net/media/applet-launcher/applet-launcher.jar,

This code automatically installs java but I want to do same through applet tag.I made some changes but it is not asking user to install.here is applet tag and please let me know wat do i need to change to install java?
Applet tag:
<applet
code="print_canvas3d.PrintCanvas3D "
codebase="http://java.sun.com/products/plugin/autodl/jinstall-1_4_2-win.cab"
width=360
height=557

archive="http://www.styku.com/wer.jar,
http://download.java.net/media/applet-launcher/applet-launcher.jar,

And one more prob is If I provide class name directly in code=pkg.classname then it is giving me right Id but If i use JNLPAppletLauncher at the same place then I am getting the Id of jnlpLaunched that I dont want ,I want the id of mine main class.How can i get?

Thanks & Regards
Yogesh

002comp15-Jul-10 2:24

Re: How to install java Automatically if not present on Machine?I got some Info.See if guys can Help me out now.

15-Jul-10 2:24

Hi Guys
I found Something and now I need ur help.Here is the code below,After using this code,It asks If java is uninstall but after that it is not loading my jar file,is it some path issue. Or if java is already installed on sytem then it loadds my jar file.

<applet 
code="org.jdesktop.applet.util.JNLPAppletLauncher " 
codebase="http://java.sun.com/products/plugin/1.3/jinstall-13-win32.cab#Version=1,3,0,0"
		

width=360
height=557

archive="http://www.sample.com/view/view.jar,
http://download.java.net/media/applet-launcher/applet-launcher.jar,
http://download.java.net/media/java3d/webstart/release/j3d/latest/j3dcore.jar,
http://download.java.net/media/java3d/webstart/release/j3d/latest/j3dutils.jar,
http://download.java.net/media/jogl/builds/archive/jsr-231-webstart-current/jogl.jar,
http://download.java.net/media/gluegen/webstart/gluegen-rt.jar,
http://download.java.net/media/java3d/webstart/release/vecmath/latest/vecmath.jar"
id="viewer">
<param name="codebase_lookup" value="false">
<param name="subapplet.classname" value="canvas3d.Canvas3D">
<param name="subapplet.displayname" value="My Java 3D Applet">
<param name="jnlpNumExtensions" value="1">
<param name="jnlpExtension1" value="http://download.java.net/media/java3d/webstart/release/java3d-latest.jnlp">
<param name="progressbar" value="true">
<param name="noddraw.check" value="true">
</applet>

Any Ideas Guys Now.
Regards
Yogesh

Ravi Sant19-Apr-11 3:55

Ravi Sant

19-Apr-11 3:55

Good, you found solution Thumbs Up | :thumbsup:

♫ 99 little bugs in the code,
99 bugs in the code
We fix a bug, compile it again
101 little bugs in the code ♫

Writing A file to server

002comp12-Jul-10 19:00

12-Jul-10 19:00

Hello Guys
i am trying to write a file to server with URLConnection.And here is the code below.I created one file at that location and with my code trying to write some thing but nothing is happening.I need some ideas.Or is it some issue with access to server on that file?

Code:

try {

    URL                url; 
    URLConnection      urlConn; 
    DataOutputStream   dos; 
    DataInputStream    dis;

    url = new URL("http://sample.com/test/file.txt"); 
    urlConn = url.openConnection(); 
    urlConn.setDoInput(true); 
    urlConn.setDoOutput(true); 
    urlConn.setUseCaches(false); 

    dos = new DataOutputStream (urlConn.getOutputStream()); 
    String message = "Yahoooooooo";
    dos.writeBytes(message); 
    dos.flush(); 
    dos.close();

    // the server responds by saying 
    // "SUCCESS" or "FAILURE"

    dis = new DataInputStream(urlConn.getInputStream()); 
    String s = dis.readLine(); 

//s is coming null.
    dis.close(); 


  
  } // end of "try"

  catch (MalformedURLException mue) { 
    addTextField.setText("mue error"); 
  } 
  catch (IOException ioe) { 
    addTextField.setText("IO Exception"); 
  }

Any Ideas guys.
Thanks & Regards
Yogesh

Gerben Jongerius13-Jul-10 2:04

Gerben Jongerius

13-Jul-10 2:04

For as far as I know webservers will not allow you to do this, at least not the way you want by opening or creating a file remotely and writing to it.

What you could do is write some servlet or JSP code on the remote server that accepts POST data and writes that to a file. You can then POST any content to that JSP / Servlet and store data that way.

EG:
server A has a servlet called /StoreFile
server B calls http://serverA/StoreFile

with POST data
fileName=file1.txt&data=<yourencodeddata>

002comp13-Jul-10 2:54

13-Jul-10 2:54

Hello Gerban
THanks for ur reply but I am reading the file from server in same way.Thats why I thought that writing is also possible in the same way.
And i got this solution from net.
Anyway,I will try ur way also but still If u know any other way then please let me know.

Thanks Again for ur replay.
Regards
Yogesh

Gerben Jongerius13-Jul-10 3:04

Gerben Jongerius

13-Jul-10 3:04

Reading should never cause you any issues, as this is the primary reason to have a webserver (get access to remote files).

The real question is why would you want to have unprotected writing to a webserver at all (which you are doing if you open a file on a remote server and just start writing in it). You would create a serious security risk.

If it is at all possible to write directly to a webserver from a remote connection then that will be a security setting on the webserver, and not on the Java side of things. So maybe you should also ask this question on some forums relating to Tomcat / Apache or whatever webserver you are running.

002comp13-Jul-10 19:47

Progressbar while some process is running

13-Jul-10 19:47

Thanks For ur Reply.
Yeah,I understand this would be a security risk.So I have to drop this way.
Thanks
Regards
Yogesh

002comp8-Jul-10 23:30

Re: Progressbar while some process is running

8-Jul-10 23:30

Hello Friends
I want to add progress bar moving while I am reading a file.
Any Ides Guys?

Thanks & Regards
Yogesh

David Skelly9-Jul-10 2:13

David Skelly

9-Jul-10 2:13

The simplest option is simply to start a progress bar running in indeterminate mode (i.e. the bar just bounces back and forwards to show you that something is happening), then load the file, then stop the progress bar when you are finished loading. That way you never need to worry about how big the file is.

The alternative is to get the length of the file before you start (create a File object, and call length()) then track the number of bytes you have read in as a percentage of the total and update the progress bar periodically. Don't update the progress bar too often (e.g. if you have a 2Mb file and you update the progress bar after reading every individual byte, you will be updating the progress bar over 2 million times, which is obviously not a good idea). Make sure you don't load the file on the Swing event handling thread, but make sure that you do update the progress bar on the EDT.

Or, you could use a ProgressMonitor, which is an inbuilt progress dialog that is sometimes useful.

Progress bar tutorial here:

http://download.oracle.com/docs/cd/E17409_01/javase/tutorial/uiswing/components/progress.html[^]

Re: Progressbar while some process is running

002comp9-Jul-10 2:35

9-Jul-10 2:35

Thanks A Lot.Mr David

Regards
Yogesh

File Object with URL?

002comp5-Jul-10 23:37

Re: File Object with URL?

5-Jul-10 23:37

Hello Friends
I am using file object to with URL path as parameter to pass filename to some function.But it is not creating File Object.I tried like this:

String filePath="http://test.com/folder/file.txt
File f = new File(new URL(filePath).toURI());

And like this too
File f = new File(new URL(filePath).getPath());

but it is crashing at this point.

Any Ideas Guys.
Thanks In Advance.
Regards
Yogesh

Richard MacCutchan6-Jul-10 1:47

Richard MacCutchan

6-Jul-10 1:47

yogeshs wrote:
but it is crashing at this point.

Any Ideas Guys.

Well perhaps if you showed the error that you received we may be able to help work out what is going wrong. However, I am not sure that you are allowed to create files on a client machine in this way.

It's time for a new signature.

Re: File Object with URL?

002comp6-Jul-10 19:57