JAR! . . .What is it good for?. . .Absolutely nothing :-)

[Oliver Wong]

Hi,

Well not quite; actually love JAR files, but why does the AppletViewer
(W2K
SUN JDK "something", at least) insist on asking for the .CLASS file *as
well
as* the .JAR file?

Is this *all* applet viewers? *all* html? or just something *my* code is
doing?

If I understand your complaint correctly, it's not all applet viewers:
mine doesn't additionally ask for a JAR file when I provide it a CLASS file
nor vice versa. I can't imagine how HTML or the Java source code itself
might trigger this behaviour in your applet viewer program, so I'd have to
say "no" to your other 2 questions as well.

Also why are there no hits on "noclassdeffounderror" on SUN's website?

I believe Roedy's site, mindprod.com, has a good overview of what to do
when you encounter a NoClassDefFoundError.
http://mindprod.com/jgloss/runerrormessages.html#NOCLASSDEFFOUNDERROR

In the attached *very short* code snippet, the EmpApplet class is
attempting
to invoke methods in the EmpClient class that has been built into the same
JAR file, but the only Typing that I can see (sorry not my code, but I'm
told this works on UNIX browsers) is: -

EmpClient client;

I've never heard the term "Typing" before. Based on context, I'm
guessing you're referring to the *declaration* of "client" as being of type
EmpClient.

I'm guessing that this declares "client" as an instance of the EmpClient
class, but doesn't EmpClient have to be Imported or something?

In your code (which I've snipped), both classes are in the same package
(which happens to be the default, nameless package). Classes which are in
the same package don't need to import one another to be visible to one
another. Note that it's generally considered bad practice to use the default
package. Recommended practice is to put classes in a package whose name is
based on a domain name which you own (this is sort of to provide globally
unique package names). So if you own "google.com", you could call your
package "com.google.mypackage", for example.

Either way,
EmpClient is not "inited" and the -debug gives me the noclassdeffounderror
and the browser makes no attempt to load EmpClient from the codebase.

So, how does one define a class? import?

The problem here isn't that the class isn't defined, but rather that it
class definition could not be found. Check out Roedy's recommendation on
fixing this (the URL again is
http://mindprod.com/jgloss/runerrormessages.html#NOCLASSDEFFOUNDERROR), but
be warned that this is one of the trickier problems to try to fix.

- Oliver

 

[Richard Maher]

Hi,

Well not quite; actually love JAR files, but why does the AppletViewer (W2K
SUN JDK "something", at least) insist on asking for the .CLASS file *as well
as* the .JAR file?

Is this *all* applet viewers? *all* html? or just something *my* code is
doing?

Also why are there no hits on "noclassdeffounderror" on SUN's website?

In the attached *very short* code snippet, the EmpApplet class is attempting
to invoke methods in the EmpClient class that has been built into the same
JAR file, but the only Typing that I can see (sorry not my code, but I'm
told this works on UNIX browsers) is: -

EmpClient client;

I'm guessing that this declares "client" as an instance of the EmpClient
class, but doesn't EmpClient have to be Imported or something? Either way,
EmpClient is not "inited" and the -debug gives me the noclassdeffounderror
and the browser makes no attempt to load EmpClient from the codebase.

So, how does one define a class? import?

Yes, I will google tomorrow but it's late and I'm old. . .

Regards Richard Maher

PS. Sorry for the school boy questions, but I honestly am RTFMing as well.

EmpClient Class
===========

import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.iutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;


public class EmpClient {
public static final String HOSTCHARSET="ISO-8859-1";
public static final byte [] CRLF = {'\r','\n'};
private Socket socket;
private String host;
private int port;
private BufferedReader in;
private OutputStream out;

public class Message
{
String type;
String message;
Message (String type , String message)
{
this.type = type;
this.message = message;
}
public String getMessage()
{
return message;
}
public String getType()
{
return type;
}

}
EmpClient (String host , int port)
{
this.host = host;
this.port = port;
}

public void open () throws UnknownHostException, IOException
{
socket = new Socket (InetAddress.getByName(host) , port);
in = new BufferedReader (new InputStreamReader (socket.getInputStream() ,
HOSTCHARSET));
out = new BufferedOutputStream (socket.getOutputStream());
}

public void close () throws IOException
{
try {
sendMessage ("99","");
} catch (IOException e) {
// close in any situation!
}
socket.close();
}

public void sendMessage (String type , String message) throws IOException
{
byte [] msgtype = type.getBytes(HOSTCHARSET);
byte [] msg = message.getBytes(HOSTCHARSET);

out.write(msgtype);
out.write(msg);
out.write(CRLF);
out.flush();
}
public Message readMessage () throws IOException
{
String wholemsg = in.readLine();

String type = wholemsg.substring(0,2);
String msg = wholemsg.substring(2);
return new Message (type , msg);
}
public void initEmployeeRead (String employee) throws IOException
{
sendMessage ("20" , employee);
}
public String readNextEmployee () throws IOException
{
Message msg = readMessage ();
if (msg.getType().equals("21"))
return msg.getMessage().trim();
return null;
}
}

EmpApplet Class
============

import java.applet.Applet;
import java.io.IOException;


public class EmpApplet extends Applet {
EmpClient client;

public void init ()
{
String host = getParameter("HOST");
int port = Integer.parseInt(getParameter ("PORT"));
client = new EmpClient (host , port);
try {
client.open();
} catch (Exception e) {
client = null;
}
}
public String initEmployee (String employee)
{
try {
client.initEmployeeRead(employee);
return null;
} catch (IOException e) {
return e.getMessage();
}
}
public String nextEmployee ()
{
try {
return client.readNextEmployee();
} catch (IOException e) {
return null;
}
}
public void destroy() {
try {
client.close();
} catch (IOException e) {
}
super.destroy();
}
}

 

[Andrew Thompson]

Hi,

Please refrain from multi-posting, as well as using
'cute' titles, in future.

(X-post to c.l.j.p./comp.os.vms, w/ f/u to c.l.j.p. only)

Andrew T.

 

[Lew]

Please refrain from multi-posting, as well as using
'cute' titles, in future.

(X-post to c.l.j.p./comp.os.vms, w/ f/u to c.l.j.p. only)

Andrew T.

Sorry to disagree, since most always I am with you on the Netiquette
reminders, but I recommend we not suppress 'cute' titles per se. However, to
the OP, if you give a hint as to the actual problem in the title that will
help you get better answers.

If you can do that and still be cute, more power to ye, but most likely you
will find that informative will preclude and trump cute.

- Lew

 

[Andrew Thompson]

...
Sorry to disagree,

No need for apologies..

...since most always I am with you on the Netiquette
reminders, but I recommend we not suppress 'cute' titles per se.

(shrugs) It is not a c.l.j.p. 'policy', nor even my
policy, as such. I would not mention it if that
was the only thing I had to say, but if I am
replying, I will mention it the way I did, and
leave it to the OP's initiative to follow it up..
(but yes, the reasons you mentioned are basically
why I advised against it)

Andrew T.

 

[Richard Maher]

Hi Oliver,

Thanks for your detailed reply, and your patience.

I can't imagine how HTML or the Java source code itself
might trigger this behaviour in your applet viewer program,

It ended up pilot error :-( I looked through the JAR manifest and to my
embarassment I found the EmpApplet and EmpClient classes but sadly no
EmpClient$Message class. Looks like a simple build error; sorry.

I am now getting the, equally lovely, "Incompatible magic value" error :-(
I'm guessing that it's because I'm running the latest and greatest 1.6 JDK
and the JVM on W2K won't work with that (I have run windows update; is there
a seperate JVM download site?) Anyway I have a 1.4.2 JDK on a Windows98 box
that I'll use to build the classes and the Jar and see if that makes a
difference.

I believe Roedy's site, mindprod.com, has a good overview of what to do
when you encounter a NoClassDefFoundError.
http://mindprod.com/jgloss/runerrormessages.html#NOCLASSDEFFOUNDERROR

Good pointer! I think I'll have need of that in the future :-(

I've never heard the term "Typing" before. Based on context, I'm
guessing you're referring to the *declaration* of "client" as being of type
EmpClient.

May be useful to think of my use of Java and OO terminology as analogous the
Policeman's French accent from the Television series 'allo 'allo. I'm
struggling but you get the general gist of what I'm talking about

In your code (which I've snipped), both classes are in the same package
(which happens to be the default, nameless package). Classes which are in
the same package don't need to import one another to be visible to one
another. Note that it's generally considered bad practice to use the default
package. Recommended practice is to put classes in a package whose name is
based on a domain name which you own (this is sort of to provide globally
unique package names). So if you own "google.com", you could call your
package "com.google.mypackage", for example.

Good tip! Taken on board.

Thanks again.

Cheers Richard Maher

 

[Oliver Wong]

I am now getting the, equally lovely, "Incompatible magic value" error :-(
I'm guessing that it's because I'm running the latest and greatest 1.6 JDK
and the JVM on W2K won't work with that (I have run windows update; is
there
a seperate JVM download site?) Anyway I have a 1.4.2 JDK on a Windows98
box
that I'll use to build the classes and the Jar and see if that makes a
difference.

Java 1.6 (AKA Java 6, Sun gives a lot of confusing aliases to their
version numbering system) just got officially released a few days ago (it
was previously in beta). You can download the JVM from
http://java.sun.com/javase/downloads/index.jsp

- Oliver

 

[Richard Maher]

Hi Oliver

Thanks for the reply.

Java 1.6 (AKA Java 6, Sun gives a lot of confusing aliases to their
version numbering system) just got officially released a few days ago (it
was previously in beta). You can download the JVM from
http://java.sun.com/javase/downloads/index.jsp

I downloaded that version and it certainly progressed things a bit but I'm
still floundering. I'm gonna be a bit contemptuous here and cut and paste a
request I sent to another bloke that's helping me, but if you could have a
quick glance over the versions at least (if nothing else) and let me know if
anything stands out (like the Object tag is dodgy) I'd really appreciate it!

Regards Richard Maher

I'm dying here!

I know you've held my hand and spoon fed me and if I can't tie my own shoe
laces by now then there's no help for me, but *please* look at what I have
done and tell me what I'm doing wrong!

This is Windows 2000 5.00.2195 SP 4 and iexplore 6.0.2800.1106 SUN JDK 1.6.0
(Latest Not beta)

Javac EmpClient.java
Javac EmpApplet.java

/* Maybe I should use the -g switch for debug info as I no longer seem to be
able to "stop at EmpApplet:1" in the Appletviewer anymore and the class and
archive files seem smaller. */

Jar -cf emp.jar EmpApplet.class EmpClient.class EmpClient$Message.class

Jar -tf emp.jar

// Looks good 3115 bytes for emp.jar

FTP to VMS box 1.2.3.6 type=image

$set file/attr=(rfm:udf) emp.jar

*NOW* If I use the <Applet> tag I get the classnotfound error and the reason
is "socket error unexpected end of file" but I have sent 3115 bytes with
your VMS COPY.

So I give up on the applet tag and move to the <OBJECT> tag but I can't find
a useful syntax diagram on the web and certainly not one with your
"verbs/attributes".

In your version you say "<object type=" but I can only find "codetype" in
the html specs and name="" and id="" simply do not exist and are replaced
with "param=".

This is what I'm left with: -

<html>
<head>
<script type="text/javascript">
function empchanged (txt)
{
var selectRef = document.forms[0]["users"];
var optsRef = selectRef.options;
while (optsRef.length > 0)
{
selectRef.remove(optsRef[0]);
}
var val = txt.value;
if (val.length > 0)
{
document.EmpApplet.initEmployee (txt.value);

for (;
{
var emp = document.EmpApplet.nextEmployee ();
if (emp == null)
break;
selectRef.add (new Option (emp,emp) , null);
}
}
}
function setemp (sel)
{
document.forms[0]["employee"].value = sel.options[sel.selectedIndex].value;
}
</script>
</head>
<body>
<form>

<object
width= "0" height= "0" >
<param name="type" value="application/x-java-applet;version=1.6.0">
<param name="archive" value="emp.jar">
<param name="code" value="EmpApplet.class">
<param name="codebase" value="http://1.2.3.6/">
<param name="mayscript" value="yes">
<param name="scriptable" value="true">
<param name="name" value="EmpApplet">
<param name="HOST" value="1.2.3.6">
<param name="PORT" value="3333">
</object>


<input type="text" name="employee" onchange="empchanged (this);"
onkeyup="empchanged (this);">
<select name="users" onchange="setemp(this);"></select>
</form>
</body>
</html>


This code works with the AppletViewer and connects to my VMS name-lookup
server (Which also proves that your mickey-mouse applet uploader is doing
it's job) but won't work with the html as I get (depending on which html
page I try) document.EmpApplet is null or not an object OR Object does not
support this property or method AT
document.EmpApplet.initEmployee(txt.value)

I *have* copied the latest and greatest Frames example and I get "null is
null or not an object" at test.html aka "parent.frames.appletframe.document
is null or not an object"

I come to you cap in hand in all humility knowing full well that I am not
paying you for this and you have much work to do but *FOR PETE'S SAKE* if
this is how hard it is to get a "simple" applet working then no wonder
everyone isn't doing it :-(

Please, please, please no frames, missionary position only code that I can
compile and run on W2K. There is every possibility that I am an idiot and
everyone else can do this, but on the other hand I submit to you that your
code will simply not *compile* and run on W2K.

Who cares? You might say; we are *nix biggots and don't care about that blah
blah blah, but have a heart will ya? I did give the casual observer a DCL
command file that could be just (AT)ed. I'm not asking for that but just
change your /test/ to a remote VMS connection or tell me "You're a dickhead
and everyone knows that your dickie$path environmental variable must be
pointing to /test/ for frame.html to pick up test and test1"

 

[Oliver Wong]

[...]

This is what I'm left with: -

<html>
<head>
<script type="text/javascript">
function empchanged (txt)
{
var selectRef = document.forms[0]["users"];
var optsRef = selectRef.options;
while (optsRef.length > 0)
{
selectRef.remove(optsRef[0]);
}
var val = txt.value;
if (val.length > 0)
{
document.EmpApplet.initEmployee (txt.value);

for (;
{
var emp = document.EmpApplet.nextEmployee ();
if (emp == null)
break;
selectRef.add (new Option (emp,emp) , null);
}
}
}
function setemp (sel)
{
document.forms[0]["employee"].value =
sel.options[sel.selectedIndex].value;
}
</script>
</head>
<body>
<form>

<object
width= "0" height= "0" >
<param name="type" value="application/x-java-applet;version=1.6.0">
<param name="archive" value="emp.jar">
<param name="code" value="EmpApplet.class">
<param name="codebase" value="http://1.2.3.6/">
<param name="mayscript" value="yes">
<param name="scriptable" value="true">
<param name="name" value="EmpApplet">
<param name="HOST" value="1.2.3.6">
<param name="PORT" value="3333">
</object>


<input type="text" name="employee" onchange="empchanged (this);"
onkeyup="empchanged (this);">
<select name="users" onchange="setemp(this);"></select>
</form>
</body>
</html>


This code works with the AppletViewer and connects to my VMS name-lookup
server (Which also proves that your mickey-mouse applet uploader is doing
it's job) but won't work with the html as I get (depending on which html
page I try) document.EmpApplet is null or not an object OR Object does not
support this property or method AT
document.EmpApplet.initEmployee(txt.value)

It sounds like your problem has to do with getting JavaScript to talk to
your Java applet, a topic on which I know almost nothing about. If nobody
else answers here, perhaps you can crosspost the above (the FTP stuff, etc.
does not seem relevant to me) to the JavaScript and Java newsgroup, in a new
thread, with a subject line which summarizes the problem like "How to get
JavaScript to talk to my Java applet" or something similar.

- Oliver

 

[Oliver Wong]

perhaps you can crosspost the above (the FTP stuff, etc. does not seem
relevant to me) to the JavaScript and Java newsgroup

And in case you don't know how to crosspost, see
http://www.cs.tut.fi/~jkorpela/usenet/xpost.html

- Oliver

 

[Richard Maher]

Hi Oliver,

Thanks for the pointers, and you could well be right about it being a
Javascript calling Java issue, but before I shoot off over there let me
provide a little more info here in case it rings a bell with someone.

My JAR file is as follows:
Directory of C:\Java\Bojan\Applets

17/12/2006 08:27p 3,115 emp.jar
1 File(s) 3,115 bytes

C:\Java\Bojan\Applets>jar -tf emp.jar
META-INF/
META-INF/MANIFEST.MF
EmpApplet.class
EmpClient.class
EmpClient$Message.class

Here's the Applet.html:
<html>
<body>
<form>
<applet name="EmpApplet"
id="EmpApplet"
code="EmpApplet.class"
archive="emp.jar"
codebase="http://1.2.3.6/"
width="40"
height="40">
<param name="HOST" value="1.2.3.6">
<param name="PORT" value="3333">
</applet>
</form>
</body>
</html>

NB; I Have used a <object> tag version with exactly the same results.

If I invoke that Applet with the 1.6 AppletViewer then it fires up and does
what it should. If I use IE to fireup Applet.html I get:
java.lang.ClassNotFoundException: EmpApplet.class
at sun.applet.AppletClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.applet.AppletClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.applet.AppletClassLoader.loadCode(Unknown Source)
at sun.applet.AppletPanel.createApplet(Unknown Source)
at sun.plugin.AppletViewer.createApplet(Unknown Source)
at sun.applet.AppletPanel.runLoader(Unknown Source)
at sun.applet.AppletPanel.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

Caused by: java.net.SocketException: Unexpected end of file from server

at sun.net.www.http.HttpClient.parseHTTPHeader(Unknown Source)
at sun.net.www.http.HttpClient.parseHTTP(Unknown Source)
at sun.net.www.http.HttpClient.parseHTTPHeader(Unknown Source)
at sun.net.www.http.HttpClient.parseHTTP(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown
Source)
at java.net.HttpURLConnection.getResponseCode(Unknown Source)
at sun.applet.AppletClassLoader.getBytes(Unknown Source)
at sun.applet.AppletClassLoader.access$100(Unknown Source)
at sun.applet.AppletClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
.... 10 more

So has IE misinterpreted some bytes as a premature End-of-File? (All 3115
were sent)?
Using ("Content-Type: application/octet-stream!/")

Is it a compatibility issue and IE can't see a JDK-1.6-generated
EmpApplet.class header in the JAR file?

Should I deinstall the JDK and reinstall 1.5 (or something?)

Can I use the -target switch on JAVAC?

Would -debug help?

How about JAR -e EmpApplet?

Anything?

Regards Richard Maher

PS. Looks simple huh?

 

[Oliver Wong]

If I invoke that Applet with the 1.6 AppletViewer then it fires up and
does
what it should. If I use IE to fireup Applet.html I get:
java.lang.ClassNotFoundException: EmpApplet.class

Perhaps you have the MSJVM installed instead of (or in addition to)
Sun's JVM. See http://www.mvps.org/marksxp/WindowsXP/java.php

Unless you have some special reason for supporting the MSJVM, you should
probably remove it in favour of Sun's.

- Oliver

 

[Andrew Thompson]

Please refrain from multi-posting, as well as using
'cute' titles, in future.

The following is crudely requoted from a strand
to this thread on which I have no intention of
directly replying.

The (current) problem can be explained by the
following four lines..

codebase="http://1.2.3.6/"
....AppletViewer then it fires up and does what it should.
If I use IE to fireup Applet.html I get:
....
at java.security.AccessController.doPrivileged(Native Method)

And, since you have not replied to it thus far, I will
repeat.. Please refrain from multi-posting, as well
as using 'cute' titles, in future.

Andrew T.

 

[Richard Maher]

Hi Oliver,

Thanks again for the replies.

Unless you have some special reason for supporting the MSJVM, you should
probably remove it in favour of Sun's.

All I want to do (with no specific application in mind) is be able to show
anyone, who asks me, how to use html, Javascript, and Java Applets to
connect back to an application server using TCP/IP Sockets. While your
recommendation to use the Sun JVM is probably a good one in, that it removes
at least one more variable, I do not wish to make it a requirement.

I'm guessing that the answer to particular my problem lies in some trivial
environmental setting; but which one?

The ability to Connect() back to the server where the Codebase and Archive
files live *without having to run with specially elevated privileges* is
functionality that I find extremely appealing! Now if I could just get it to
work. . . :-(

Cheers Richard Maher

 

[Richard Maher]

Hi Andrew,

The (current) problem can be explained by the
following four lines..

codebase="http://1.2.3.6/"
...AppletViewer then it fires up and does what it should.
If I use IE to fireup Applet.html I get:
...
at java.security.AccessController.doPrivileged(Native Method)

I have no idea what motivates you to respond the way you do, nor do I
particularly care, If that's how you get your jollies then good for you. But
I'm guessing that the above was a genuine attempt at assistance, and
possibly the answer and I'm just too thick to see it.

If so, could you please show me what those four lines "explain" about
getting unexpected eof on the socket to the codebase?

The "GET" has gone to the codebase and has been (AppletViewer thinks so
anyway) satisfied. I see no SSL request, I see no certificate or signature
request, The JAR contains EmpApplet and all 3115 bytes have been sent. I
looked up doPrivileged and it looked like it was asking for elevated
privileges, is that the problem?

Just think, if I get all these problems sorted then there's a good chance
that I'll leave this newsgroup for good! One less irksome poster? That's
gotta be *all* gravy.

Regards Richard Maher

BTW. Has anyone actually seen Andrew's CLJP Sheriff's badge? When are the
next elections held?

 

[Richard Maher]

Hi All,

Rather than a Java programmer problem, this ended up a "Writing a WebServer
101" problem :-(

Although, I had told Interenet Explorer that I only speak "http 1.0" I had
stuck a loop on my "read" of the GET command just to check that something
else may have come down the line. The problem appears to be that IE seems to
want a Socket Disconnect status (at least http 1.0) to tell it that EOF has
occured even though I told it that 3115 bytes were coming and I had already
sent 3115 bytes.

I took out the loop and shutdown the socket immediately after the JAR file
was sent, and IE was happy!

Well, sort of; did you know that IE asks me *3* times for the same Archive
file (looks like once per class) even though all of the classes are in the
one JAR file *and* in the manifest. Any ideas why this is so? Have I missed
a switch on the JAR creation of on the Applet declaration? Here's the latest
applet def: -

<html>
<body>
<form>
<object classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
width= "40" height= "40" name="EmpApplet"
id="EmpApplet">
<param name="archive" value="emp.jar">
<param name="codebase"
value=http://1.2.3.6/>
<param name="code" value="EmpApplet">
<param name="mayscript" value="yes">
<param name="scriptable" value="true">
<param name="name" value="EmpApplet">
<param name="HOST" value="1.2.3.6">
<param name="PORT" value="3333">
</object>
</form>
</body>
</html>

Anyway, Merry Christmas to one and all, and I might even stretch to a real
Java coding question next year

Cheers Richard Maher