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Java logging in client application

I've made a small desktop application in java for OS X. I've packaged in into a .app using JarBundler. Everything runs fine on my computer.
When I send the .app to someone else (also running a mac), the app opens and closes immediately. Is there a log file of some kind I can get from their computer (which I have full access to). Is there a way to get System.out.println statements or similar to show up in that file?

execute the application from the console, from there any errors will be printed to the standard error stream.

Please avoid using System.out.println() statements on the application. The method is synchronized and results in poor performance. Not to mention you may not be able to retrieve the statements based on who captures the console.
Use a logging solution like sl4j and back it up with a logger like log4j with a file appender. The file appender writes to a file and you can get your debug statements / stack traces from there.

Java app startup with computer and be able to see system.out.println?

I wrote a simple Java app which I have placed in the start up folder of my programs which makes the program starts when the computer starts up. what is the easiest way to make it open a command line or something which I can see the System.out.println results instead of just running in the background?

You should familiarize yourself with logging frameworks such as logback and log4j. Instead of using System.out.println you use some special API and the logging library redirects all messages to preconfigured appenders like console or file.
In your case you can configure your application to log on console while developing and switch to file when configuring an application to run from startup.
This won't really open a new command line window on startup, but instead it will store all messages to some predefined file on disk - which is actually even better.

You can use Log4j API for logging the details with the predefined outputs. It is far better then using SOP. Because it is light waighted and also very simple to configure the logs in the other files with the output format whichever you want to make.
http://logging.apache.org/log4j/1.2/ Go to this url where you can find log4j api available.
Hope this work for you
Enjoy !!!

Untraceable exception in java applet

I'm having some problems tracing the reason that I can't load a java(fx) applet.
The java plugin console for the browser has always been my sole source of information for problem solving. The reason it isn't much help at the moment is that the applet starts to load, downloading the jar files and outputting a percentage to the console along with the occasional statement to say it's on the next jar file. At some point in time (different percentages each time) the console just closes unexpectedly and the applet stops loading. I know this isn't much to go on but I was wondering if there was any way that the output from the console could be stored to a file on the local machine. To debug this particular problem, changing security permissions temporarily would be acceptable.
The problem has occured on every pc i've tried, however if I keep refreshing after failure it seems to cache the jar files previously downloaded and thus get further through the loading process until it eventually works. My issue now is that on a particular customers network refreshing does not resolve the issue. I thought it may be a permissions issue writing to disk but I've tried an administrator account and still no luck. I've also tried a variety of browsers. It might also be worth noting that they go through a proxy server - when the applet tries to load it asks for the credentials for logging on to the proxy which seems to authorise fine.
If anyone has a suggestion on what I could try it would be gratefully received.
Thanks,
James

Two points:
You should be able to get a stack trace through the applet console viewer (which runs in the system tray on PC's) and if you open that up it will show you your stack trace for debugging.
Can you reproduce this problem using the Java Applet Viewer tool? This will allow you to write unit tests, and debug much more easily.

I forget where it is, but somewhere in the java control panel (one of the options under the advanced tab I believe) there's an option to turn on logging. This will log all output to the java console to a file as well. I've used this when trying to debug issues similar to this.
There's some info here on where the files will appear:
http://download.oracle.com/javase/1.5.0/docs/guide/deployment/deployment-guide/tracing_logging.html

The problem ended up being some JS code that was making calls to the applet before the applet had initialised.

How to debug/log/trace an applet loading problem?

Recently two of our clients have reported problems with our applets. Looking at the java plugin console it is full of ClassNotFoundException so none of our code is executed.
I've been able to reproduce the stack trace using a virtual pc image with 0 free space on disk, but the problem goes away as I restore some disk space, and the users tell me that their disk is not full; they are able to create new files.
Our applet requires java 6, and the problem has appeared with updates 1, 10 and 14 of the jre. We have also tried different browsers (IE and Firefox), clearing the browser and java caches, ...
How can I debug or trace what is the jvm doing to load our applet?
I suppose that the problem lies on some security directive on windows so I'm using Sysinternal's Process Monitor to log the activity but I don't really know where to look at.

The Java cache is most likely messed up. Open Java in the Control Panel and get rid of all temporary files to see if it goes away.
Logging in the Java Console for loading applets can be enabled which helps quite alot (even if the plugin is extremely cryptic). See http://java.sun.com/javase/6/docs/technotes/guides/deployment/deployment-guide/tracing_logging.html

I've been looking at the plugin source from the JDK and I've found that there is additional debug info available in the logs setting the environment variable JPI_PLUGIN2_DEBUG.
Unfortunately I still only see ClassNotFound exceptions.
I've found a piece of the plugin code that swallows all exceptions, so maybe my users problem is there...

had similar problems a while ago. In our case, the problem seems to be how the applet tag is set up on the web page. If it is in a wrong order or contains the codebase attribute, it fails with 6u10+. This works for us:
<applet name="DMGANTT" archive="DMGantt.zip" code="dm.applet.DMGanttApplet"
width='100%' height='100%' mayscript="mayscript">

We had a similar problem with one of our clients. We discovered that it was a strange bug in some versions of Java related to proxy configuration on the client. See this article for the details
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6723715
Also, our applet failed with new versions for a different reason.
Now, in similar cases I ask them to check javatester.org, so that I can see if applets (in general) load OK in their browser. If that page loads OK, its a problem on our applet (or page). Else it's a problem in their configuration. I help them anyway but it's easier to debug.

How do I pipe the Java console output to a file?

I found a bug in an application that completely freezes the JVM. The produced stacktrace would provide valuable information for the developers and I would like to retrieve it from the Java console. When the JVM crashes, the console is frozen and I cannot copy the contained text anymore.
Is there way to pipe the Java console directly to a file or some other means of accessing the console output of a Java application?
Update: I forgot to mention, without changing the code. I am a manual tester.
Update 2: This is under Windows XP and it's actually a web start application. Piping the output of javaws jnlp-url does not work (empty file).

Actually one can activate tracing in the Java Control Panel. This will pipe anything that ends up in the Java console in a tracing file.
The log files will end up in:
<user.home>/.java/deployment/log on Unix/Linux
<User Application Data Folder>\Sun\Java\Deployment\log on Windows
/~/Library/Caches/Java/log on OS X

(If you can modify the code) you can set the System.out field to a different value:
System.setOut(new PrintStream(new FileOutputStream(fileName)));
If you are running a script (invoking the program via java) from Unix you could do:
/path/to/script.sh >& path/to/output.log

In Mac 10.8.2 logs could be found at /Users/<userName>/Library/Application Support/Oracle/Java/Deployment/log/.
Before you have to enable logging from Java Control Panel. Option "Enable logging" is at tab "Advanced". Java Control Panel could be started from "System preferences".

A frozen console probably means a deadlock (it could also mean repeated throwing of an exception). You can get a stack dump using jstack. jps may make finding the process easier.

try this guide it works for me. it also guides you that how you can set "System.setOut(fileStream);", "System.setErr(fileStream);"