We are required to add export DISPLAY=:0.0 in tomcat's startup file and batch server's startup file. This is to make java see the X11 Display libraries on Unix and run our applet. Without this export in the startup files, the applet throws a Headless Exception.
Though this explicit export makes the java applet run, it disrupts the other applications running on the server. Is there a way where I can make this export DISPLAY=:0.0 run from within java code instead of adding it to startup files? And if it is possible, would that be a good approach?
I have already tried setting the system property to -Djava.awt.headless=true , but it didn't work. As the link given above http://java.sun.com/developer/technicalArticles/J2SE/Desktop/headless/ also says that setting headless=true would work only for few components like Canvas, Panel but it will not work for the top level components.
So I feel the only option left for me is using export DISPLAY=:0.0. This is making my applet work when set in the startup files but causes problem for other applications running in the server. So if anybody could help me to make export DISPLAY=:0.0 work such that it doesn't interfere with other applications in the server. One way I thought was to export the display through code.
Any help would be highly appreciated.
I believe you can actually set the system property -Djava.awt.headless=true which will allow access to the graphic libraries without actually needing a display.
See http://java.sun.com/developer/technicalArticles/J2SE/Desktop/headless/ for more info.
From your question it seems that there is something seriously wrong with your configuration.
Tomcat should always be able to run server-side without a display.
Applets always run in browser and get the x11 environment from the browser. The applet's jar could be served by tomcat, or apache, or something else, but that's irrelevant.
If your applets communicate with the server, make sure that the server code is completely separate from your applet code (keep them in separate projects) and that it doesn't use any awt code. If it does (for image manipulation, etc.), then use -Djava.awt.headless as jdewald said.
How is this affecting other applications? How are you defining the environment variable in your start up scripts? If you're defining the variable correctly, it should only affect programs started by your start up script, i.e., Tomcat and the batch server.
Also, your original question doesn't really add up. Are you running both the server and client (Tomcat and the web browser) on the same machine?
Related
I have been using IntelliJ for a while now and I'm enjoying its suite of features but I'm having a hard time getting the run configurations to work for a java applet. I have a pre-existing Java tool that uses Swing and I'm using the JApplet class to load those GUI objects as an applet. The problem is I have a couple configuration files that I need loaded. I load these from the working directory and from my knowledge, this working directory would normally be the directory in which the applet resides. I think the major problem is IDEA sets the startup variable:
-Didea.launcher.bin.path=IDEA_BIN_DIR
I would like to be able to change this but I am seemingly unable to. I have tried overriding this flag by editing the applets run configuration VM parameters, but IDEA will continue putting the above one in even if I specify something different.
So in short, I'm having a hard time loading a local configuration file because I can't set the working directory for the run configuration in IDEA. Does anyone know how to get around this or know of a better way of running Java applets that use configuration files, in IDEA?
An applet normally runs in a sandbox in a browser, and such an applet can't access the local computer's file system, for security reasons.
Thus it is generally a bad idea to load configuration files from the file system, and "working directory" is not a useful term for an applet.
If these files change seldom (i.e. in principle only by the developer), you can put them to the applet's class files (i.e. in the jar file, or during development in the directory where the classes will be generated), and use class.getResource() or .getResourceAsStream() to load them.
If the configuration files should be definable by the webmaster, put them on the webserver - either at some fixed location relative to getCodeBase() or .getDocumentBase(), or specify them as parameters to your applet tag in the HTML tag.
If these are user specific configuration files (which the applet should be able to write), you either need to store them on the server and retrieve/store after a login (i.e. you need some logic at the server side), or you would store them at the client side.
The current way to do this would be using the JNLP API (in javax.jnlp.*) - there are some interfaces allowing Persistence, or loading/storing data (with the user having a FileChooser). Alternatively, you could sign your applet and request an AllPermission from the user - then you can access the file system.
Sorry, nothing of these answers your original question (I don't use IDEA), but maybe these help you to find another way.
I have written a server in Java that allows clients connected to it to control the mouse and keyboard of the computer. To do this it uses the java.awt.Robot class.
I need this server to run in the background and start automatically. The first OS I am tackling this problem on is Debian based (Ubuntu 11.04) and a daemon seems like the obvious choice. The problem is that when the daemon is started during boot or during the installation of my debian package (whose postinst script starts it using /etc/init.d/pc-remote-server start) I get this error:
java.awt.AWTException: headless environment
at java.awt.Robot.<init>(Robot.java:97)
at com.se.pcremote.server.CommandExecuter.<init>(CommandExecuter.java:72)
at com.se.pcremote.server.PCRemoteServer.<init>(PCRemoteServer.java:215)
at com.se.pcremote.server.PCRemoteServer.main(PCRemoteServer.java:122)
Is there any way I can use the java.awt.Robot class from within a daemon process? Could I spawn a secondary process from the daemon process that is not a 'headless environment'? Or is there a better way for me to get a 'service' like result that does not have this limitation?
"Headless" means that this code needs access to a graphics environment, and it hasn't.
You can run in headless mode by supplying a system property which provides a crude implementation which gives just the basics for running applications, but which most likely cannot support Robot. Try it however first.
If you cannot do that, you need a graphics environment for your process. The usual way to do this is to run a VNC X-server as it doesn't require physical hardware, and then connect to it.
I assume, you must set the DISPLAY variable correctly (in the environment of the robot process at the time when the robot process is started) for this to work -- in your case you would need to specify a display in your DISPLAY variable which is created some time after the program is started. --
No idea whether this really works, but you could give it a try and report back here whether it works.
Alright, after doing some more research and trying some more options here is what I came up with:
Can I use java.awt.Robot from within a daemon? No.
Further down in my question I elaborated a little:
Is there any way I can use the java.awt.Robot class from within a daemon process? No. As above.
Could I spawn a secondary process from the daemon process that is not a 'headless environment'? Not that I could figure out. It was going to be a lot of work if I did do it anyway.
Or is there a better way for me to get a 'service' like result that does not have this limitation? Yes! Use the desktop environment! In my case since I was using Ubuntu the desktop environment was Gnome. Gnome has a Startup Applications feature that runs off .desktop files on a global and per-user basis as described here. They also provide information on the structure of these .desktop files here. I added a .desktop file to /etc/xdg/autostart (the global autostart folder) that ran my Java 'service' and it worked like a treat.
I want to facilate my client to run java program through UNIX command prompt using some shells. It'll look more effecient if they would be able to give input through some GUI. So it can be tested immedietely. I dont want prefer unix commands fro input.
Can somebody tell me how to run Java swing or applet programs in UNIX?
As Thompson mentioned, looking at Java Web Start could be a good idea.
Otherwise, if what you want is to execute, using a *NIX-like terminal, an application located on a remote host and have it rendered on your local display, then you need to do a few things:
you need a working X server on the local machine
you need to export the DISPLAY to the local machine (you can do this by setting up the DISPLAY environment variable on the remote system)
then you need to start your Java app from the command-line.
Hope this helps.
Here's an example of how to export your display over SSH.
Java programs use the X windows system (just like any other GUI on Unix). Assuming your X windows system is setup correctly, you should just open up a JFrame and do your GUI coding just like Windows.
Using the command prompt to launch a GUI is so last millennium. If you can distribute from a server, look into Java Web Start to provide the end-user with a simple and painless install.
Oh, and of course, follow Starkey's advice to throw a JFrame into the mix.
If you have an X-server installed locally, Putty can tunnel the X11-graphics generated by Linux Java back from the server to your local machine, and view it there.
If the above doesn't make sense to you, your next best bet is either running the Java code locally with Java Web Start (and code it to communicate back to the remote server) or run Servlets inside a Java Web Server running on the remote host.
In other words, GUI over a Putty connection is not something which is easily done.
I have a Java program using AWT which I would like to run on a headless system. The display for the program does nothing other than display stats. When the program finishes, it exits. There is no user interaction on the display. The program creates an output file which I use in my build system.
Is there a way to get the Java program to run without an X11 display configured? Can I force Java to run the program without trying to display anything? I do not have access to the source code (it is just .jar file), so I can't make modifications to the source.
Any thoughts on how I could get this to work?
The underlying question here is how to run Java applications without an X server; providing a "fake" X server is only one option. In Java 1.4 and up, you can do the following:
java -Djava.awt.headless=true
This allows applications which use AWT to run on headless systems even without an X server.
Xvfb can do what you ask for. I've not used it myself, but here is a link to wikipedia: http://en.wikipedia.org/wiki/Xvfb
You can use a vncserver.
vncserver :1001
export DISPLAY=localhost:1001
java..
The added advantages is that you can actually view the gui
using vncserver 'just in case'
Could also run Xvnc in a low resolution and color depth.
As mentioned by Charles Duffy the traditional method is to tell Java to go headless.
Note that you can always mount the jar in Eclipse and use jad+jadclipse to see what it actually does, and perhaps even override a class if you need to by putting another class-file in "front" of it in the classpath.
A facility that might be relevant if the program uses Java2D is that newer Java versions use optimizations in the X11 server to render faster. This alone might be a reason to devote an X11 server attached to a high performance graphics card to your graphics processing.
I've used with great success in the past the PJA libraries, they don't seem to be maintained anymore, but then again, just just want to run...
I was able to get headless mode in OpenJFX with the command line arguments
-Dglass.platform=Monocle -Dmonocle.platform=Headless -Dprism.order=sw
I am using Tomcat 5.5.23, JDK 1.5 on HP Unix. We have an application which when invoked form tomcat starts an applet. It was working fine till JDK 1.4. But now we have moved to JDK 1.5 and the applet does not start. The exception thrown is -
java.awt.HeadlessException:
No X11 DISPLAY variable was set, but this program performed an operation which requires it.
I then added JAVA_OPTS="-Djava.awt.headless=true" to catalina.sh file. But still I get the same Headless exception, but this time without the X11 Display message.
Any help would be appreciated.
Odd.. you're trying to run an applet (I assume you are talking about a subclass of java.awt.Applet) inside tomcat? Generally this won't work because there's no display on which to display the applet.
Assuming you don't want the applet to display anywhere and you just want to execute some portion of it programmatically, you may be able to get by using a virtual X server such as Xvfb or Xvnc. Once you have Xvfb or Xvnc running on your host running tomcat, you might try to set the DISPLAY inside the tomcat startup scripts to use the display of the virtual X server.
-Djava.awt.headless=false
add above in your Tomcat startup script. it will work 100%
You are maybe using something in your Java code that can not work on a headless system, such as graphics components (Swing objects, images, etc.). Some of these components, instead of being directly handled by Java, are handled by underlying platform (Windows kernel itself or X-Window server on Unix). This way the overall performance of application is boosted.
So the question now is, ok if it was working on Java 1.4, why doesn't it work on 1.5? My bet, given the peformance boost since Java 1.2 that Swing has received over time, is that Sun has moved the management of some graphic objets to OS level to increase performance. So if you can not stick to 1.4, then you should revise your code.
This good article will help you understand how to modify your application to make it headless-friendly.
Applets are going to have a hard-time running server-side. They are designed to run inside of a container, such as a web browser. The exception is getting thrown most likely because the applet is trying to draw it's GUI -- and the server is providing no support for this. I'm surprised that it worked in JDK 1.4 -- I don't know what changed between the two revisions which would have affected this.
You may also have to install the x11 libraries, or at least explicitly export the path to them.
/usr/X11R6/lib
Open $CATALINA_HOME/bin/startup.sh file with your preferred text browser
Paste this line export CATALINA_OPTS="$CATALINA_OPTS -Djava.awt.headless=false" at the beginning of the file
Save and close the file
Restart Tomcat
In spring boot with database access, when you specify asterisks: **** as username and password, it will try to prompt the user for a username and password (you read that right), and it will throw this HeadlessException if it's not a gui application.