NetBeans – Remote Java ARM debugging with GUI

There is a known issue related to NetBeans remote debugging a Java application with GUI enabled (Swing/JavaFX) running on embedded Linux (Raspberry Pi, BeagleBone Black etc.).

Photo from – https://www.ematador.pl/

When one tries to run / debug an application with GUI components then java.awt.HeadlessException with “No X11 DISPLAY variable was set, but this program performed an operation which requires it” message is being thrown.

Long story short, the DISPLAY environment variable is empty and remotely run program does not know the display it is supposed to appear on – hence the error.

For my setup the problem was solved by small modification to ANT build XML script. I have found the “-copy-to-remote-platform” target, copied it to notepad++ and slightly modified it by adding highlighted lines.

Then I have pasted modified ANT target to build.xml file of my project to override the target (you can not just edit …-impl.xml file because your changes will be lost after each NetBeans restart or configuration changes).

Voila! Now I can run and debug my application remotely with GUI displayed on my BeagleBone Black 7” LCD display – pretty neat. One could modify my code to point a remote X server (like Xming) as a display.

<!-- Remote ARM linux deploy overwrite !-->
    <target name="-copy-to-remote-platform">
      <macrodef name="runwithpasswd" uri="http://www.netbeans.org/ns/j2se-project/remote-platform/1">
            <attribute name="additionaljvmargs" default=""/>
            <sequential>
                <sshexec host="${remote.platform.host}" port="${remote.platform.port}" username="${remote.platform.user}" password="${remote.platform.password}" trust="true" command="mkdir -p '${remote.dist.dir}'"/>
                <scp todir="${remote.platform.user}@${remote.platform.host}:${remote.dist.dir}" port="${remote.platform.port}" password="${remote.platform.password}" trust="true">
                    <fileset dir="${dist.dir}"/>
                </scp>
                <antcall target="profile-rp-calibrate-passwd"/>
                <sshexec host="${remote.platform.host}" port="${remote.platform.port}" username="${remote.platform.user}" password="${remote.platform.password}" trust="true" usepty="true"
                    command="export DISPLAY=:0; cd '${remote.project.dir}'; ${remote.platform.exec.prefix}'${remote.java.executable}' @{additionaljvmargs} -Dfile.encoding=${runtime.encoding} ${run.jvmargs} ${run.jvmargs.ide} -jar ${remote.dist.jar} ${application.args}"/>
            </sequential>
        </macrodef>
        <macrodef name="runwithkey" uri="http://www.netbeans.org/ns/j2se-project/remote-platform/1">
            <attribute name="additionaljvmargs" default=""/>
            <sequential>
                <fail unless="remote.platform.keyfile">Must set remote.platform.keyfile</fail>
                <sshexec host="${remote.platform.host}" port="${remote.platform.port}" username="${remote.platform.user}" keyfile="${remote.platform.keyfile}" passphrase="${remote.platform.passphrase}" trust="true" command="mkdir -p '${remote.dist.dir}'"/>
                <scp todir="${remote.platform.user}@${remote.platform.host}:${remote.dist.dir}" port="${remote.platform.port}" keyfile="${remote.platform.keyfile}" passphrase="${remote.platform.passphrase}" trust="true">
                    <fileset dir="${dist.dir}"/>
                </scp>
                <antcall target="profile-rp-calibrate-key"/>
                <sshexec host="${remote.platform.host}" port="${remote.platform.port}" username="${remote.platform.user}" keyfile="${remote.platform.keyfile}" passphrase="${remote.platform.passphrase}" trust="true" usepty="true"
                    command="export DISPLAY=:0; cd '${remote.project.dir}'; ${remote.platform.exec.prefix}'${remote.java.executable}' @{additionaljvmargs} -Dfile.encoding=${runtime.encoding} ${run.jvmargs} ${run.jvmargs.ide} -jar ${remote.dist.jar} ${application.args}"/>
            </sequential>
        </macrodef>
    </target>