JNLP Example


Continuing the JNLP part

Let’s create an HelloWorld in jnlp, i.e. an `file.jnlp` that when opened, shows Hello world:

Creating a java swing/awt class:

//Based totally in http://www.mkyong.com :D I hope he allows me
public class TestJnlp {
  static BasicService basicService = null;
  public static void main(String args[]) {
    JFrame frame = new JFrame("Example JNLP");
    JLabel label = new JLabel();
    Container content = frame.getContentPane();
    content.add(label, BorderLayout.CENTER);
    String message = "Yo Gabriel";


    try {
      basicService = (BasicService)
    } catch (UnavailableServiceException e) {
      System.err.println("Lookup failed: " + e);

    JButton button = new JButton("Button");

    ActionListener listener = new ActionListener() {
      public void actionPerformed(ActionEvent actionEvent) {
        try {
          URL url = new URL(actionEvent.getActionCommand());
        } catch (MalformedURLException ignored) {


    content.add(button, BorderLayout.SOUTH);

To compile, don’t forget to add `jnlp.jar` in the classpath,


Create a jar with the file: jar -cf TestJnlp.jar TestJnlp.* And sign the jar with your keystore:

[fdemeloj@fdemeloj JNLP]$ jarsigner -keystore eap7console.jks TestJnlp.jar alias

Don’t forget to consult the JAVAWS syntax.


Just do javaws Test.jnlp:


For troubleshooting, I would suggest Developer Guide JavaWS

The issues you can find:

1. Wrong location

net.sourceforge.jnlp.LaunchException: Fatal: Read Error: Could not read or parse the JNLP file. You can try to download this file manually and send it as bug report to IcedTea-Web team.
	at net.sourceforge.jnlp.Launcher.fromUrl(Launcher.java:487)
	at net.sourceforge.jnlp.Launcher.launch(Launcher.java:287)

2. JAR not signed

Caused by: net.sourceforge.jnlp.LaunchException: Fatal: Application Error: Cannot grant permissions to unsigned jars. Application requested security permissions, but jars are not signed.
	at net.sourceforge.jnlp.runtime.JNLPClassLoader$SecurityDelegateImpl.getClassLoaderSecurity(JNLPClassLoader.java:2481)
	at net.sourceforge.jnlp.runtime.JNLPClassLoader.setSecurity(JNLPClassLoader.java:385)

3. Main-class

Caused by: net.sourceforge.jnlp.LaunchException: Fatal: Initialization Error: Unknown Main-Class. Could not determine the main class for this application.
	at net.sourceforge.jnlp.runtime.JNLPClassLoader.initializeResources(JNLPClassLoader.java:774)
	at net.sourceforge.jnlp.runtime.JNLPClassLoader.<init>(JNLPClassLoader.java:338)
	at net.sourceforge.jnlp.runtime.JNLPClassLoader.createInstance(JNLPClassLoader.java:421)

Don’t try to execute as jar, this will return to you:

[fdemeloj@fdemeloj test_jnlp]$ java -jar TestJnlp.jar 
Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.NoClassDefFoundError: javax/jnlp/UnavailableServiceException
	at java.lang.Class.getDeclaredMethods0(Native Method)
	at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
	at java.lang.Class.privateGetMethodRecursive(Class.java:3048)

At the end of the day, javaws -help is a friend

To debug:

export JAVAWS_VM_ARGS="-verbose -J-Xdebug -J-Xnoagent -J-Xrunjdwp:transport=dt_socket,address=8787,server=y,suspend=y -Xnofork"

javaws Test.jnlp $JAVAWS_VM_ARGS #this starts Iced Tea Web

But this is for the third part of this series …

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