Import *.jar File in Java Code

[ManChun Lam]

The following is a simple SWT HelloWorld code,

/*
 * SWTHelloWorld
 *
 * A dialog box with the title "Hello World"
 */
import org.eclipse.swt.widgets.*;
import org.eclipse.swt.*;
 
public class SWTHelloWorld
{
    public static void main(String[] args)
    {
        Display display = new Display();
        Shell shell = new Shell(display);
        Label label = new Label(shell, SWT.NONE);
        label.setText("Hello, World!");
        shell.pack();
        label.pack();
        shell.open();
        while (!shell.isDisposed())
        {
            if (!display.readAndDispatch())
            {
                display.sleep();
            }
        }
        display.close();
        label.dispose();
 
    }
 
}

It works well in Eclipse, since I can set the project to reference the jar "swt.jar".

Let's say I want to deploy this, do I have to extract everything inside "swt.jar", then re-jar those files with SWTHelloWorld.java? Or can I just say something like "import swt.jar", and use everything inside it.

Thank you for all your help.
[ August 07, 2008: Message edited by: ManChun Lam ]

[Rob Spoor]

When you create a JAR file with your own application, you can specify the classpath:

Class-Path: swt.jar

This path is relative to your own JAR file, so with that example you should just put the swt.jar file in the same folder as your JAR file. You can also choose to use subfolders.

Note that you should NOT put swt.jar INSIDE your JAR file, because then you will have to use some workarounds which are, in my opinion, not worth it.

[ManChun Lam]

I understand your point in editing the Manifest. However, my code will not even compile unless I extract everything inside swt.jar.

To better illustrate the problem:

Directory: C:\Test
Files inside Directory:

SWTHelloWorld.java

swt.jar

The compiler will not compile because it can't find the directory org/eclipse/swt/*, etc, even though they are inside swt.jar. Is there a way to compile SWTHelloWorld without extracting swt.jar?

Thank you.

[Ulf Dittmer]

Are you using the -classpath switch? It should work with something like

javac -classpath swt.jar SWTHelloWorld.java

[ManChun Lam]

Thanks, that solves the compiling problem but when running it

java SWTHelloWorld

I get this error,

Exception in thread "main" java.lang.NoClassDefFoundError: org/eclipse/swt/widgets/Composite
Caused by: java.lang.ClassNotFoundException: org.eclipse.swt.widgets.Composite
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClassInternal(Unknown Source)

If I compile and run it with swt.jar extracted, everything is fine.

Am I missing something?

Thank you for your help.

[Ulf Dittmer]

You need to specify the classpath for compilation and at runtime:

java -classpath .;swt.jar SWTHelloWorld

Note that the dot is important, otherwise the SWTHelloWorld class won't get found. (This assumes that you're using Windows; if you're on Unix, use a colon instead of a semicolon.)

[ManChun Lam]

That solves my problem. Thank you very much for your help.

ManChun Lam