ClassNotFoundException problems with manifest in created JAR

Question

I'm trying to create a JAR file from my sources, but when I run it I get class not found exception - it can't find the main class, even though I defined it in the MANIFEST.MF file. Can you spot any errors please?

My JAR structure:

META-INF/
META-INF/MANIFEST.MF
main/
main/java/
main/java/ThreadWatcher.java
main/java/WatcherObject.java
main/resources/
main/resources/WatcherObjectType.java
main/resources/TLogger.java
main/resources/DataProvider.java
main/resources/WatcherObjectStatus.java
main/resources/SettingsProvider.java

main/java/WatcherObject.java contains the main method.

My MANIFEST.MF:

Manifest-Version: 1.0
Created-By: 1.6.0_27 (Sun Microsystems Inc.)
Main-Class: main.java.ThreadWatcher

When I run it I get:

Exception in thread "main" java.lang.NoClassDefFoundError: main/java/ThreadWatcher
Caused by: java.lang.ClassNotFoundException: main.java.ThreadWatcher
    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)
Could not find the main class: main.java.ThreadWatcher. Program will exit.

Thanks for help!

Answer 1

The problem is most likely that you're including java source files, rather than the compiled classfiles. When you load a class, the JVM by default looks for a classfile with that given name and tries to load it. Since you don't have any classfiles, it can't load the class.