The dreaded java.lang.NoClassDefFoundError

Question

I've looked through many of the existing threads about this error, but still no luck. I'm not even trying to package a jar or use any third-party packaging tools. I'm simply running from within Eclipse (works great) and then trying to run the exact same app from the command line, in the same location it's built to (getting this error). My goal is to be able to zip up the bin folder and send it off to be run by someone else via a command line script. Some details:

• It's a command-line app and I'm using the commons-lang-2.4.jar for string utilities. That is the file that cannot be located (specificaly "java.lang.NoClassDefFoundError: org/apache/commons/lang/StringEscapeUtils")
• I have that jar in my lib folder and have added it to my build path in Eclipse via right-click "Build Path -> Add to Build Path"
• The .classpath file looks correct and contains the reference to the jar, but I assume that file is only used by Eclipse (contains this line: <classpathentry kind="lib" path="lib/commons-lang-2.4.jar"/>)
• Could this be related to the Eclipse working directory setting? I have some internal template files that I created that are under src/templates, and the only way I can seem to get those to be seen is by setting the project working directory to AppName/src. Maybe I should be putting those somewhere else?

Let me know if any additional info would help. Surely this is something simple, but I've wasted too much time on it at this point. This is reminding me why I originally left Java back in '05 or so...

Answer 1

Eclipse doesn't build executable java classes by default. Don't ask me why, but it probably has something to do with using their own tools.jar (somewhere in plugins/org.eclipse.core ?) so that Eclipse can run without a JDK.

You can usually go to your project bin directory and do:

java -cp . MyClass

But if you have external jars, Eclipse handles those internally in another weird way, so you'll need to add those too.

Answer 2

Eclipse does not move any of the jars in your classpath into the bin folder of your project. You need to copy the util jar into the bin folder. If you move it to the root of the bin folder, you might be able to get away without any classpath entries but it's not the recommended solution. See @BalusC's answer for good coverage of that.

Answer 3

Are you specifying the classpath to java on the command line?

$ java -cp lib/commons-lang-2.4.jar your.main.Class

Answer 4

The classpath setting you are setting in Eclispe are only for the IDE and do not affect how you application is run outside the IDE. Even if you use the Eclipse Functionality to export your application as an executable jar file there is no out of the box way to package all the jars your application depends on.

If you have packaged you application into a jar file called myapp.jar then running a command like below will run the application with the jar you depend on, if you have more than one just add them separted by ; on Windows or : on Unix:

java -jar myapp.jar -cp .;c:/pathtolibs/commons-lang-2.4.jar

If you are just running the classes directly then either run the folder containing your .class files will also need to be on the path (though I assume it already is since you are able to run the program and get errors).

Answer 5

make sure your jar commons-lang-2.4.jar in classpath and not redudance.

I ever add jar file to my classpath, and have 2 file jar in my classpath. After I delete it, work smooth

Answer 6

Consider File -> Export -> Runnable jar to create a jar file which can be invoked directly with

java -jar yourProgram.jar

There are several variants depending on your needs.