Classpath is set, but still getting NoClassDefFoundError

问题

I'm trying to package a very simple app into a jar to distribute to a user. I'm using Eclipse Indigo with the m2e plugin on Mac OS X 10.6.8.

I used the Maven build: package goal to package it as a jar. If I double click on the jar to open it, the GUI opens and appears to be working, but when I click the execute button, nothing happens. (The program works fine if I do Run As... within Eclipse).

If I try to run the jar from the command line, it won't even open the GUI, I get this error:

Exception in thread "main" java.lang.NoClassDefFoundError: str-profile-comparison-0/0/1-SNAPSHOT    /jar
Caused by: java.lang.ClassNotFoundException: str-profile-comparison-0.0.1-SNAPSHOT.jar
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:248)

I extracted the manifest file from the jar, to check the classpath, and it looks like this:

Manifest-Version: 1.0
Built-By: username
Build-Jdk: 1.6.0_24
Class-Path: poi-3.7.jar poi-ooxml-3.7.jar poi-examples-3.7.jar xmlbean
s-2.3.0.jar stax-api-1.0.1.jar dom4j-1.6.1.jar xml-apis-1.0.b2.jar po
i-ooxml-schemas-3.7.jar geronimo-stax-api_1.0_spec-1.0.jar poi-scratc
hpad-3.7.jar junit-4.8.2.jar
Created-By: Apache Maven
Main-Class: com.{companyname}.strprofilecomparison.logic.StrComparatorGUI
key: value
url:
mode: development
Archiver-Version: Plexus Archiver

I have several questions about what is happening here:

Why does the GUI open when I double-click the jar file, but not when I try to run it at the command line?
I'm guessing the classpath needs to define the absolute path to the external jars I'm using, how do I set that in the POM file?

Thanks!

回答1:

That manifest says that all your dependencies are sitting in the same dir as your jar. If that's not true, no go.

Personally, I'd use the appassembler plugin to make a device that has a shell script to launch it. Or the shade plugin to make an uberjar that just incorporates them. Or learn about OSX stubs to make an OSX proper .app application.

来源：https://stackoverflow.com/questions/10808209/classpath-is-set-but-still-getting-noclassdeffounderror

标签

java

maven

jar

classpath