Why jar doesn't work with command line?

Question

I'm making a project to modify a .wav file to .flac file, I use the class http://javaflacencoder.sourceforge.net/javadoc/index.html. My project in IDE eclipse works well. But when I exported it into .jar and run it with command line on linux. There is the error:

 Exception in thread "main" java.lang.NoClassDefFoundError: javaFlacEncoder/FLAC_FileEncoder
    at speech.Speech.main(Speech.java:44)
Caused by: java.lang.ClassNotFoundException: javaFlacEncoder.FLAC_FileEncoder
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
    ... 1 more

Without idea, I can't understand why. Could anybody have the same problem? Could you show me how to resolve it? Thanks,

Whats the command you're typing on terminal? Does your project reference any external libs? Try adding -cp PATH of your libs. — AndreDuarte, Sep 12 '14 at 13:08
look at the FAQ http://stackoverflow.com/questions/34413/why-am-i-getting-a-noclassdeffounderror-in-java — Martin Frank, Sep 12 '14 at 13:10
@AndreDuarte: I use this command line: java -jar project.jar Audio.wav. When I created the project, I have added some externel libraries. Could you show more clearly how to add -cp PATH in my libs? Sorry for this basic question, I'm beginning on linux :) — VUONG Tam, Sep 12 '14 at 13:17

score 0 · Answer 1 · answered Sep 12 '14 at 13:11

Eclipse takes care of setting up the classpath for the execution of your Java program; you probably failed to replicate this on the command line. There are several options:

if starting with java <main_class_name>, then add the -cp argument listing all the dependency JARs;
if starting with java -jar <jar_name>, then make sure the JAR's manifest (MANIFEST.MF) includes the Class-Path entry, which lists the other JARs it depends on;
create an "uberjar" which contains all the necessary classes. Maven's shade plugin can do that for you.

score 0 · Accepted Answer · answered Sep 12 '14 at 13:12

You should probably add a classpath entry to let Java know of your librarie.

Typically, you must do:

# generate the classpath entry
declare classpath=$(for jar in lib/*.jar; do echo ":$jar"; done)
# remove the first character (':').
classpath="${classpath:1}"
java -cp "${classpath}" -jar yourjar.jar

Or:

# the same code that generate classpath
export CLASSPATH="${classpath}"
java -jar yourjar.jar

Also, in the manifest of the jar, you can list them the Class-Path entry.

Why jar doesn't work with command line?

2 Answers2