尝试使用java.exe -jar运行我的jar时出现NoClassDefFoundError ...怎么了？

Question

I have an application that I'm trying to wrap into a jar for easier deployment. The application compiles and runs fine (in a Windows cmd window) when run as a set of classes reachable from the CLASSPATH. But when I jar up my classes and try to run it with java 1.6 in the same cmd window, I start getting exceptions:

C:\dev\myapp\src\common\datagen>C:/apps/jdk1.6.0_07/bin/java.exe -classpath C:\myapp\libs\commons -logging-1.1.jar -server -jar DataGen.jar
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory
    at com.example.myapp.fomc.common.datagen.DataGenerationTest.<clinit>(Unknown Source)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory
    at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:276)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
    at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
    ... 1 more

The funny thing is, the offending LogFactory seems to be in commons-logging-1.1.jar, which is in the class path specified. The jar file (yep, it's really there):

C:\dev\myapp\src\common\datagen>dir C:\myapp\libs\commons-logging-1.1.jar
 Volume in drive C is Local Disk
 Volume Serial Number is ECCD-A6A7

 Directory of C:\myapp\libs

12/11/2007  11:46 AM            52,915 commons-logging-1.1.jar
           1 File(s)         52,915 bytes
           0 Dir(s)  10,956,947,456 bytes free

The contents of the commons-logging-1.1.jar file:

C:\dev\myapp\src\common\datagen>jar -tf C:\myapp\libs\commons-logging-1.1.jar
META-INF/
META-INF/MANIFEST.MF
org/
org/apache/
org/apache/commons/
org/apache/commons/logging/
org/apache/commons/logging/impl/
META-INF/LICENSE.txt
META-INF/NOTICE.txt
org/apache/commons/logging/Log.class
org/apache/commons/logging/LogConfigurationException.class
org/apache/commons/logging/LogFactory$1.class
org/apache/commons/logging/LogFactory$2.class
org/apache/commons/logging/LogFactory$3.class
org/apache/commons/logging/LogFactory$4.class
org/apache/commons/logging/LogFactory$5.class
org/apache/commons/logging/LogFactory.class
... (more classes in commons-logging-1.1 ...)

Yep, commons-logging has the LogFactory class. And finally, the contents of my jar's manifest:

Manifest-Version: 1.0
Ant-Version: Apache Ant 1.6.5
Created-By: 10.0-b23 (Sun Microsystems Inc.)
Main-Class: com.example.myapp.fomc.common.datagen.DataGenerationTest
Class-Path: commons-logging-1.1.jar commons-lang.jar antlr.jar toplink
 .jar GroboTestingJUnit-1.2.1-core.jar junit.jar

This has stumped me, and any coworkers I've bugged for more than a day now. Just to cull the answers, for now at least, third party solutions to this are probably out due to licensing restrictions and company policies (eg: tools for creating exe's or packaging up jars). The ultimate goal is to create a jar that can be copied from my development Windows box to a Linux server (with any dependent jars) and used to populate a database (so classpaths may wind up being different between development and deployment environments). Any clues to this mystery would be greatly appreciated!

Answer 1

The -jar option is mutually exclusive of -classpath. See an old description here

-jar

Execute a program encapsulated in a JAR file. The first argument is the name of a JAR file instead of a startup class name. In order for this option to work, the manifest of the JAR file must contain a line of the form Main-Class: classname. Here, classname identifies the class having the public static void main(String[] args) method that serves as your application's starting point.

See the Jar tool reference page and the Jar trail of the Java Tutorial for information about working with Jar files and Jar-file manifests.

When you use this option, the JAR file is the source of all user classes, and other user class path settings are ignored.

A quick and dirty hack is to append your classpath to the bootstrap classpath:

-Xbootclasspath/a: path

Specify a colon-separated path of directires, JAR archives, and ZIP archives to append to the default bootstrap class path.

However, as @Dan rightly says, the correct solution is to ensure your JARs Manifest contains the classpath for all JARs it will need.

Answer 2

您可以省略-jar选项，然后像下面那样启动jar文件：

java -cp MyJar.jar;C:\\externalJars\\* mainpackage.MyMainClass

Answer 3

This is the problem that is occurring,

if the JAR file was loaded from "C:\\java\\apps\\appli.jar", and your manifest file has the Class-Path: reference "lib/other.jar", the class loader will look in "C:\\java\\apps\\lib\\" for "other.jar". It won't look at the JAR file entry "lib/other.jar".

Solution:-

1. Right click on project, Select Export.
2. Select Java Folder and in it select Runnable JAR File instead of JAR file.
3. Select the proper options and in the Library Handling section select the 3rd option ie (Copy required libraries into a sub-folder next to the generated JAR).

[ EDIT = 3rd option generates a folder in addition to the jar, 2nd option ("Package required libraries into generated JAR") can also be used as you have the jar. ]

4. Click finish and your JAR is created at the specified position along with a folder that contains the JARS mentioned in the manifest file.

5. open the terminal,give the proper path to your jar and run it using this command java -jar abc.jar

   Now what will happen is the class loader will look in the correct folder for the referenced JARS since now they are present in the same folder that contains your app JAR..There is no "java.lang.NoClassDefFoundError" exception thrown now.

This worked for me... Hope it works for you too!!!

Answer 4

if you use external libraries in your program and you try to pack all together in a jar file it's not that simple, because of classpath issues etc.

I'd prefer to use OneJar for this issue.

Answer 5

i had the same problem with my jar the solution

1. Create the MANIFEST.MF file:

Manifest-Version: 1.0

Sealed: true

Class-Path: . lib/jarX1.jar lib/jarX2.jar lib/jarX3.jar

Main-Class: com.MainClass

2. Right click on project, Select Export.

select export all outpout folders for checked project

3. select using existing manifest from workspace and select the MANIFEST.MF file

This worked for me :)

Answer 6

I have found when I am using a manifest that the listing of jars for the classpath need to have a space after the listing of each jar eg "required_lib/sun/pop3.jar required_lib/sun/smtp.jar ". Even if it is the last in the list.