exception in ClassLoader executing jar outside of build environment

Question

A simple Cassandra client app using netflix astyanax driver is built in Eclipse. Here is the pom.xml file:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>CCL1</groupId>
  <artifactId>CCL10</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <name>CassandraCL1</name>
  <description>Cassandra Client 1</description>

    <dependencies>
        <dependency>
            <groupId>com.netflix.astyanax</groupId>
            <artifactId>astyanax</artifactId>
            <version>1.56.44</version>
        </dependency>
     </dependencies>      

</project>

The app works fine when started from Eclipse. But when the jar file is copied to an external machine it fails to start with the following exception:

ubuntu@ip-172-31-31-41:~/tmp$ java -cp ./CCL10-0.0.1-SNAPSHOT.jar AppCCL1
Exception in thread "main" java.lang.NoClassDefFoundError: com/netflix/astyanax/connectionpool/exceptions/ConnectionException
        at java.lang.Class.getDeclaredMethods0(Native Method)
        at java.lang.Class.privateGetDeclaredMethods(Unknown Source)
        at java.lang.Class.getMethod0(Unknown Source)
        at java.lang.Class.getMethod(Unknown Source)
        at sun.launcher.LauncherHelper.getMainMethod(Unknown Source)
        at sun.launcher.LauncherHelper.checkAndLoadMain(Unknown Source)
Caused by: java.lang.ClassNotFoundException: com.netflix.astyanax.connectionpool.exceptions.ConnectionException
        at java.net.URLClassLoader$1.run(Unknown Source)
        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)
        ... 6 more

The external machine is Amazon t1.micro Ubuntu-12 instance. The only software installed there is Oracle’s Java Runtime Environment 1.7. It looks like some dependency is missing, but I cannot even see the name of the missing class.

Why did Maven fail to insert some dependency in jar? How do I troubleshoot and resolve such a problem?

score 0 · Accepted Answer · edited May 23 '17 at 11:57

It turns out Maven does not include all the dependencies in jar. (I assumed Maven does this automatically). Including all dependencies in jar is explained here:

How can I create an executable JAR with dependencies using Maven?

So I solved the problem by adding the following fragment in my xml file:

<build>
  <plugins>
<plugin>
  <artifactId>maven-assembly-plugin</artifactId>
  <configuration>
    <archive>
      <manifest>
        <mainClass>AppCCL1</mainClass>
      </manifest>
    </archive>
    <descriptorRefs>
      <descriptorRef>jar-with-dependencies</descriptorRef>
    </descriptorRefs>
  </configuration>
  <executions>
    <execution>
      <id>make-assembly</id> <!-- this is used for inheritance merges -->
      <phase>package</phase> <!-- bind to the packaging phase -->
      <goals>
        <goal>single</goal>
      </goals>
    </execution>
  </executions>
    </plugin>
  </plugins>
</build>

exception in ClassLoader executing jar outside of build environment

1 Answers1