I am trying to package a simple maven java project (uses javax.persistence api) into a single jar using the onejar-maven-plugin. I can run the program fine in eclipse; however when execute the onejar I get the exception below. If someone could provide some insight, that would be appreciated. Thanks, RG Exception in thread "main" java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at com.simontuffs.onejar.Boot.run(Boot.java:306) at com.simontuffs.onejar.Boot.main(Boot.java:159) Caused by: Exception [EclipseLink-30005] (Eclipse Persistence Services - 2.0.0.v20091127-r5931): org.eclipse.persistence.exceptions.PersistenceUnitLoadingExcept Exception Description: An exception was thrown while searching for persistence archives with ClassLoader: com.simontuffs.onejar.JarClassLoader@190d11 Internal Exception: java.lang.ClassCastException: sun.misc.Launcher$AppClassLoader cannot be cast to com.simontuffs.onejar.JarClassLoader at org.eclipse.persistence.exceptions.PersistenceUnitLoadingException.exceptionSearchingForPersistenceResources(PersistenceUnitLoadingException.java:126 at org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactory(PersistenceProvider.java:133) at org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactory(PersistenceProvider.java:65) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:78) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:54) at com.test.onejartest.App.main(App.java:19) ... 6 more Caused by: java.lang.ClassCastException: sun.misc.Launcher$AppClassLoader cannot be cast to com.simontuffs.onejar.JarClassLoader at com.simontuffs.onejar.JarClassLoader.getByteStream(JarClassLoader.java:753) at com.simontuffs.onejar.Handler$1.getInputStream(Handler.java:50) at java.net.URL.openStream(Unknown Source) at org.eclipse.persistence.internal.jpa.deployment.ArchiveFactoryImpl.isJarInputStream(ArchiveFactoryImpl.java:124) at org.eclipse.persistence.internal.jpa.deployment.ArchiveFactoryImpl.createArchive(ArchiveFactoryImpl.java:106) at org.eclipse.persistence.internal.jpa.deployment.PersistenceUnitProcessor.findPersistenceArchives(PersistenceUnitProcessor.java:213) at org.eclipse.persistence.internal.jpa.deployment.JPAInitializer.findPersistenceUnitInfoInArchives(JPAInitializer.java:134) at org.eclipse.persistence.internal.jpa.deployment.JPAInitializer.findPersistenceUnitInfo(JPAInitializer.java:125) at org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactory(PersistenceProvider.java:98) ... 10 more pom.xml: ... <pluginRepositories> <pluginRepository> <id>onejar-maven-plugin.googlecode.com</id> <url>http://onejar-maven-plugin.googlecode.com/svn/mavenrepo</url> </pluginRepository> </pluginRepositories> ... <build> <plugins> <plugin> <groupId>org.dstovall</groupId> <artifactId>onejar-maven-plugin</artifactId> <version>1.3.0</version> <executions> <execution> <configuration> <mainClass>com.test.onejartest.App</mainClass> </configuration> <goals> <goal>one-jar</goal> </goals> </execution> </executions> </plugin> <plugin> <artifactId>maven-compiler-plugin</artifactId> <version>2.3.1</version> <configuration> <target>1.6</target> <source>1.6</source> </configuration> </plugin> </plugins> </build> ... <dependencies> <dependency> <groupId>javax.persistence</groupId> <artifactId>persistence-api</artifactId> <version>2.0.0</version> </dependency> <dependency> <groupId>org.eclipse.persistence</groupId> <artifactId>eclipselink</artifactId> <version>2.0.0</version> </dependency> <dependency> <groupId>com.microsoft.sqlserver.jdbc</groupId> <artifactId>sqljdbc</artifactId> <version>4.0.0</version> </dependency> </dependencies>