Jetty running on 1.6 JVM is unable to run webapp compiled on Java 1.6
java, jetty, jvm, tomcat
Solution
Jetty 9 requires to be ran with Java 7, according to this list of Jetty versions.
You can try to compile Jetty 9 yourself using Java 6, but that will most likely not work (otherwise, the Jetty devs might've done that themselves as well).
Problem
I am trying to start very simple Java webapp on Jetty (v9.0) webserver. Using maven I built and created the war and as can be see in the manifest file, I used Java 1.6u43 for compilation on OS X Contents of META-INF/MANIFEST.MF ``` Manifest-Version: 1.0 Archiver-Version: Plexus Archiver Created-By: Apache Maven Built-By: irraju Build-Jdk: 1.6.0_43 ``` I am running Jetty on Ubuntu and as can be seen, I have slightly higher version of the java 1.6.0_45. If java is backward compatible, my java application should run on jetty but it is failing with unsupported minor version ``` root# java -version java version "1.6.0_45" Java(TM) SE Runtime Environment (build 1.6.0_45-b06) Java HotSpot(TM) Client VM (build 20.45-b01, mixed mode, sharing) root# java -DDEBUG -jar start.jar Exception in thread "main" java.lang.UnsupportedClassVersionError: org/eclipse/jetty/start/Main : Unsupported major.minor version 51.0 at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631) at java.lang.ClassLoader.defineClass(ClassLoader.java:615) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141) at java.net.URLClassLoader.defineClass(URLClassLoader.java:283) at java.net.URLClassLoader.access$000(URLClassLoader.java:58) at java.net.URLClassLoader$1.run(URLClassLoader.java:197) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) Could not find the main class: org.eclipse.jetty.start.Main. Program will exit. ``` Other people on the internet are facing this issue when they are trying to run Java 1.7 compiled applications on 1.6* JVMs. I am unable to figure out why this is happening in my case where both the ENVs are 1.6* and deployment ENV has slightly higher version of JVM. If I deploy the application on Tomcat that is using java 1.6.0_45, it doesn't complain though and works fine. Am I missing something very trivial here?