启动Cassandra 2.0.6时出现UnsupportedClassVersionError

Question

I'm fully aware that this question has already been asked in a way in this thread:

Cassandra:UnsupportedClassVersionError

However, the answer/s given there, which I accept, don't solve my problem as I do have a current version of Java as detailed below:

 D:\\Development\\Cassandra\\apache-cassandra-2.0.6>java -version 

java version "1.7.0_45" Java(TM) SE Runtime Environment (build 1.7.0_45-b18) Java HotSpot(TM) Client VM (build 24.45-b08, mixed mode, sharing)

Knowing this, I still receive the error when starting Cassandra:

D:\\Development\\Cassandra\\apache-cassandra-2.0.6>bin\\cassandra -f Starting Cassandra Server Exception in thread "main" java.lang.UnsupportedClassVersionError: org/apache/cassandra/service/CassandraDaemon : 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 ma in class: org.apache.cassandra.service.CassandraDaemon. Program will exit.

I'm running on a Windows XP machine using the command prompt (not Cygwin) to start Cassandra and I'm able to start older versions of Cassandra without any issue (apache-cassandra-1.1.4). Am I doing something incorrect with the later version of Cassandra or have I missed something somewhere in my configuration that is blindingly obvious?

Answer 1

The only plausible explanation for that exception is that a Java 6 (or earlier) JVM is being use to run code that was compiled for the Java 7 target platform.

This contradicts what you believe to be happening. Nevertheless, it is the only plausible explanation.

I suggest that you make a copy of the cassandra wrapper script (in the same directory), and hack it to:

1. add set -x at the start to see what commands are actually being run by the script.

2. add echo $PATH , echo $JAVA_HOME and so on to see what the key environment variables are in the script's environment.

3. add a line to run java -version using the exact same command path that is being use to run the JVM for real.

This should reveal which of your beliefs / assumptions about what is happening are incorrect.

Answer 2

我确实尝试了卸载Java 1.7并安装了最新的Java 8，从而解决了我的问题。