Symptoms

Both Application server and Confluence can run, but accessing Confluence will result in 'Unsupported major.minor version 49.0'. The following appears in the atlassian-confluence.log:

javax.servlet.ServletException: org/apache/jsp/default_jsp (Unsupported major.minor version 49.0)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:273)
caused by: java.lang.UnsupportedClassVersionError: org/apache/jsp/default_jsp (Unsupported major.minor version 49.0)
at java.lang.ClassLoader.defineClass0(Native Method)

Cause

This is due to an incompatible JVM version. '49' is a specific JVM error, it means that the Java files in <confluencestd-install>\work were compiled with a different version of Java (for example Java 5). Hence, using an earlier version of JVM (for example JVM 1.4) would be incompatible as the binaries (*.class) will not be recognized.

Resolution

There are three ways to solve this:

1. If you really need to use the earlier version Java you would need to force Confluence to rebuild and recompile using that Java version. This is achievable via deleting the <confluence-std-install>\ work\standalone folder and run tomcat again as it will recompile on the run.
2. Revert to the original Java you were using
3. Use a later version of Java