jython @2.7.0: Unsupported major.minor version 51.0

[mfacorcoran]

I tried to install jython but the install failed:

% sudo port install jython
Warning: xcodebuild exists but failed to execute
Warning: Xcode does not appear to be installed; most ports will likely fail to build.
--->  Computing dependencies for jython
--->  Building jython
Error: Failed to build jython: command execution failed
Error: See /opt/local/var/macports/logs/_opt_local_var_macports_sources_github.com_macports_macports-ports_lang_jython/jython/main.log for details.
Error: Follow https://guide.macports.org/#project.tickets to report a bug.
Error: Processing of port jython failed

[mf2k (Frank Schima)]

In the future, please fill in the Port field.

[ryandesign (Ryan Carsten Schmidt)]

The log says:

Exception in thread "main" java.lang.UnsupportedClassVersionError: org/python/util/install/Installation : Unsupported major.minor version 51.0

That's not very clear to me (it doesn't say what thing "51.0" is the version of, or what versions of that thing are supported), but according to ​this page I think it means you have the wrong version of the JDK installed. What version do you have installed? Can you try a newer or older version?

[chrstphrchvz (Christopher Chavez)]

I agree that the cause of this is that Java 6 or older is being used, whereas Java 7 is required by the current Jython. I have opened a pull request that forces Java 8 to be used (since it is currently only possible to specify a single version rather than a maximum version using the Java portgroup): ​https://github.com/macports/macports-ports/pull/5130

[chrstphrchvz (Christopher Chavez)]

In ec6a567b2687f85318fef9ac1939079579968866/macports-ports (master):

jython: always use Java portgroup

…even for the -installer variant to eliminate fallback dependency
on jikes; use openjdk8 as fallback.
Add note explaining current/future Java version compatibility.

Closes: #53963