Java: Unresolved compilation problem


What are the possible causes of a "java.lang.Error: Unresolved compilation problem"?

Additional information:

I have seen this after copying a set of updated JAR files from a build on top of the existing JARs and restarting the application. The JARs are built using a Maven build process.

I would expect to see LinkageErrors or ClassNotFound errors if interfaces changed. The above error hints at some lower level problem.

A clean rebuild and redeployment fixed the problem. Could this error indicate a corrupted JAR?

Best Solution

(rewritten 2015-07-28)

The default behavior of Eclipse when compiling code with errors in it, is to generate byte code throwing the exception you see, allowing the program to be run. This is possible as Eclipse uses its own built-in compiler, instead of javac from the JDK which Apache Maven uses, and which fails the compilation completely for errors. If you use Eclipse on a Maven project which you are also working with using the command line mvn command, this may happen.

The cure is to fix the errors and recompile, before running again.

The setting is marked with a red box in this screendump:

Eclipse Preferences under OS X