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?
(rewritten 2015-07-28)
Summary: Eclipse had compiled some or all of the classes, and its compiler is more tolerant of errors.
Long explanation:
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:
try to clean the eclipse project
you just try to clean maven by command
mvn clean
and after that following command
mvn eclipse:clean eclipse:eclipse
and rebuild your project....
Your compiled classes may need to be recompiled from the source with the new jars.
Try running "mvn clean" and then rebuild
The major part is correctly answered by Thorbjørn Ravn Andersen.
This answer tries to shed light on the remaining question: how could the class file with errors end up in the jar?
Each build (Maven & javac or Eclipse) signals in its specific way when it hits a compile error, and will refuse to create a Jar file from it (or at least prominently alert you). The most likely cause for silently getting class files with errors into a jar is by concurrent operation of Maven and Eclipse.
If you have Eclipse open while running a mvn build, you should disable Project > Build Automatically until mvn completes.
EDIT:
Let's try to split the riddle into three parts:
(1) What is the meaning of "java.lang.Error: Unresolved compilation
problem"
This has been explained by Thorbjørn Ravn Andersen. There is no doubt that Eclipse found an error at compile time.
(2) How can an eclipse-compiled class file end up in jar file created
by maven (assuming maven is not configured to used ecj for
compilation)?
This could happen either by invoking Maven with no or incomplete cleaning. Or, an automatic Eclipse build could react to changes in the filesystem (done by Maven) and re-compile a class, before Maven proceeds to collect class files into the jar (this is what I meant by "concurrent operation" in my original answer).
(3) How come there is a compile error, but mvn clean succeeds?
Again several possibilities: (a) compilers don't agree whether or not the source code is legal, or (b) Eclipse compiles with broken settings like incomplete classpath, wrong Java compliance etc. Either way a sequence of refresh and clean build in Eclipse should surface the problem.
I had this error when I used a launch configuration that had an invalid classpath. In my case, I had a project that initially used Maven and thus a launch configuration had a Maven classpath element in it. I had later changed the project to use Gradle and removed the Maven classpath from the project's classpath, but the launch configuration still used it. I got this error trying to run it. Cleaning and rebuilding the project did not resolve this error. Instead, edit the launch configuration, remove the project classpath element, then add the project back to the User Entries in the classpath.
I got this error multiple times and struggled to work out. Finally, I removed the run configuration and re-added the default entries. It worked beautifully.
Just try to include package name in eclipse in case if you forgot it
Import all packages before using it, EX: import java.util.Scanner before using Scanner class.
These improvements might work and it will not give Java: Unresolved compilation problem anymore.
Also make sure to check compiler compliance level and selected jdk version is same
As a weird case, I encountered such an exception where the exception message (unresolved compilation bla bla) was hardcoded inside of generated class' itself. Decompiling the class revealed this.
I had the same issue using the visual studio Code. The root cause was backup java file was left in the same directory.
Removed the backup java file
When the build failed, selected the Fix it, it cleaned up the cache and restarted the workSpace.
When I try to import project from github to Intellij Idea, it succesfully getting.
I want to run it and see the output. But when I compile it, I get the error cannot start compilation.
Here is the picture of my error.
As I understand from the error, the output directory is not exist.
I use Project Structure --> Project compiler output to initialize it.
I described it as projectname\out. Also my compiler output is set to Inherit project compile output path.
Then I rebuild my project but it doesn't success.
I just want to run github project in Intellij Idea.
I suddenly encountered the following problem: it does not recognise certain class files from the dependencies.
Screenshot
Thinking it was because of my installation, I re-installed everything from Java to the Maven Plugin and tried to compile and run the SimpleExample from a clean project. Which gives the following result: Screenshot and the following exception: Screenshot
Your project is missing the dependency rinsim-core with groupId com.github.rinde.
Check with dependency:list if it is present. If not, add it.
If it is already there, try to compile the project outside eclipse. Install a command line maven, navigate to the directory, do mvn clean package and report any error you get as a comment under this answer.
I'am trying to import a class but the Eclipse doesn't recognize the downloaded libraries. I have tried to Update my Maven's project via Maven-> Update Project it did not help. I tried to remove all dependencies except selenium-java and it did not help as well as redownloading the project from repository after a maven project update. Please need a hand, have no ideas what else should i do?
P.S. I tried to download the project on another machine and for first it didn't work but after a second attempt it went well and compiled.
Screenshot of the error:
Try inspecting /org/seleniumhq/selenium/selenium-firefox-driver/3.8.1/selenium-firefox-driver-3.8.1.jar in your local Maven repository. Perhaps it's corrupted.
You can also try building the project from command line. Simple mvn clean install in command line should print the same error as you get in Eclipse. This will confirm that you don't have problems with your Eclipse setup.
1 . Check the Build path if it looks like image
Or 2. if you can not see the highlighted class as
In this case re download the selenium jar or download another build
Ok, first up I am almost completely unfamiliar with Java and Java tooling.
I am attempting to contribute a bugfix to a Jenkins plugin. Code-wise the fix is simple, my problem is in trying to compile the project and run the tests locally.
I have installed IntelliJ IDEA 15CE and started a new project, pointing it to my local clone of the plugin repo.
It has gone away and 'downloaded the internet' in terms of Maven dependencies. Mostly everything looks ok. What I want to do is to run the tests...
If I right-click at the root of the project and select 'Run All Tests' I get the error:
Error:(115, 29) java: cannot find symbol
symbol: variable Messages
location: class hudson.plugins.copyartifact.BuildSelector
The source of this error is a line:
console.println(Messages.CopyArtifact_MissingSrcArtifacts(srcDir));
https://github.com/jenkinsci/copyartifact-plugin/blob/master/src/main/java/hudson/plugins/copyartifact/BuildSelector.java#L115
As far as I can tell the Messages symbol should resolve to this properties file:
https://github.com/jenkinsci/copyartifact-plugin/blob/master/src/main/resources/hudson/plugins/copyartifact/Messages.properties
...which IDEA recognises as a 'Resource Bundle' in the project tree view.
But it doesn't seem to recognise it when compiling the project.
I have no idea where to start fixing this. The tests run fine if I push a commit to a pull request on GitHub and let the cloudbees.com Jenkins server run them, but I'd like to be able to test stuff locally first.
Run the maven compile command from Intelli-J Maven tool. After compiling error will vanish.
When you compile it will generate a Messages.java file in generated sources automatically.