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.
I was writing a simple class HelloPrinter3.java. It's in directory src/two. Now IntelliJ is giving me an error, saying Package name 'three' does not correspond to the file path 'two'. But it also compiles and runs fine.
I already know that a package name should not necessarily be the folder name. But what I am confused is the error. It cannot be the java error as the file would not have run. But then is it IntelliJ error? How can I differentiate between these two errors while writing code? Thanks in advance.
This IDE inspection detects package statements that do not correspond to the project directory structure. Also, reports classes without package statements if the class is not located directly in source root directory.
While it's not strictly mandated by Java language, it's good to keep classes from package com.example.myapp inside the com/example/myapp directory under the source root. Failure to do this may confuse code readers and make some tools working incorrectly.
You can point the cursor at package three and press Alt + Enter to see which fixes the IDE suggest:
Also, you can disable this inspection in the IDE settings if needed:
I try to import module from existing sources, but got "The project is already registered" error message. I have another 2 sources what I could import in the same way. Only that one causes this problem. Technically there are no differences among these 3 modules.
The main problem could be that once I imported this source as a project instead of module. I suppose that the issue is relating to this failure.
I can't force Idea to forget this cached setting. Following some tip found on internet I tried a lot of things to do so...
From Idea side:
Closed the project
Clear recent projects
Gradle refresh / clean etc.
From file system side:
I removed .idea folder from the folder of that source
I cleaned up the wrong project name from every human readable file in .IdeaIC2017.1 folder
Uninstall Idea with cache cleanup, then download/install the recent version 2017.2. Even after this step the problem remained!!!!
I don't have so much experience with Idea, but this doesn't help getting love it...
I stucked. Please help!
We are using Code Analysis on our projects. As part of this we have Code Analysis enabled on the build server allowing for continious checks.
Now we are receiving this error:
CA0063 : * Failed to load rule set file '[name].ruleset' or one of its
dependent rule set files.
[name] being a ruleset on our internal network, available for everyone.
Code Analysis runs perfectly fine on each local machine, but not on the build server. How can we fix this issue?
Notes:
We use a custom made ruleset
We are not using any custom rules (yet)
I was having this issue as well. How I solved it was to add my custom ruleset into version control (Git) as a new directory within my project files. We are using Jenkins for our CI, so in my Jenkins.build I then made sure to specify the absolute file path to my ruleset on the Jenkins server, which you can get by looking at your Workspace on Jenkins. For example the path may look like :
e:\Jenkins\workspace\SampleProj-Dev\Rulesets\CustomRules.ruleset
In Jenkins.build file, I added an argument to the msbuild.exe program execution with:
<arg line="/p:RunCodeAnalysis=true;CodeAnalysisRuleSet=e:\Jenkins\workspace\SampleProject-Dev\Rulesets\CustomRules.ruleset"/>
Before I had tried using a relative path but with a build containing many sub-projects, Jenkins tried to append the path onto a changing path. This path was based on the currently building sub-project, resulting in the same error you received.
I stumbled onto a fix for this tonight for a project that has been suffering from it for ages. I created a new configuration CHECKED and the problem disappeared. Then by:
Deleting the existing configurations from Configuration Manger;
Exiting and saving (this step might not be necessary); and finally
Recreating the dropped configurations from the newly created one, CHECKED
the problem has now disappeared completely in all configurations.
This was all in Visual Studio 2013.
my issue is very similar to:
http://www.dotnetmonster.com/Uwe/Forum.aspx/dotnet-vb/54944/VB-Net-project-throwing-errors-when-executing-Clean-Solution
Typical errors: Unable to load referenced library X
Type IWshRuntimeLibrary.WshShell is not defined.
Interface System.IDisposable is not implemented by this class.
Namespace of type specified in the Imports Z does not contain any public members or cannot be found. Make sure the imported element name does not use any aliases.
This must have to do with a VB.net project configuration. Currently there is a setting "Treat all warnings as errors". I would like to keep that setting, but also resolve these annoying "errors".
I've experienced a similar problem and fixed it by running the following command in the VS command line tool
devenv /resetskippkgs
I'ev had problems executing Clean's via MSBuild in VS2008 when projects were registered for COM interop.
The problem is that the "Clean" target auto-generated for a solution cleans projects in the same order in which they were built.
This causes problems for projects registered for COM when MSBuild attempts to load and then unregister the assembly from COM during a "Clean".The issue occurs if the assembly has a dependency on another project because the dependency will be deleted first and therefore loading the assembly will fail and MSBuild will be unable to unregister it.
A workaround is to change the solution .cache file (which contains the targets auto-generated by MSBuild during "Build") and reverse the order of the "Clean" target. I hacked-together a quick-fix custom build task to do this as a post-build step.
No idea if this was fixed in VS2010 or indeed if this matches your problem since you don't give many specifics in your question ;)