I have a maven project which I have downloaded from this link. When I make a couple changes to it, it runs perfectly from the command line when I type:
mvn clean install tomcat7:run-war -Dmaven.test.skip=true
in the directory to which the zip was extracted. (The only 2 changes required to make it work on the command line are to 1.) add a plugin tag for tomcat 7 in pom.xml and 2.) create a context.xml file in the webapp/META-INF folder. Everything else in the app remains the same as the github verion, and the app runs fine from the command line using the command given above and then typing the url in the browser.)
However, when I import the project into eclipse as an existing maven project, and then try to run the app, the app starts throwing errors related to not finding a couple of jars which are clearly in the repository. The app no longer compiles from the command line, or from eclipse. I even tried to run the app as a maven build from eclipse and even changed the maven instance eclipse uses to the freestanding maven that works from the command line instead of the embedded maven in eclipse, but the app still threw the same errors when I tried to run it.
But then, when I repeated the steps with a fresh copy of the app, the fresh copy runs fine from the command line, while the copy that eclipse touched does not compile by any method.
It seems that eclipse has made some changes to the app in the process of importing it as an existing maven project into eclipse. How can I locate the specific changes that eclipse has made to the app? I would like to be able to use eclipse as my IDE, but I cannot do so unless it can compile the code.
This answer was originally posted as a comment it turns out that resolved the OP's problem, and as He asked I'm turning into an answer.
First set your eclipse to use the JDK instead of the JRE. Just as a reference this configuration on Eclipse is Normally on Window->Preferences...->Java->Installed JREs:
Second (as you already did) change eclipse maven to look at installed maven that runs on the command line again.
I've encountered some problems with maven running with the JRE instead of the JDK. Try it and let me know. I will sleep now. Tomorrow I will see what happened.
Related
The case:
I have created a complex java project (spring boot) with maven build in IntelliJ and I was able to run it, everything was working fine. Now, as IntelliJ hasn't a community edition with spring boot, I had to move to vs code. I didn't change anything in my project, I just opened the folder (which contains the pom.xml and the src folder) in vs code and let vs code load the java project (earlier I installed all the extensions like spring boot, java, etc. for vs code).
After vs code opened the project successfully, I wanted to run it in the main method by clicking the run text (I inserted the image, that you can see the folder structure):
But as stated above, I get the famous error. I reloaded the window, I cleared the workspace, I set the JAVA_HOME and CLASSPATH variables in the env variables and tried, tried, tried it again, but no success. What the hell can I do on top of that? It worked in IntelliJ, it should work in vs code too. I use java se17. Note, that if I start a new simple project, the program get's compiled and executed without any error.
Another curiosity is, if I try to load the maven dependencies, vs code says, that it can't create the dependency tree, but if I run the mvn dependency:tree command, I get all the dependencies and it says, that the build was successful.
What is going on here?
EDIT: my antivirus program blocked maven, so, the problem with the dependency tree is now gone, but the error with the classpath remains.
I use IntelliJ IDEA CE in two environments (CentOS and Ubuntu).
The two share a project via GitHub.
In CentOS, the project is regarded as Java project? with a file build.gradle.
In the other, the project is fully managed as Gradle-Java project.
When I run a main method in CentOS, IDE just runs Java (after some compiles if are required)
On the other hand, when I run the same main method in Ubuntu, IDE activates Gradle and run that.
I think this difference happens from the module structures.. which I have not tried though....
(Am I wrong?)
One question I really want to know here is,
in CentOS, when I run a code, it shows how IDE ran the code in the Run window, like...
java [too many options] foo.target.Hoge
If I copy and paste this line, I can activate foo.target.Hoge anywhere, even where I do not set CLASSPATH because [too many options] contain that.
I always do it (I am afraid if I should not though)
However, in Ubuntu (Gradle-based environment)
the windows show only
time PM: Executing task 'Hoge.main()'...
I can not copy, paste and run it...
I want to know where I can found the actual command activated.
or.... using Gradle.. are there any simpler ways?? like
gradle run Java Hoge ...
When I run a main method in CentOS, IDE just runs Java (after some compiles if are required) On the other hand, when I run the same main method in Ubuntu, IDE activates Gradle and run that.
For Gradle-based projects this behaviour is controlled in Settings (Preferences on macOS) | Build, Execution, Deployment | Build Tools | Gradle | Build and run using option. When Gradle is set IDE uses Gradle to run and build the project. When IntelliJ is set IDE uses it's own builder and Run/Debug Configurations to run.
I'm building a simple calculator app from a tutorial/class on Pluralsight (Java Fundamentals class), which starts with a Main.java file, and adds a class file later, MathEquation.java.
I created a Git repo to track my progress, and uploaded to Github: JavaFundamentalsClass. I used GitIgnore.IO to find a Java IntelliJ .gitignore file, and everything seemed to be working fine on the original PC I was using.
However, after switching over to a different PC, with a fresh install of IDEA, I cloned down the repo from Github, and found that the project would not build and/or run. I get this error:
"C:\Program Files\RedHat\java-1.8.0-openjdk-1.8.0.191-1\bin\java.exe" -Dfile.encoding=windows-1252 -jar ""
Error: Unable to access jarfile
Process finished with exit code 1
I suspect that there is something in the .gitigore file that is keeping some of the project, dependency, or build information from being saved in the repo that keeps IDEA from having all the info it needs to build and run the Main.java correctly.
Can anyone help? You should be able to download the project from the repo linked above in it's currently broken state, including the .gitignore file.
Additional Info
I wiped my repo clean and recloned and I forgot, originally it doesn't even give me the run button (it is grayed out). I had to do a procedure with "Add Configuration" from a search I did for that to show up to get the error above.
Also, I did install java from the OpenJDK, rather than oracle. I figured with Oracle cutting off commercial development maybe start the switch now as I'm learning, but maybe that's the issue (normal Java on my other PC).
It's working, but...
First thing - Intellij needs to know where Java is. It appears that if the SDK/JDK is not installed prior to Intellij, you will need to tell it where Java is after installing. Or if you use OpenJDK instead of Oracle Java SDK. You can do that at View/Open Library Settings, under Platform Settings / SDKs (select the JDK home path).
Then, after setting up Java, I am able to get everything working in Intellij IDEA if I find the Main.java file, right-click, and choose "Run main.main()". This runs the program okay, and also creates a Main configuration in the Run/Debug configuration area, and finally the "Run" button becomes available.
So I can get it working, but if I wipe all the files and clone it fresh from the remote repo, I have to go through running the Main.java file directly again to recreate the configuration.
So, this still doesn't answer my original question. Why doesn't this configuration get saved in the repo? What file is this information saved in? Is there something in the .gitignore file that is keeping this information from being saved to the repo?
Look like you have a different java version on your second machine.
First of all, check your java version
Update the configuration of your project, right now it pointing to java 1.8
https://github.com/LightCC/JavaFundamentalsClass/blob/master/.idea/misc.xml
I think it might be because of java not installed on the other PC you were trying. If it is installed just check whether the path mentioned has java executable file.
The first part is ensuring Java is setup, and that Intellij IDEA knows where Java is, per the other answers, comments, and addendums to the question.
The second part is setting up the run/debug configuration, per the "It's working but.." section of the question. This can be created automatically by right-clicking the file that has the main class to be run (usually Main()...), and selecting the "Run Main.main()" option (replacing Main and main() with the file and function which needs to be run)
The final piece is that to get the run/debug configurations to save to the repo, you either need to:
Share the workspace.xml file (i.e. make sure this is not in the .gitignore file). However, there is a lot of user-specific stuff in that file, so it should normally be excluded from the repo.
Or, edit the configuration and checkmark the "Share" box in the upper right-hand corner (just right of the "Name" field). This will put the configuration into a separate folder inside the .idea folder, which should not be excluded from the repo by .gitignore.
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 need the Playn libraries for an important project and I can't make them work on Linux. All the first part run smooth, I've installed git, and launched the clone command from terminal, I've installed maven and the mvn test went fine, then I've installed the maven add-on for Eclipse an rebooted. Then I've created a blank project in the workspace folder with the following command
mvn archetype:generate -DarchetypeGroupId=com.googlecode.playn -DarchetypeArtifactId=playn-archetype -DarchetypeVersion=1.7
Now I only have to import it and this is where the problem start, every time I tried I get the same errors.
Now I think that I can resolve all but the last two by adding some plug-in and packages, but how can I fix the last two? This has been haunting me for days and I've even found out that is a common problem but I don't understand a word about its solution. There must be a package or something that fix that, if not I need a step by step guide on how to fix it cause I've only used Eclipse for debugging, and I've never ever messed with Playn before.
I'm running on Ubuntu 32 bit, it's the last release.