Develop Reference

Any command to install all missing files for maven project in .M2 folder?

My maven project environment was set up few months back in working condition and then I deleted my m2 folder to create a different set up of environment other project. Now, I am trying to access the maven project environment but so many dependency files missing errors are thrown.
Any idea about the command which actually installs or gets the missing files from whole system ?
or any other way ?

If you deleted the maven repo, than you have to uninstall/install it back.
Or you have deleted the jars in User/m2/repository/com... than just simply build the project.

From your question, we see either
You have deleted the Maven Source Files
You have deleted the Project dependency files
In first case, delete / uninstall the Maven from your system, and install a fresh package.
In the Second case, nothing to worry, just clean install for the project. Also, you could point the local repository to
<localRepository>c:\Maven\repository</localRepository>
in your POM

Why can I not access all plugins in my target definition?

I have a problem concerning target definitions in Eclipse. I want to use plugin version 1.0.0, which is in my target platform definition, while I have the plugin project in my workspace with version 1.0.2. For all other plugins in my target definition, everything works as expected (which I see because an error gets flagged if something's missing), but this specific one, Eclipse does not make available to my projects. Only the plugin version 1.0.2 is. The plugin is not set as a singleton.
Why is this and how can I resolve this problem?
I figured out that I can access the right version when I close the project that contains the wrong one - but this is awkward, is there another way?
It seems that it's actually not an eclipse-specific problem, it fails also when building on the command line through maven/tycho. Specifically, my target platform is the Juno Release. Are there plugins that, while part of a feature, are not made available to other bundles? I know the plugin is there, but neither tycho nor Eclipse want to make it available to me.
Maybe I should also say it fails at compile time.
While, as I said, there exist workarounds for the problem, I still would like to have a "nice" solution to this problem. You can check out the project together with the target definition at https://github.com/kutschkem/Jayes
You may also need to check out and build this project first:
git clone http://git.eclipse.org/gitroot/recommenders/org.eclipse.recommenders.git
After setting the target platform, try building something with Jayes 1.0.0 (which is in the target platform) instead of Jayes 1.0.2 (which is in your workspace). You can also try to build with maven, it doesn't work as well.
Known workarounds:
Close the Jayes 1.0.2 project. Then, eclipse lets you use Jayes 1.0.0
For running an (OSGi) application, you can choose which bundles are loaded. You can choose version 1.0.0 manually there
Using a product definition, you can access the same runtime configuration as for workaround 2
If someone finds a workaround for maven, I'd be happy to know about it.

Maybe you have set your plugin to be singleton, so there will only be one instance for the bundle with a specific id.
You can change this by remove the "singleton:=true" in your MANIFEST.MF.
Bundle-SymbolicName: org.eclipse.xxx; singleton:=true
Or, you could remove the 1.0.2 version plugin from the run configuration when start running. click run --> run configuration to open the run configuration dialgo, switch to 'plugins' tab, here you can select which of these plugins you want to use .

I think you have already tried the following, but a reload of the target platform might help.
Also, what does your feature.xml file specify for version of that plugin?

Using maven-release-plugin in Eclipse

I recently tried to use maven-release-plugin since it is apparently the recommended way of building and packages releases in the Maven universe.
However I wanted to use this within Eclipse, as the rest of my development workflow is Eclipse based. I normally run Maven commands via the m2eclipse plugin provided as part of Eclipse Juno (4.2)
I noticed a few oddities when I tried to run "release:prepare" within Eclipse:
Some extra files were created in the root project directory - "pom.xml.releaseBackup" and "release.properties". Do they really belong there? Have I got the release directories set up correctly? I wouldn't really consider these temporary artifacts as part of my source code tree......
The pom.xml gets manually overwritten with the updated release number. Eclipse warns you and is happy to reload the updated version - but is this generally safe?
The prepare ultimately fails giving the error [ERROR] Failed to execute goal org.apache.maven.plugins:maven-release-plugin:2.0:prepare (default-cli) on project clisk: Failed to invoke Maven build. Error configuring command-line. Reason: Maven executable not found at: C:\Users\Mike\git\clisk\EMBEDDED\bin\mvn.bat -> [Help 1] - presumably because I am using the built-in Maven excetable provided by m2eclipse rather than the command line. I guess I could install command line maven as well.... but is that sensible or will it just cause more problems?
Given these kind of issues, Is there a way to get maven-release-plugin to work smoothly within Eclipse, or should I just give up and continue to do releases manually?

I have been using release plugin, but only from command line.
Re. 1. The backup files that release plugin creates are needed if something goes wrong in time of preparing the release. You can always rollback the prepared release using release:rollback command. When you do release:perform they will be deleted.
Re. 2. The plugin changes the version number from snapshot version for example: 0.0.1-SNAPSHOT: to release version: 0.0.1. Then after release:perform release version is moved to the maven repository and release plugin changes version again to 0.0.2-SNAPSHOT. Now you can use you full released (tested) version in your testing or production enviornment and snapshot version for developping purposes.
Re. 3. I don't know what is causing the problem, but I don't see the problem by using release plugin from command line.

Also mvn 3.3.3 installs a mvn.cmd file, instead of a mvn.bat file in Windows.
You should copy mvn.cmd to mvn.bat

Well i know this link is OLD , but to help some on who reffers this link for the issue 3.
Install maven separately on to local Box and give the path of the installation under Windows->Preferences--> maven--> Installation. Also you have to define the same in the run configuration within the Eclipse.
Attached is a link that explains the same.
http://maven.40175.n5.nabble.com/Build-Failure-prepare-release-td510949.html

You might be able to overcome the error you mention by installing command line Maven and configure Eclipse to use that rather than the embedded one by choosing Window -> Preferences -> Maven -> Installations, but I agree with the advice of making your releases outside Eclipse.

Class Not Found Exception when running JUnit test

I am getting this error when running JUnit test in Eclipse:
Class not found com.myproject.server.MyTest
java.lang.ClassNotFoundException: com.myproject.server.MyTest
at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.loadClass(RemoteTestRunner.java:693)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.loadClasses(RemoteTestRunner.java:429)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:452)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
I've tried adding JUnit library in the classpath although I'm using maven, and the JUnit library is in the POM dependency.
I already have tried cleaning the project and created a new JUnit test case using the JUnit plugin for Eclipse, still getting the same error.

This appears to occur because only the source code is compiling when you use mvn clean compile (I'm using maven 3.1.0 so I'm not sure if it always behaved like this).
If you run mvn test, the test code will compile as well, but then it runs the tests (which may not be immediately desirable if you're trying to run them through Eclipse.) The way around this is to add test-compile to your Maven command sequence whenever you do a mvn clean. For example, you would run mvn clean compile test-compile.

I had a similar problem with my tests and found somewhere in the Web, that you have to go to Build Path in your project's properties and move Maven Dependencies above JRE System Library. That seems to have worked for me.

I faced the same problem and I was able to fix it using #slomek's answer but the issue resurfaced after that.
I finally fixed it by adding my project's output folder to the JUnit test's run configuration. Steps are:
Find your project's output folder from Project properties -> Java Build Path -> Default output folder
Usually this is <project-folder>/bin
Go to Run -> Run Configurations...
Click on the unit test's run configuration and click on the Classpath tab
Explicitly add your project's output folder under User Entries - even if the project is already included there
Click on Advanced -> Add folder to add the output folder
This issue might be due to weird project setup in Eclipse - e.g. source folder with nested maven projects imported as a single project/folder (at least that was how my project was setup).

If this problem occurs in Eclipse only, executing command Project -> Clean... on selected project may help.

After having tried everything here with no improvement, I solved my issue by just restarting Eclipse

I fixed my issue by running maven update.
Right click project your project > Maven > Update Project

In my case I had a wrong maven directory structure.
Which should be like:
/src/test/java/ com.myproject.server.MyTest
After I fixed that - everything worked like a charm.

In my case, only next steps helped me to resolve this issue:
Project->properties->Run/Debug Settings.
In "Launch configurations for '.....'" select classes/projects
Edit -> Classpath -> "Restore Default Entries"

I had the similar problem with my Eclipse Helios which debugging Junits. My problem was little different as i was able to run Junits successfully but when i was getting ClassNotFoundException while debugging the same JUNITs.
I have tried all sort of different solutions available in Stackoverflow.com and forums elsewhere, but nothing seem to work. After banging my head with these issue for close to two days, finally i figured out the solution to it.
If none of the solutions seem to work, just delete the .metadata folder created in your workspace. This would create an additional overhead of importing the projects and all sorts of configuration you have done, but these will surely solve these issue.
Hope these helps.

Earlier, in this case, I always did mvn eclipse:eclipse and restarted my Eclipse and it worked. After migrating to GIT, it stopped working for me which is somewhat weird.
Basic problem here is Mr Eclipse does not find the compiled class.
Then, I set the output folder as Project/target/test-classes which is by default generated by mvn clean install without skipping the test and proceeded with following workaround:
Option 1: Set classpath for each test case
Eclipse ->Run ->Run Configurations ->under JUnit->select mytest -> under classpath tab->Select User Entries->Advanced->Add Folder -> Select ->Apply->Run
Option 2: Create classpath variable and include it in classpath for all the test cases
Eclipse ->Windows ->Classpath Variables ->New->[Name : Junit_test_cases_cp | path : ]->ok
Then go to
Eclipse->Run ->Run Configurations ->JUnit->select mytest ->under classpath tab ->Select User Entries->Advanced->Add classpath variables->Select Junit_test_cases_cp->ok->Apply->Run
This is the only thing currently working for me after trying all the suggestions online.

NoClassDefFoundError really means it can't initilize the class. It has nothing to do with finding the class. I got this error when calling trim() on a null String.
JUnit won't show NullPointerException. The string isn't null when running normally because
I'm fetching the string from a properties file which is not availible for tests.
My advice is to remove pieces from the class until your tests start passing. Then you can determine which line is giving the error.

In my case, changing the order of Maven Dependencies from Build Path configuration did not work for me. I changed its order from Run configuration.
Follow these steps:
• Go to Run -> Run Configurations...
• Click on the unit test's run configuration and click on the Classpath tab.
• check Use temporary JAR to specify classpath (to avoid classpath length limitations).
May be it is enough and your test works. You should try, so press Run button. If it did not work. Follow all previous steps again and without pressing Run button, go to the next step.
• In sub branches of User Entries move Maven Dependencies above your project or test class.
• Click Run button.

These steps worked for me.
Delete the content of local Maven repository.
run mvn clean install in the command line. (cd to the pom directory).
Build Project in Eclipse.

1- mvn eclipse:eclipse
2- project clean all projects
3- restart

It's worth mentioning as another answer that if you're using eGit, and your classpath gets updated because of say, a test coverage tool like Clover, that sometimes there's a cleanup hiccup that does not completely delete the contents of /path/to/git/repository/<project name>/bin/
Essentially, I used Eclipse's Error Log View, identified what was causing issues during this cleanup effort, navigated to the source directory, and manually deleted the <project name>/bin directory. Once that finished I went back to Eclipse and refreshed (F5) my project and the error went away.

It can also be due to "[ERROR] No compiler is provided in this environment. Perhaps you are running on a JRE rather than a JDK?"

I had the same problem with a Gradle project with a test SourceSet with two resource directories.
This snippet comes from a main-module.gradle and adds a resource dir to the test SourceSet:
sourceSets {
test {
resources {
srcDir('../other-module/src/test/resources')
}
}
}
Doing this I had two resource directories related to the test SourceSet of the project main-module:
../other-module/src/test/resources
src/test/resources (relative to the main-module folder, automatically added by the java plugin)
I find out that if I had two files with the same name in both the source directories, something in the process resources stage went wrong. As result, no compilation started and for this reason no .class were copied in the bin directory, where JUnit was looking for the classes. The ClassNotFoundException disappeared just renaming one of the two files.

It seems compile issue. Run project as Maven test, then Run as JUnit Test.

For project that does not use maven : This worked for me https://ihategeek.wordpress.com/2012/04/18/eclipse-junit-test-class-not-found/
Adding the jre and project src at the bottom in Order and exports in build path

Pls check if you have added junit4 as dependency.
e.g
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>

For me I had to put the project x/src/test/java/ at the bottom of the "order and export" in the "java build path"

Check if your project is opened as a Maven project and not just a regular Java project. Actually a no-brainer, but that is exactly the same reason why you might miss it.

I had faced the same issue. I solved it by removing the external JUnit jar dependency which I added by download from the internet externally. But then I went to project->properties->build path->add library->junit->choosed the version(ex junit4)->apply.
It automatically added the dependency. it solved my issue.

Making some dummy change and saving the test class can solve the problem. It will build the .class automatically

Might be you forgotten to place the Main class and Test Case class in
/src/test/java. Check it Once.

Problem loading resources while running in Eclipse

I'm working on a swing project, using maven2 (from command-line) and eclipse (without maven integration). So, I generate the eclipse project through maven eclipse plugin (mvn eclipse:eclipse), import it inside eclipse, and do all my work.
My problem is: when I run my app in eclipse (as a Java Application), I can't find none of the resources that are in my src directory. Digging for information on my problem, I get into this answer from another question. So, I compared the output from the following instructions:
MyClass.class.getResource("/").getPath();
MyClass.class.getProtectionDomain().getCodeSource().getLocation().toString();
Those gave me the following outputs, respectively:
${workspace_loc}/${my_project}/target/test-classes/
file:/${workspace_loc}/${my_project}/target/classes/
Checking the above locations, I could see that the former is empty, while the other one contained all my compiled classes and resources. So, I came to the conclusion that the classloader is looking for my resources in the wrong place. So, I think I have three questions:
Is my understanding correct?
If so, how it does to find the classes it is loading?
How do I solve this?
UPDATE: I've changed my code, so instead of invoking MyClass.class.getResource(...) or MyClass.class.getResourceAsStream(...), I'm now using ClassLoader.getSystemResource(...) and ClassLoader.getSystemResourceAsStream(...). In this way, everything is working fine in eclipse. I just don't know exactly why. Any hint on this?

Two possibles cases for me :
You are using eclipse to compile your project. Then eclipse is configured to exclude (or not include) resources in the src folder. You can set it in Project/Properties/Java Build Path/Source. Then you expend your src folder, and ensure you have something like "Included All", "Excluded None".
You run your maven application using maven to compile and not eclipse, even though you are using eclipse as your IDE. Then by default maven will not copy resources from the source folder to the output folder... Because it is not the standard maven way of doing things. Thus the resource are missing from the classpath and you don't find them. Just change your maven configuration to also include resources from your source folder.

I think you have to add src/main/resources to the build path. This is done in Project Properties > Build Path > Source. Here is how the standard maven project looks:
In future when using Eclipse I suggest to use m2eclipse plugin and create project using it. This will automatically make sure that all these folders are in the build path.

Try this:
Run configurations... -> Classpath -> User Entries -> Advanced... -> Add Folders

Can you try loading the resources using below?
this.getClass().getClassLoader().getResourceAsStream(propertyFileName)

This might be useful information
Eclipse Maven plugin has its own Classpath Container that conflicts with generated class paths when enabled.

What I would suggest is stop using eclipse:eclipse (sorry - harsh I know). I used it for about 8 months, cant believe it took me that long, and used M2Eclipse. M2Eclipse is an eclipse plugin in which you do the following.
Enable Dependency Management.
Update Project Configuration
(In Eclipse) Project -> Build Project
(In Eclipse) Run Application
It may not seem it, but its a much easier and less frustrating way of doing it.
Before, with eclipse:eclipse. You would have to run it then hit refresh and hope that everything is configured - if you have a multi-module pom things can really go wrong.

For me the Files within the WEB-INF were not getting included. Hence I added them to Buildpath (Project -> Build Path -> Configure Build Path -> Add folder (project/src/main/webapp). This resolved the issue.