Develop Reference

Compilation error occurs if jars are added manually in Intellij

I am using Maven in my project, and for some reasons, some additional jars should be added manually (I have followed the step like Correct way to add external jars (lib/*.jar) to an IntelliJ IDEA project).
The package can be imported successfully. However, the compilation error happens, which indicates the package does not exist and cannot find the symbol of the used object.
I have tried the following tips but it remain unchanged:
Invalid caches / restarts
reimport
delete .idea file and .iml file
The scenario is quit similar to this one : https://intellij-support.jetbrains.com/hc/en-us/community/posts/206821195--beginner-question-including-external-jar-compile-error.
Please see the following sample images. It may run successfully but cannot be compiled well.

The reason is that when you add a library manually via IntelliJ, only IntelliJ knows about them and when you compile your code using Maven, it can't be find by Maven because Maven only searches for dependencies you defined in pom.xml.
You should install your libraries in your (at least) local maven repository and add them as a normal dependency in your pom.xml. Then you don't need to add them manually in IntelliJ.
You should follow the steps mentioned at Guide to installing 3rd party JARs
Update:
Also you should note that if you're working as a team, you should install this on the local maven repository of all developers (which is not practical). The best solution is to install a Maven repository (e.g. Nexus, Artifactory or Archiva) in a server on your local network and upload your private jar files on those servers. Then all developers can define the address of the local Maven repository server in their local Maven settings and use artifacts/libraries from that servers. Plus it works as a local cache/proxy to fetch any Maven artifacts and prevents unnecessary calls to public maven repositories.

java.lang.NoClassDefFoundError: org/apache/spark/streaming/api/java/JavaStreamingContext [duplicate]

I am getting ClassNotFoundException and NoClassDefFoundError exceptions when I attempt to run my application using a maven defined dependency.
I added my maven dependency for the jar in question to my pom.xml file with the following declaration:
<dependency>
<groupId>spy</groupId>
<artifactId>spymemcached</artifactId>
<version>2.8.4</version>
<scope>provided</scope>
</dependency>
This added the relevant JAR file to my Maven Dependencies folder in Eclipse. I can access the classes in code but I get the mentioned exceptions once I run the application.
The jar is referenced in my Java build path under Maven dependencies:
My local maven repository is added to my classpath:
When I attempt to run the application, I get the following two exceptions:
java.lang.NoClassDefFoundError: Lnet/spy/memcached/MemcachedClient;
java.lang.ClassNotFoundException: net.spy.memcached.MemcachedClient
Can anyone point me in the right direction?

Change provided to compile
Provided
This is much like compile, but indicates you expect the JDK or a container to provide the dependency at runtime. For example, when building a web application for the Java Enterprise Edition, you would set the dependency on the Servlet API and related Java EE APIs to scope provided because the web container provides those classes. This scope is only available on the compilation and test classpath, and is not transitive.

<scope>provided</scope>
"Provided" scope implies that the dependencies should be available only during compile phase and they will be available elsewhere during runtime and Maven shouldn't package them with the rest of the jars and classes of the current application.
Your dependency doesn't seem to be of "provided" scope. Remove that scope from your dependency definition and the jars will be present in your packaged jar/war/ear.

I was facing the same issue but i didn't have the tag defined on my POM, it was always working fine until one day all of a sudden started giving me that error in my local machine for no reason, the dependency was correctly set up in the POM and the jar was present in the local maven repository.
I tried cleaning the project and updating maven project but nothing, none of the other solutions suggested on other posts worked for me either.
I was finally able to solve it by going to the servers tab -> right click on Tomcat v8.0 -> browse deployment location
this should lead you to a temp folder like
.metadata.plugins\org.eclipse.wst.server.core\tmp1\wtpwebapps
then you browse to your project folder -> WEB-INF -> lib -> here i found out that the jar from the library that was giving the error was missing, so i just copied it from .m2\repository
Restarted the server and it started working as usual again.
I hope this helps some body facing the same issue.

Answer somewhat related to your problem, but still can help others.
Adding <scope>compile</scope> to the dependency was not enough in my case. I also had to add <packaging>jar</packaging> to the target module's pom.

I was also facing the same problem, after trying various solutions the issue was resolved by following steps...
click on server >open launch configurations >Arguments (copy
"LocalPath\temp0\wtpwebapps" path).
go to "LocalPath\temp0\wtpwebapps\ProjectName\WEB-INF\lib".
copy the JAR (which was causing ClassNotFoundException) from .m2 and place it in "LocalPath\temp0\wtpwebapps\ProjectName\WEB-INF\lib" path.

Eclipse detects wrong maven dependency

I faced with foggy issue.
I am novice in project. I use Eclipse. all my colleagues use IDEA. I have checkout project from svn.
I performed corresponding maven tasks for building and deploying project. all works good.
But my Eclipse shows me problem.
in code:
sceneService.uploadFile(...);
eclipse shows that sceneService hasn't uploadFile method
I began researching. I show this class on PC of my colleague. But there aren't this issue. I noticed that we use different version of jar file of sceneService class.
We use same revision of the pom.xml.
dependency for jar in my pom.xml(for my module):
<dependency>
<groupId>com.day.cq.dam</groupId>
<artifactId>cq-dam-scene7</artifactId>
<scope>provided</scope>
</dependency>
when I type alt+shift+w I see that jar contains sceneService class takes from another module.

I think there is some issue in downloading the correct jar by Maven. your local repository may contain an earlier version of the jar.
Try these commands by going to the root folder of your project from command prompt.
mvn eclipse:clean
mvn eclipse:eclipse
mvn install
if still the problem persists try deleting your local .m2 repository and again rebuilding the project

I think my earlier comments about the "provided" scope are a red herring. The actual problem is likely due to conflicting versions.
By default, Eclipse enables workspace resolution of artifacts. This means it will find artifacts to use (i.e. cq-dam-scene7) from other projects in your workspace. It will also find them in the .m2 repository as well; I'm not sure which takes precedence.
Possible routes towards a solution include:
Specify a version for your artifact. This will ensure you use the correct JAR, even if it has to be found in the local .m2 repository.
<dependency>
<groupId>com.day.cq.dam</groupId>
<artifactId>cq-dam-scene7</artifactId>
<version>1.2.3</version>
<scope>provided</scope>
</dependency>
Ensure your local cq-dam-scene7 project contains the correct code - i.e. a version with the uploadFile() method defined.

I am facing a similar issue, I have two Maven projects in workspace. Main Project is using output JAR of a Helper project as an artifact.
Now the problem is that Main project is trying to Reference JUnit library of Helper project (which has older version 4.10) instead of it's own JUnit library having version 4.12. Because of this in-correct referencing I get build errors in main project.
Only work around which I found is to close the Helper project and have only Main project open in workspace.
Possibly this is an Eclipse bug.

Delete the repository folder in .m2 (in your user dir) and let maven rebuild it in next build cycle.
It will ensure no old jars are cached locally

Created Simpl JAR file, imported to Maven project but Maven install is complainining "package does not exist"

I guess I haven't really had to do this much before because I am running into a strange issue. I am trying to generate a JAR from an existing Java project and then and putting it into a Spring Maven project. I'm sure I'm including it correctly, I have done this many times before with 3rd party JARs that I get (even though its a Maven project I have included some obscure JARs in it and put on buildpath, etc), with my JAR within Eclipse it is showing up fine as if its included, I have a test class that is importing a class from the JAR, instantiating it, etc and its not showing any errors (imports are fine in the IDE, etc), however when I go to do a Maven install I get:
[ERROR] /media/src/main/java/org/jadefalcon/automation/DataSetup/test.java:[11,15] package org.test does not exist
[ERROR] /media/src/main/java/org/jadefalcon/automation/DataSetup/test.java:[21,2] cannot find symbol
I have tried doing a Maven clean but still the same problem, the JAR class I am testing with is this: (was trying a more complex one but then tried this to troubleshoot the issue)
package org.test;
public class something {
public String main () {
return "it is definitely working fine";
}
}
Here is the JAR I generated (with sources visible):
https://docs.google.com/leaf?id=0BzB_xvrbRpbYODQyMjEzOWEtOTdjNS00YjM3LTlkZGUtNjY5NmIwN2RiNTRj&hl=en
I would appreciate any advice as I am rather perplexed and frustrated by this. Thanks

You can include a 'regular' jar in your maven project -just as you described- though it's not a best practice mainly because then you not even lose the functionality of Maven for that jar, but also the whole point of Maven dependency management: you will have to include that jar with your source to make it build.
You can of course also create a Maven artifact for that jar, build it with Maven, install it with Maven and use it as a normal Maven dependency.
You also can create a parent .pom and have your dependency project as a module in it and also your real application (or also your real app can be your parent). See further here.

Since this caused me quite a bit of grief, I figure I should post the solution I found. Apparently you aren't supposed to just include a regular lib JAR in a maven project (although I swear I have done it before and it worked), I found this way to include a local JAR that isn't form a repository from this post:
Can I add jars to maven 2 build classpath without installing them?
I did this and its doing the maven install properly (where version and artifactID are just made up value)
<dependency>
<groupId>org.test</groupId>
<artifactId>test</artifactId>
<version>1.0</version>
<scope>system</scope>
<systemPath>${basedir}/lib/testjar.jar</systemPath>
</dependency>

JAR in project-specific local Maven repo, how to see library in Eclipse project?

I've been trying to add a custom .jar (ftp://ftp.ncbi.nlm.nih.gov/pub/eutils/soap/v2.0/java/axis2_1.5.2_jdk_6.0.12/eutils_axis2.jar) to a project that doesn't have a central corporate maven repository and that instead will have the custom JARs checked into SCM in the project directory tree. I was following this post to make it happen: Maven: add a dependency to a jar by relative path (awesome post btw).
What I did was:
Add local repository to pom.xml
install the file into the local repository
Add dependency to pom.xml
Based on what I see in m2eclipse, the library has been successfully recognized by Maven and added to the dependency list (or it'd be called ? : ? or something similar)
The problem is that Eclipse still doesn't see the referenced lib, so this still fails:
import gov.nih.nlm.ncbi.www.soap.eutils.*;
Pardon my maven newbiness, but what are changes / next steps I need to make to get to:
Have Eclipse see the library so that autocomplete works (and the import can be resolved)
Be able to compile the project
Be able to execute the jar produced by mvn package?
Thanks!

If you see the JAR under "Maven Dependencies" in your project, Eclipse should be able to see and use it. If it's not there, then m2eclipse wasn't able to resolve the dependency properly.
If it is missing, m2eclipse was unable to download the dependency from your local repository for some reason. Check the Maven 2 Console for errors and the Problem View.
Lastly, the JAR itself might be corrupt. Maven doesn't check for that, it simply adds the file to the classpath. If Eclipse can't open the JAR, you can also get the errors you mentioned.