Develop Reference

Unable to initialize main class selenium.Test [duplicate]

I have added the most updated Selenium dependency in my pom.xml
<dependency>
<groupId>org.seleniumhq.selenium</groupId>
<artifactId>selenium-java</artifactId>
<version>3.7.1</version>
</dependency>
I ran
mvn clean install
inside the directory with my pom.xml and I have also imported the correct classes in my app class as per the Selenium documentation
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.firefox.FirefoxDriver;
However when i try and run my main method, I get the following error
Exception in thread "main" java.lang.NoClassDefFoundError:
org/openqa/selenium/WebDriver
I look in my ~/.m2/repository folder and I don't see an openqa folder but instead I see a seleniumhq folder.
Why didn't maven install the openqa folder, and why does the documentation say to import from org.openqa... when that never exist in my jar repository. I'm very confused, I just want to be able to import selenium Webdriver successfully while having it in my local repository.

Firstly, check properly if you have all important dependencies for your program.
Secondly, I had similar error while running maven project:
Caused by: java.lang.NoClassDefFoundError: org/openqa/selenium/JavascriptExecutor
And this problem was because of inappropriate plugin, because I tested different versions of Selenium and it didn't help me.
So when I changed maven-jar-plugin:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>3.1.0</version>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<classpathPrefix>lib/</classpathPrefix>
<mainClass>your_main_class</mainClass>
</manifest>
</archive>
</configuration>
</plugin>
to maven-shade-plugin plugin:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<version>3.0.0</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
<configuration>
<transformers>
<transformer
implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
<mainClass>your_main_class</mainClass>
</transformer>
</transformers>
</configuration>
</execution>
</executions>
</plugin>
The issue was gone.
The difference between plugins you can find here.
In addition, sometimes we upgrade our libraries even with same method name. Due this different in version, we get NoClassDefFoundError or NoSuchMethodError at runtime when one library was not compatible with such an upgrade.
Java build tools and IDEs can also produce dependency reports that tell you which libraries depend on that JAR. Mostly, identifying and upgrading the library that depends on the older JAR resolve the issue.
To summarize:
try to change versions of Selenium, if it contains all dependencies;
try to add necessary dependencies if you don't have it;
try to check folder of maven if it has or not what says specific error;
try to play with plugins if nothing helps above.

NoClassDefFoundError
NoClassDefFoundError in Java occurs when Java Virtual Machine is not able to find a particular class at runtime which was available at compile time. For example, if we have resolved a method call from a class or accessing any static member of a Class and that Class is not available during run-time then JVM will throw NoClassDefFoundError.
The error you are seeing is :
Exception in thread "main" java.lang.NoClassDefFoundError:
org/openqa/selenium/WebDriver
This clearly indicates that Selenium is trying to resolve the particular class at runtime from org/openqa/selenium/WebDriver which is no more available.
As you mentioned of looking into ~/.m2/repository folder, the maven folder structure for Selenium v3.7.1 (on Windows) is as follows :
C:\Users\<user_name>\.m2\repository\org\seleniumhq\selenium\selenium-java\3.7.1
So when you see a seleniumhq folder, it is pretty much expected.
What went wrong :
From all the above mentioned points it's clear that the related Class or Methods were resolved from one source Compile Time which was not available during Run Time.
This situation occurs if there are presence of multiple sources to resolve the Classes and Methods through JDK / Maven / Gradle.
Solution :
Here are a few steps to solve NoClassDefFoundError :
While using a Build Tool e.g. Maven or Gradle, remove all the External JARs from the Java Build Path. Maven or Gradle will download and resolve all the required dependencies.
If using Selenium JARs within a Java Project add only required External JARs within the Java Build Path and remove the unused one.
While using Maven, either use <artifactId>selenium-java</artifactId> or <artifactId>selenium-server</artifactId>. Avoid using both at the same time.
Remove the unwanted other <dependency> from pom.xml
Clean you Project Workspac within your IDE periodically only to build your project with required dependencies.
Use CCleane tool to wipe away the OS chores periodically.
While you execute a Maven Project always do maven clean, maven install and then maven test.

Encountered this error in Eclipse IDE. In Eclipse go to Project properties and in Java Build Path just add selenium jars in Classpath instead of Modulepath. Then under the Project tab on the top do a Clean to remove earlier buiid and then do a Run.

Are you using an IDE or working from command line? In Eclipse for example you can force downloading all dependencies by right clicking on your project, going to Maven menu item and then selecting Update Project. Then check the "Force Update of Snapshots/Releases" checkbox.
If you are opening from command line do:
mvn clean install -U
from your project path.

This is happening because you are selecting jar files under modulepath, you should add them under class path.

org.openqa.selenium is the package in the selenium-api-{version}.jar under the seleniumhq\selenium\selenium-api folder.
org.openqa.selenium.firefox is the package in the selenium-firefox-driver-{version}.jar under the seleniumhq\selenium\selenium-firefox-driver folder.
So there is no openqa folder, it's just the package name under the seleniumhq folder, you should have a check into these jar.
It's hard to say what caused NoClassDefFoundError exception without project structure and code detail. The exception is not the same as ClassNotFoundException. Maybe this answer https://stackoverflow.com/a/5756989/5374508 would be helpful.

What worked for me was to add this dependency to pom.xml:
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>25.0-jre</version>
</dependency>

I was getting below error from past 2 days and what helped me was to remove all the selenium extra dependencies like selenium-support, selenium-chrome-driver etc and only keeping the below dependencies in POM file.
Error:-
java.lang.NoClassDefFoundError: org/openqa/selenium/HasAuthentication
at java.base/java.lang.ClassLoader.defineClass1(Native Method)
at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1012)
at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:150)
at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:862)
at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:760)
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:681)
Dependencies in the pom file after removing all other:-
<dependencies>
<dependency>
<groupId>org.seleniumhq.selenium</groupId>
<artifactId>selenium-java</artifactId>
<version>4.1.1</version>
</dependency>
<dependency>
<groupId>org.testng</groupId>
<artifactId>testng</artifactId>
<version>7.4.0</version>
<scope>test</scope>
</dependency>
</dependencies>

Have encountered this issue while running selenium test in eclipse IDE.
Navigate to following path:
1.Properties >> Java build path >> Libraries.
2.Add all selenium jars in Classpath instead of Modulepath.
3.Apply and close modal.
4.Now go to build path and click on "Configure Build Path".
5.Now run the selenium test.

Failed to execute goal errors when running mvn install:install-file [duplicate]

I am new to Maven and trying to setup my first project in Maven but receiving the below error message when I am doing " Run as -> Maven install " in Eclipse. Below is my settings.xml and pom.xml
Settings.xml
<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0
https://maven.apache.org/xsd/settings-1.0.0.xsd">
<localRepository>C:\Users\Iam\.m2\repository</localRepository>
<profiles>
<profile>
<repositories>
<repository>
<id>central</id>
<url>http://central.maven.org/maven2/</url>
</repository>
</repositories>
<pluginRepositories>
</pluginRepositories>
</profile>
</profiles>
</settings>
POM.XML
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.mytest</groupId>
<artifactId>MySpringBootMaven</artifactId>
<packaging>war</packaging>
<version>0.0.1-SNAPSHOT</version>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.11.RELEASE</version>
</parent>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>2.5</version><!--$NO-MVN-MAN-VER$-->
<configuration>
<warnName>Test.war</warnName>
</configuration>
</plugin>
</plugins>
</build>
</project>
Error message:
at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
Caused by: org.eclipse.aether.resolution.ArtifactDescriptorException: Failed to read artifact descriptor for org.springframework.boot:spring-boot-maven-plugin:jar:1.5.11.RELEASE
at org.apache.maven.repository.internal.DefaultArtifactDescriptorReader.loadPom(DefaultArtifactDescriptorReader.java:302)
at org.apache.maven.repository.internal.DefaultArtifactDescriptorReader.readArtifactDescriptor(DefaultArtifactDescriptorReader.java:218)
at org.eclipse.aether.internal.impl.DefaultRepositorySystem.readArtifactDescriptor(DefaultRepositorySystem.java:287)
at org.apache.maven.plugin.internal.DefaultPluginDependenciesResolver.resolve(DefaultPluginDependenciesResolver.java:103)
... 27 more
Caused by: org.eclipse.aether.resolution.ArtifactResolutionException: Could not transfer artifact org.springframework.boot:spring-boot-maven-plugin:pom:1.5.11.RELEASE from/to central (https://repo.maven.apache.org/maven2): Received fatal alert: protocol_version
at org.eclipse.aether.internal.impl.DefaultArtifactResolver.resolve(DefaultArtifactResolver.java:444)
at org.eclipse.aether.internal.impl.DefaultArtifactResolver.resolveArtifacts(DefaultArtifactResolver.java:246)
at org.eclipse.aether.internal.impl.DefaultArtifactResolver.resolveArtifact(DefaultArtifactResolver.java:223)
at org.apache.maven.repository.internal.DefaultArtifactDescriptorReader.loadPom(DefaultArtifactDescriptorReader.java:287)
... 30 more
Caused by: org.eclipse.aether.transfer.ArtifactTransferException: Could not transfer artifact org.springframework.boot:spring-boot-maven-plugin:pom:1.5.11.RELEASE from/to central (https://repo.maven.apache.org/maven2): Received fatal alert: protocol_version
How to resolve the Received fatal alert: protocol_version ? My java version is 1.7 and maven version is 3.3.3

Sonatype no longer supports TLSv1.1 and below (effective, June 18th, 2018). My guess is that you are using TLSv1.1 protocol or below.
The documentation I listed gives you 4 options:
Upgrade your Java runtime, for example with OpenJDK builds or Oracle paying support
Configure your Java runtime to enable TLS 1.2 by adding -Dhttps.protocols=TLSv1.2
Use a repository manager that uses a Java version supporting TLS 1.2
Revert back to http until you can acheive one of the above remediation steps.
I fixed it myself by just using -Dhttps.protocols=TLSv1.2 as a VM argument.
 

For a permanent solution(mostly required in Java 7) - in you build directory(where you do the mvn command from) add directory:
.mvn (in cmd mkdir .mvn)
and in it create file
jvm.config
and in put the following line:
-Dhttps.protocols=TLSv1.2

The simplest solution is to configure your JVM runtime arguments. On eclipse, you can do it as following :
go to windows>preferences>java>installed JREs
click on the Intalled JRE/JDK you are using for your project
click on "edit" on le right,
and add -Dhttps.protocols=TLSv1.2 in the Default VM arguments Input field.
see the screenshot :

The Package you are trying to install doesn't support TLS1.1 and you might be by default using TLS 1.1. Configure your Java runtime to enable TLS 1.2 by adding -Dhttps.protocols=TLSv1.2 to your Maven Build command would solve the problem.
For Example: mvn clean install -Dhttps.protocols=TLSv1.2

I had upgraded from Java 1.7 to Java 1.8 and got the same error.
To resolve this error, I checked the mvn version using mvn -version and found that JAVA_HOME was still using the Java 1.7. I changed the JAVA_HOME in the environment variable to point to Java 1.8 jre in JDK
Hope this helps someone.

I set my settings.xml file in the .m2 directory just as the one here: https://github.com/alipay/sofa-rpc/pull/190/files
Then exec mvn install and all dependencies started to download. I haven't had a settings.xml file before and I am not using any proxy.
Hope it helps somebody.
PD. I have jdk 1.7 and Maven 3.3.9

I resolved this error in SpringToolSuit by adding settings.xml file in .m2 folder which is located in Users folder of C drive and by updating Project by
right click on pom.xml -> Maeven -> Update Project.
Make sure you select Force update of snapshots/releases.

It needs both : Configuring the JVM runtime arguments as well as having a settings.xml, after I did both it worked. Updating only the JVM runtime argument did not help.

In my case the automatic update of maven dependencies were disabled in eclipse.
Solution:
Go to
Windows->Preferences->Maven
and uncheck the check box
"Do not automatically update dependencies from remote repositories"
Then update the project
Right click on project->maven->update project

I had the same issue, I tried most of the answers here but still did not work. My issue was Proxy settings on my IDE. So it is also important to remember to check proxy settings. File > Settings > System Settings > HTTP Proxy - Select Auto-Detect proxy settings

On my new laptop (Win10) I have downgraded maven 3.8.7->3.6.3 and jdk 19->1.8
Maven 3.8.7 is blocking a lot of old repositories, one sometimes does need.

Exception in thread "main" java.lang.NoClassDefFoundError: org/openqa/selenium/WebDriver

I have added the most updated Selenium dependency in my pom.xml
<dependency>
<groupId>org.seleniumhq.selenium</groupId>
<artifactId>selenium-java</artifactId>
<version>3.7.1</version>
</dependency>
I ran
mvn clean install
inside the directory with my pom.xml and I have also imported the correct classes in my app class as per the Selenium documentation
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.firefox.FirefoxDriver;
However when i try and run my main method, I get the following error
Exception in thread "main" java.lang.NoClassDefFoundError:
org/openqa/selenium/WebDriver
I look in my ~/.m2/repository folder and I don't see an openqa folder but instead I see a seleniumhq folder.
Why didn't maven install the openqa folder, and why does the documentation say to import from org.openqa... when that never exist in my jar repository. I'm very confused, I just want to be able to import selenium Webdriver successfully while having it in my local repository.

Firstly, check properly if you have all important dependencies for your program.
Secondly, I had similar error while running maven project:
Caused by: java.lang.NoClassDefFoundError: org/openqa/selenium/JavascriptExecutor
And this problem was because of inappropriate plugin, because I tested different versions of Selenium and it didn't help me.
So when I changed maven-jar-plugin:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>3.1.0</version>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<classpathPrefix>lib/</classpathPrefix>
<mainClass>your_main_class</mainClass>
</manifest>
</archive>
</configuration>
</plugin>
to maven-shade-plugin plugin:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<version>3.0.0</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
<configuration>
<transformers>
<transformer
implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
<mainClass>your_main_class</mainClass>
</transformer>
</transformers>
</configuration>
</execution>
</executions>
</plugin>
The issue was gone.
The difference between plugins you can find here.
In addition, sometimes we upgrade our libraries even with same method name. Due this different in version, we get NoClassDefFoundError or NoSuchMethodError at runtime when one library was not compatible with such an upgrade.
Java build tools and IDEs can also produce dependency reports that tell you which libraries depend on that JAR. Mostly, identifying and upgrading the library that depends on the older JAR resolve the issue.
To summarize:
try to change versions of Selenium, if it contains all dependencies;
try to add necessary dependencies if you don't have it;
try to check folder of maven if it has or not what says specific error;
try to play with plugins if nothing helps above.

NoClassDefFoundError
NoClassDefFoundError in Java occurs when Java Virtual Machine is not able to find a particular class at runtime which was available at compile time. For example, if we have resolved a method call from a class or accessing any static member of a Class and that Class is not available during run-time then JVM will throw NoClassDefFoundError.
The error you are seeing is :
Exception in thread "main" java.lang.NoClassDefFoundError:
org/openqa/selenium/WebDriver
This clearly indicates that Selenium is trying to resolve the particular class at runtime from org/openqa/selenium/WebDriver which is no more available.
As you mentioned of looking into ~/.m2/repository folder, the maven folder structure for Selenium v3.7.1 (on Windows) is as follows :
C:\Users\<user_name>\.m2\repository\org\seleniumhq\selenium\selenium-java\3.7.1
So when you see a seleniumhq folder, it is pretty much expected.
What went wrong :
From all the above mentioned points it's clear that the related Class or Methods were resolved from one source Compile Time which was not available during Run Time.
This situation occurs if there are presence of multiple sources to resolve the Classes and Methods through JDK / Maven / Gradle.
Solution :
Here are a few steps to solve NoClassDefFoundError :
While using a Build Tool e.g. Maven or Gradle, remove all the External JARs from the Java Build Path. Maven or Gradle will download and resolve all the required dependencies.
If using Selenium JARs within a Java Project add only required External JARs within the Java Build Path and remove the unused one.
While using Maven, either use <artifactId>selenium-java</artifactId> or <artifactId>selenium-server</artifactId>. Avoid using both at the same time.
Remove the unwanted other <dependency> from pom.xml
Clean you Project Workspac within your IDE periodically only to build your project with required dependencies.
Use CCleane tool to wipe away the OS chores periodically.
While you execute a Maven Project always do maven clean, maven install and then maven test.

Encountered this error in Eclipse IDE. In Eclipse go to Project properties and in Java Build Path just add selenium jars in Classpath instead of Modulepath. Then under the Project tab on the top do a Clean to remove earlier buiid and then do a Run.

Are you using an IDE or working from command line? In Eclipse for example you can force downloading all dependencies by right clicking on your project, going to Maven menu item and then selecting Update Project. Then check the "Force Update of Snapshots/Releases" checkbox.
If you are opening from command line do:
mvn clean install -U
from your project path.

This is happening because you are selecting jar files under modulepath, you should add them under class path.

org.openqa.selenium is the package in the selenium-api-{version}.jar under the seleniumhq\selenium\selenium-api folder.
org.openqa.selenium.firefox is the package in the selenium-firefox-driver-{version}.jar under the seleniumhq\selenium\selenium-firefox-driver folder.
So there is no openqa folder, it's just the package name under the seleniumhq folder, you should have a check into these jar.
It's hard to say what caused NoClassDefFoundError exception without project structure and code detail. The exception is not the same as ClassNotFoundException. Maybe this answer https://stackoverflow.com/a/5756989/5374508 would be helpful.

What worked for me was to add this dependency to pom.xml:
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>25.0-jre</version>
</dependency>

I was getting below error from past 2 days and what helped me was to remove all the selenium extra dependencies like selenium-support, selenium-chrome-driver etc and only keeping the below dependencies in POM file.
Error:-
java.lang.NoClassDefFoundError: org/openqa/selenium/HasAuthentication
at java.base/java.lang.ClassLoader.defineClass1(Native Method)
at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1012)
at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:150)
at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:862)
at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:760)
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:681)
Dependencies in the pom file after removing all other:-
<dependencies>
<dependency>
<groupId>org.seleniumhq.selenium</groupId>
<artifactId>selenium-java</artifactId>
<version>4.1.1</version>
</dependency>
<dependency>
<groupId>org.testng</groupId>
<artifactId>testng</artifactId>
<version>7.4.0</version>
<scope>test</scope>
</dependency>
</dependencies>

Have encountered this issue while running selenium test in eclipse IDE.
Navigate to following path:
1.Properties >> Java build path >> Libraries.
2.Add all selenium jars in Classpath instead of Modulepath.
3.Apply and close modal.
4.Now go to build path and click on "Configure Build Path".
5.Now run the selenium test.

Running jar built using Maven causes "java.lang.NoClassDefFoundError: org/rosuda/JRI/Rengine" error

I am trying to build a JAR library that can invoke R code.
I basically want this jar to be capable enough to be able to run on any machine that has support for running jar executables(No need of seperate R software).
For this I am using Maven. I am able to compile and create a jar without any errors. However, when I run it, I am unable to yield successful results.
This is my java code
package com.company.analytics.timeseries;
import org.rosuda.JRI.REXP;
import org.rosuda.JRI.Rengine;
public class App {
public static void main(String[] args) {
System.out.println("Creating Rengine (with arguments)");
String[] Rargs = { "--vanilla" };
Rengine re = new Rengine(Rargs, false, null);
System.out.println("Rengine created, waiting for R");
if (!re.waitForR()) {
System.out.println("Cannot load R");
return;
}
System.out.println("Done.");
}
}
This is my pom.xml file
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.company.analytics</groupId>
<artifactId>timeseries</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>timeseries</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.nuiton.thirdparty</groupId>
<artifactId>JRI</artifactId>
<version>RELEASE</version>
</dependency>
<dependency>
<groupId>org.rosuda.REngine</groupId>
<artifactId>REngine</artifactId>
<version>2.1.0</version>
</dependency>
</dependencies>
<repositories>
<repository>
<id>central</id>
<name>Maven Central</name>
<url>http://repo1.maven.org/maven2</url>
</repository>
</repositories>
</project>
I used mvn clean and then mvn package to create the jar file.
A JAR file of 4KB is created in C:\MVN\project\analytics\timeseries\target. Thern, from the command line on Windows, when I run execute this jar file, I get the following error
C:\MVN\project\analytics\timeseries\target\classes>java com.company.analytics.timeseries.App
Creating Rengine (with arguments)
Exception in thread "main" java.lang.NoClassDefFoundError: org/rosuda/JRI/Rengine
at com.company.analytics.timeseries.App.main(App.java:10)
Caused by: java.lang.ClassNotFoundException: org.rosuda.JRI.Rengine
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 1 more
I am trying to figure out what mistake am I committing. I tried to find answers by googling, but I couldn't fix it.

Since I've been smashing my head against this for a day now and I'll likely forget in the future and reference this page - per what Gergely Basco's suggests in an above comment, strictly speaking both R and rJava need to be installed on the machine in order to resolve the Cannot find JRI native library! issue when instantiating your org.rosuda.REngine.REngine object, and this cannot be done exclusively by way of adding the JRIEngine dependency in your pom.xml (bummer).
Steps (for how I'm doing it anyway for my later image):
Install Brew (I just happen to be using Brew for other dependencies)
/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
Install R using brew:
brew tap homebrew/science
brew install R
Install rJava with R (takes a bit of compile time, grab a coffee)
install.packages("rJava")
add rJava/jri to java.library.path classpath, add R_HOME to environment variables (where you installed R - in my case, where Brew installed it). Note that if you're trying to run this in your IDE(I'm running IDEA16), it won't inherit the path you set in ~/.bash_profile, you need to set it in your run configuration.
-Djava.library.path="/usr/local/lib/R/3.3/site-library/rJava/jri/
R_HOME=/usr/local/Cellar/r/3.3.1_2/R.framework/Resources
Ensure maven has dependency for JRIEngine in pom.xml
<dependency>
<groupId>com.github.lucarosellini.rJava</groupId>
<artifactId>JRIEngine</artifactId>
<version>0.9-7</version>
</dependency>
Instantiate REngine (I need this version in order to pass dataframe to R from java)
String[] Args = {"--vanilla"};
REngine engine = REngine.engineForClass("org.rosuda.REngine.JRI.JRIEngine", Args, new REngineStdOutput (), false);
What you should end up with looks something like this at runtime, if you instantiate with the callback argument (new REngineStdOutput () ); otherwise if you just instantiate with the String engineForClass("org.rosuda.REngine.JRI.JRIEngine"), you'll wont get the below output from R on startup/elsewise, depending on if you want it or not:
/**R version 3.3.1 (2016-06-21) -- "Bug in Your Hair"
Copyright (C) 2016 The R Foundation for Statistical Computing
Platform: x86_64-apple-darwin15.5.0 (64-bit)
R is free software and comes with ABSOLUTELY NO WARRANTY.
You are welcome to redistribute it under certain conditions.
Type 'license()' or 'licence()' for distribution details.
Natural language support but running in an English locale
R is a collaborative project with many contributors.
Type 'contributors()' for more information and
'citation()' on how to cite R or R packages in publications.
Type 'demo()' for some demos, 'help()' for on-line help, or
'help.start()' for an HTML browser interface to help.
Type 'q()' to quit R.**/
Hope this helps someone in the future and saves them from the pain.

You need to build a jar with all your dependencies included. (aka fat jar) Since you are already using Maven, the only thing you need to do is to instruct Maven to include the dependencies by adding this plugin to your pom.xml file:
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<version>2.5.5</version>
<configuration>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
<executions>
<execution>
<id>assemble-all</id>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>

You are missing the classpath argument. Your jar file contains your compiled code without any 3rd party jars. When you want to run it, you should add -cp and point to all your 3rd party jars.
You can also build a single jar with all dependencies using Maven's assembly plugin.

Maven project giving error

After setting up the project in intellij as a maven project like so ..
I set up my pom.xml file with a basic structure ...
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.yourcompany.test</groupId>
<artifactId>jreddit-testing</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>jar</packaging>
<name>jreddit-testing</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>com.github.jreddit</groupId>
<artifactId>jreddit</artifactId>
<version>1.0.2</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
</dependencies>
</project>
when I run sudo mvn clean install it installs everything with no errors.
On running the project I get the Error ..
Error:java: directory not found:
/Users/stingRay/Documents/workspace/jreddit/target/generated-sources/annotations

Not sure if this will solve your issue but the comments have not enough space :)
I would argue the environment variables are simply not properly configured. I recommend not using sudo and maven. It is simply not necessary if everything is configured properly.
The download page of maven contains the instructions what to do: http://maven.apache.org/download.cgi (scrolling down)
In short:
Download the Java Development Kit (I don't use the packet manager from Linux for this, to prevent having root being able to execute Java commands or run servers accidentally). It looks you are working on MacOS? So Download the dmg file from oracle.
Download the Maven archive and extract it (it can also be in a shared dirctory so it is readable for every user on the system)
the important part: setting the environment variables. You must set JAVA_HOME, M2_HOME, optionally MVN_OPTS and the PATH for convenience - so "mvn" runs in your terminal without sudo.
There are tutorials on the web that guide you through this, like this one: http://bitbybitblog.com/environment-variables-mac/
If you work with IntelliJ or the terminal the .bash_profile file be enough. Editing the .plist file is for OSX internal tools only. In IntelliJ it will work once the M2_HOME variable is set (if I remember correctly) and IntelliJ is restarted.
Note you may need to clean up the files already around (to make sure your user can write them without sudo). Meaning:
/Users/stingRay/Documents/workspace/jreddit/target/
/Users/stingRay/.m2/repository (or where your local maven repo is located)
Hope that will work :)