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

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.

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.

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.