Java Maven project cannot find dependency

Question

Whenever I try to run my project as maven install, it creates a completely normal jar file. It is a swing gui application. However, when I click a button in the GUI that uses this websocket client, it ouputs the error below.

Exception in thread "Thread-2" java.lang.NoClassDefFoundError: com/neovisionaries/ws/client/WebSocketException
    at bot.BotFunc.run(BotFunc.java:30)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.ClassNotFoundException: com.neovisionaries.ws.client.WebSocketException
    at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:352)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
    ... 2 more

my pom.xml looks like this:

<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>HelixBot</groupId>
  <artifactId>HelixBot</artifactId>
  <version>1.1</version>
  <build>
    <sourceDirectory>src</sourceDirectory>
    <plugins>
      <plugin>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.8.1</version>
        <configuration>
          <source>1.8</source>
          <target>1.8</target>
        </configuration>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-jar-plugin</artifactId>
        <version>3.2.0</version>
        <configuration>
          <archive>
            <manifest>
              <mainClass>gui.GUIMain</mainClass>
            </manifest>
          </archive>
        </configuration>
      </plugin>
    </plugins>
  </build>
  <dependencies>
  <dependency>
    <groupId>com.neovisionaries</groupId>
    <artifactId>nv-websocket-client</artifactId>
    <version>2.14</version>
  </dependency>
  </dependencies>
  <packaging>jar</packaging>
</project>

As you can see, the correct dependency is added, so I am not sure why this error is appearing. I have tried clean building it and checked the .project and .classpath files. It may be due to the fact that I converted it to maven from a regular java project, but I have not found anything. Please let me know if there is a possible solution.

It is a gui application tested on windows that needs to contact an api using the websocket client. — Bruhman, Apr 09 '21 at 05:10
How did you build the jar? Are the dependencies (libraries) on the classpath when you run the program? — Jim Garrison, Apr 09 '21 at 05:11

score 0 · Answer 1 · answered Apr 09 '21 at 05:17

If you are saying that you run maven install and gets a "normal" jar file, maybe you are missing the plugin to add the dependencies to your jar. So after you run a simple mvn clean package, and run the jar file. I believe that could work.

  <plugin>
    <artifactId>maven-assembly-plugin</artifactId>
    <executions>
      <execution>
        <phase>package</phase>
        <goals>
          <goal>single</goal>
        </goals>
      </execution>
    </executions>
    <configuration>
      <descriptorRefs>
        <descriptorRef>jar-with-dependencies</descriptorRef>
      </descriptorRefs>
    </configuration>
  </plugin>

Java Maven project cannot find dependency

1 Answers1