Maven exec works, but java -jar does not

Question

I have simple maven project with only one dependency. I can install it and run it command-line via Exec Maven Plugin:

mvn exec:java -D"exec.mainClass"="com.MyClass"

After packaging maven generates a .jar file in my directory. With a help of Maven JAR Plugin I made its manifest to know my main method class. It looks like:

...
Created-By: Apache Maven 3.3.1
Build-Jdk: 1.8.0_66
Main-Class: com.MyClass

Now I want to run this .jar file like regular java executable using java command, but after doing the following:

java -jar myFile.jar

it gives an error java.lang.NoClassDefFoundError concerning my only dependency.

How can I make maven to add all dependencies into my executable jar file?

Something like the Maven Assembly plugin to create a fat jar? https://maven.apache.org/plugins/maven-assembly-plugin/ and https://www.mkyong.com/maven/create-a-fat-jar-file-maven-assembly-plugin/ — , Jul 17 '18 at 13:35

score 2 · Answer 1 · answered Jul 17 '18 at 15:26

One way to achieve this is using Apache Maven Shade Plugin:

This plugin provides the capability to package the artifact in an uber-jar, including its dependencies and to shade - i.e. rename - the packages of some of the dependencies.

This plugin has some advantages for large project with many dependencies. This is explained here: Difference between maven plugins ( assembly-plugins , jar-plugins , shaded-plugins)

In my project I use it with this configuration:

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-shade-plugin</artifactId>
  <version>2.4.2</version>
  <executions>
    <execution>
      <phase>package</phase>
      <goals>
        <goal>shade</goal>
      </goals>
      <configuration>
        <filters>
          <filter>
            <artifact>*:*</artifact>
            <excludes>
              <exclude>META-INF/*.SF</exclude>
              <exclude>META-INF/*.DSA</exclude>
              <exclude>META-INF/*.RSA</exclude>
            </excludes>
          </filter>
        </filters>
        <transformers>
          <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
            <mainClass>com.xxx.tools.imagedump.ImageDumpLauncher</mainClass>
          </transformer>
          <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
            <resource>META-INF/spring.handlers</resource>
          </transformer>
          <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
            <resource>META-INF/spring.schemas</resource>
          </transformer>
        </transformers>
      </configuration>
    </execution>
  </executions>
</plugin>

This one is right answer also, but as my case is simple one, then @Alessandro's variant is more acceptable. I give you thumb up ;) — Serob_b, Jul 17 '18 at 19:13

score 1 · Accepted Answer · answered Jul 17 '18 at 13:37

You could use the Apache Maven Assembly Plugin, in order to create a jar with all its dependencies, so your pom.xml should be like the following:

<plugin>
    <artifactId>maven-assembly-plugin</artifactId>
    <executions>
        <execution>
            <phase>package</phase>
            <goals>
                <goal>single</goal>
            </goals>
        </execution>
    </executions>
    <configuration>
        <archive>
            <manifest>
                <addClasspath>true</addClasspath>
                <classpathPrefix>lib/</classpathPrefix>
                <mainClass>mypackage.myclass</mainClass>
            </manifest>
        </archive>
        <descriptorRefs>
            <descriptorRef>jar-with-dependencies</descriptorRef>
        </descriptorRefs>
    </configuration>
</plugin>

I hope it helps you, bye.

It worked! I didn't even use 'addClasspath' and 'classpathPrefix' — Serob_b, Jul 17 '18 at 19:09

Maven exec works, but java -jar does not

2 Answers2