[FIXED] Integrating slf4j with maven

Issue

Hello guys I am new to Maven and I am trying to integrate slf4j in a maven project Here is my pom.xml file

<dependency>
 <groupId>org.slf4j</groupId>
 <artifactId>slf4j-api</artifactId>
 <version>1.7.9</version>
</dependency>

And I have these two lines in my main function

Logger logger = LoggerFactory.getLogger(App.class);
logger.info("Hello World");

Project is compiled and packaged successfully but when I try to run it through
java -cp target/maven-1.0-SNAPSHOT.jar com.goutam.maven.App The following Exception is thrown

Exception in thread "main" java.lang.NoClassDefFoundError: org/slf4j/LoggerFactory
    at com.goutam.maven.App.main(App.java:11)
Caused by: java.lang.ClassNotFoundException: org.slf4j.LoggerFactory
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:358)

Solution

I don't like the idea of building fat jars, as we loose some flexibilities in this approach.

Rather would advocate for copy-dependencies plugin in maven.

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-dependency-plugin</artifactId>
    <version>2.9</version>
    <executions>
      <execution>
        <id>copy-dependencies</id>
        <phase>install</phase>
        <goals>
          <goal>copy-dependencies</goal>
        </goals>
        <configuration>
          <outputDirectory>${project.build.directory}/lib</outputDirectory>
          <overWriteReleases>false</overWriteReleases>
          <overWriteSnapshots>false</overWriteSnapshots>
          <overWriteIfNewer>true</overWriteIfNewer>
        </configuration>
      </execution>
    </executions>
  </plugin>

Coupling it along with maven-jar-plugin. Read this for details.

Assuming the third party dependencies are copied into target/lib folder.

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-jar-plugin</artifactId>
    <version>2.5</version>
    <configuration>
        <archive>
            <manifest>
                <mainClass>main class</mainClass>
                <addClasspath>true</addClasspath>
                <classpathPrefix>lib/</classpathPrefix>
            </manifest>
        </archive>
    </configuration>
</plugin>

Answered By - Himanshu Bhardwaj
Answer Checked By - Dawn Plyler (JavaFixing Volunteer)