CODEWITHSUNDEEP
javamavenlog4j
Biscuit128
Biscuit128

Reputation: 5398

Cannot find log4j on the class path - Maven

I am trying to run my application from the command line - I do the following - build the application using mvn clean verify which produces a jar to which i run the jar in the normal way java -jar name.jar

I have log4j configured in my pom.xml as follows;

<dependency>
    <groupId>log4j</groupId>
    <artifactId>log4j</artifactId>
    <version>1.2.17</version>
</dependency>

And I have setup the application to create a manifest as seen below;

<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.4</version>
<configuration>
    <archive>
        <manifest>
            <addClasspath>true</addClasspath>
            <mainClass>com.me.main.Main</mainClass>
        </manifest>
    </archive>
</configuration>

However, when I run the jar I keep getting the following exception - 

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/log4j/Logger
    at com.me.main.Main.<clinit>(Main.java:23)
Caused by: java.lang.ClassNotFoundException: org.apache.log4j.Logger
    at java.net.URLClassLoader$1.run(URLClassLoader.java:372)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:360)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 1 more

Why does maven not download the dependancy and put it in to the relevant location? What am i missing potentially from my project setup?

Thanks

Upvotes: 0

Views: 1783

Answers (1)

lexicore
lexicore

Reputation: 43661

Maven just builds your JAR and manages dependencies in the build time. It's a build tool after all. if is your job to take care of dependencies in the runtime.

I think you have two options for this.

One is the Class-Path setting in the manifest. I have never used it but I thing you'll have to do something like:

Class-Path: log4j-1.2.7.jar

An the java -jar your.jar should work as long as log4j-1.2.7.jar is placed next to it. As I said, I have never tried this, have no idea if the syntax is right, don't trust me here.

If you want to go this way, you might think about preparing a zip assembly, otherwise people will get crazy trying to figure out how to call your application.

Another options would be to use the maven-shade-plugin. Would be something like:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-shade-plugin</artifactId>
    <executions>
        <execution>
            <phase>package</phase>
            <goals>
                <goal>shade</goal>
            </goals>
            <configuration>
                <transformers>
                    <transformer 
                        implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                        <mainClass>com.me.main.Main</mainClass>
                    </transformer>
                </transformers>
            </configuration>
        </execution>
    </executions>
</plugin>

You'll get a big JAR with everything inside.

I personally think it is a way better option. But be very careful with licenses. IANAL but check redistribution clauses.

Upvotes: 2

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