Develop Reference

Getting "java.lang.NoClassDefFoundError: org/apache/kafka/clients/consumer/KafkaConsumer" when I try to run the Java -jar command after maven build [duplicate]

Is there a way to force maven(2.0.9) to include all the dependencies in a single jar file?
I have a project the builds into a single jar file. I want the classes from dependencies to be copied into the jar as well.
Update: I know that I cant just include a jar file in a jar file. I'm searching for a way to unpack the jars that are specified as dependencies, and package the class files into my jar.

You can do this using the maven-assembly plugin with the "jar-with-dependencies" descriptor. Here's the relevant chunk from one of our pom.xml's that does this:
<build>
<plugins>
<!-- any other plugins -->
<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>
</plugins>
</build>

With Maven 2, the right way to do this is to use the Maven2 Assembly Plugin which has a pre-defined descriptor file for this purpose and that you could just use on the command line:
mvn assembly:assembly -DdescriptorId=jar-with-dependencies
If you want to make this jar executable, just add the main class to be run to the plugin configuration:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<configuration>
<archive>
<manifest>
<mainClass>my.package.to.my.MainClass</mainClass>
</manifest>
</archive>
</configuration>
</plugin>
If you want to create that assembly as part of the normal build process, you should bind the single or directory-single goal (the assembly goal should ONLY be run from the command line) to a lifecycle phase (package makes sense), something like this:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<executions>
<execution>
<id>create-my-bundle</id>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
<configuration>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
...
</configuration>
</execution>
</executions>
</plugin>
Adapt the configuration element to suit your needs (for example with the manifest stuff as spoken).

If you want to do an executable jar file, them need set the main class too. So the full configuration should be.
<plugins>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
</execution>
</executions>
<configuration>
<!-- ... -->
<archive>
<manifest>
<mainClass>fully.qualified.MainClass</mainClass>
</manifest>
</archive>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
</plugin>
</plugins>

Method 1: Copy the dependencies' JAR files into target/lib and then add them to the JAR's classpath in MANIFEST:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<configuration>
<outputDirectory>${project.build.directory}/lib</outputDirectory>
<excludeTransitive>false</excludeTransitive>
<stripVersion>false</stripVersion>
</configuration>
<executions>
<execution>
<id>copy-dependencies</id>
<phase>package</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
</execution>
</executions>
</plugin>
<!-- Add LIB folder to classPath -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.4</version>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<classpathPrefix>lib/</classpathPrefix>
</manifest>
</archive>
</configuration>
</plugin>
Method 2: Unpack all dependencies and repack their classes and resources into one flat JAR. Note: The overlapping resources will be randomly lost!
<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>

There's the shade maven plugin. It can be used to package and rename dependencies (to omit dependency problems on the classpath).

You can use the newly created jar using a <classifier> tag.
<dependencies>
<dependency>
<groupId>your.group.id</groupId>
<artifactId>your.artifact.id</artifactId>
<version>1.0</version>
<type>jar</type>
<classifier>jar-with-dependencies</classifier>
</dependency>
</dependencies>

If you (like me) dont particularly like the jar-with-dependencies approach described above,
the maven-solution I prefer is to simply build a WAR-project,
even if it is only a stand-alone java application you are building:
Make a normal maven jar-project, that will build your jar-file (without the dependencies).
Also, setup a maven war-project (with only an empty src/main/webapp/WEB-INF/web.xml file, which will avoid a warning/error in the maven-build), that only has your jar-project as a dependency, and make your jar-project a <module> under your war-project. (This war-project is only a simple trick to wrap all your jar-file dependencies into a zip-file.)
Build the war-project to produce the war-file.
In the deployment-step, simply rename your .war-file to *.zip and unzip it.
You should now have a lib-directory (which you can move where you want it) with your jar and all the dependencies you need to run your application:
java -cp 'path/lib/*' MainClass
(The wildcard in classpath works in Java-6 or higher)
I think this is both simpler to setup in maven (no need to mess around with the assembly plugin) and also gives you a clearer view of the application-structure (you will see the version-numbers of all dependent jars in plain view, and avoid clogging everything into a single jar-file).

http://fiji.sc/Uber-JAR provides an excellent explanation of the alternatives:
There are three common methods for constructing an uber-JAR:
Unshaded. Unpack all JAR files, then repack them into a single JAR.
Pro: Works with Java's default class loader.
Con: Files present in multiple JAR files with the same path (e.g.,
META-INF/services/javax.script.ScriptEngineFactory) will overwrite one
another, resulting in faulty behavior.
Tools: Maven Assembly
Plugin, Classworlds Uberjar
Shaded. Same as unshaded, but rename (i.e., "shade") all packages of all dependencies.
Pro: Works with Java's default class loader.
Avoids some (not all) dependency version clashes.
Con: Files
present in multiple JAR files with the same path (e.g.,
META-INF/services/javax.script.ScriptEngineFactory) will overwrite one
another, resulting in faulty behavior.
Tools: Maven Shade Plugin
JAR of JARs. The final JAR file contains the other JAR files embedded within.
Pro: Avoids dependency version clashes. All
resource files are preserved.
Con: Needs to bundle a special
"bootstrap" classloader to enable Java to load classes from the
wrapped JAR files. Debugging class loader issues becomes more complex.
Tools: Eclipse JAR File Exporter, One-JAR.

My definitive solution on Eclipse Luna and m2eclipse:
Custom Classloader (download and add to your project, 5 classes only)
:http://git.eclipse.org/c/jdt/eclipse.jdt.ui.git/plain/org.eclipse.jdt.ui/jar%20in%20jar%20loader/org/eclipse/jdt/internal/jarinjarloader/;
this classloader is very best of one-jar classloader and very fast;
<project.mainClass>org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader</project.mainClass>
<project.realMainClass>my.Class</project.realMainClass>
Edit in JIJConstants "Rsrc-Class-Path" to "Class-Path"
mvn clean dependency:copy-dependencies package
is created a jar with dependencies in lib folder with a thin classloader
<build>
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.java</include>
<include>**/*.properties</include>
</includes>
</resource>
<resource>
<directory>src/main/resources</directory>
<filtering>true</filtering>
<includes>
<include>**/*</include>
</includes>
<targetPath>META-INF/</targetPath>
</resource>
<resource>
<directory>${project.build.directory}/dependency/</directory>
<includes>
<include>*.jar</include>
</includes>
<targetPath>lib/</targetPath>
</resource>
</resources>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<mainClass>${project.mainClass}</mainClass>
<classpathPrefix>lib/</classpathPrefix>
</manifest>
<manifestEntries>
<Rsrc-Main-Class>${project.realMainClass} </Rsrc-Main-Class>
<Class-Path>./</Class-Path>
</manifestEntries>
</archive>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<id>copy-dependencies</id>
<phase>package</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</pluginManagement>
</build>

Putting Maven aside, you can put JAR libraries inside the Main Jar but you will need to use your own classloader.
Check this project: One-JAR link text

I was trying to do sth similar, but I didn't want all jars to be included. I wanted to include some specific directories from the given dependency. In addition classifier tag was already occupied, so I couldn't do:
<dependencies>
<dependency>
<groupId>your.group.id</groupId>
<artifactId>your.artifact.id</artifactId>
<version>1.0</version>
<type>jar</type>
<classifier>jar-with-dependencies</classifier>
</dependency>
</dependencies>
I used maven-dependency-plugin and unpack goal
And unpacked what I wanted to the ${project.build.directory}/classes, otherwise it will be omitted
Because it was in the classes directory, maven finally placed it in the jar
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<id>unpack</id>
<phase>prepare-package</phase>
<goals>
<goal>unpack</goal>
</goals>
<configuration>
<artifactItems>
<artifactItem>
<groupId>my.group</groupId>
<artifactId>my.artifact</artifactId>
<classifier>occupied</classifier>
<version>1.0</version>
<type>jar</type>
</artifactItem>
</artifactItems>
<outputDirectory>${project.build.directory}/classes</outputDirectory>
<includes>aaa/**, bbb/**, ccc/**</includes>
</configuration>
</execution>
</executions>
</plugin>

This post may be a bit old, but I also had the same problem recently. The first solution proposed by John Stauffer is a good one, but I had some problems as I am working this spring. The spring's dependency-jars I use have some property files and xml-schemas declaration which share the same paths and names. Although these jars come from the same versions, the jar-with-dependencies maven-goal was overwriting theses file with the last file found.
In the end, the application was not able to start as the spring jars could not find the correct properties files. In this case the solution propose by Rop have solved my problem.
Also since then, the spring-boot project now exist. It has a very cool way to manage this problem by providing a maven goal which overload the package goal and provide its own class loader. See spring-boots Reference Guide

Have a look at this answer:
I am creating an installer that runs as a Java JAR file and it needs to unpack WAR and JAR files into appropriate places in the installation directory. The dependency plugin can be used in the package phase with the copy goal and it will download any file in the Maven repository (including WAR files) and write them where ever you need them. I changed the output directory to ${project.build.directory}/classes and then end result is that the normal JAR task includes my files just fine. I can then extract them and write them into the installation directory.
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<id>getWar</id>
<phase>package</phase>
<goals>
<goal>copy</goal>
</goals>
<configuration>
<artifactItems>
<artifactItem>
<groupId>the.group.I.use</groupId>
<artifactId>MyServerServer</artifactId>
<version>${env.JAVA_SERVER_REL_VER}</version>
<type>war</type>
<destFileName>myWar.war</destFileName>
</artifactItem>
</artifactItems>
<outputDirectory>${project.build.directory}/classes</outputDirectory>
</configuration>
</execution>
</executions>

Thanks
I have added below snippet in POM.xml file and Mp problem resolved and
create fat jar file that include all dependent jars.
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
</execution>
</executions>
<configuration>
<descriptorRefs>
<descriptorRef>dependencies</descriptorRef>
</descriptorRefs>
</configuration>
</plugin>
</plugins>

I found this to be the clearest answer; other answers here were missing things that weren't obvious to me such as mvn clean package command for example, and adding the plugin separately as a dependancy also. All of which are probably obvious to more habitual maven users.
https://howtodoinjava.com/maven/executable-jar-with-dependencies/

To make it more simple, You can use the below plugin.
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
<configuration>
<classifier>spring-boot</classifier>
<mainClass>
com.nirav.certificate.CertificateUtility
</mainClass>
</configuration>
</execution>
</executions>
</plugin>

how to avoid resource override when using maven to generate runnable jar?

I have one maven project and depend one jar which contain one resource file(c3p0.xml), I copy the resource into my src/main/resource folder and change the content according to my requirements so that I can use it.
but after I run the mvn assembly:assembly command, the generated jar contained resource's content is old in dependence jar not my content in src/main/resource How to handle it?
My pom.xml's key content is as followed:
<plugin>
<!-- mvn assembly:assembly -->
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<version>2.4</version>
<configuration>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
<archive>
<manifest>
<mainClass>com.fastcheck.RequestUrl</mainClass>
</manifest>
</archive>
</configuration>
</plugin>

The jar-with-dependencies assembly mechanism uses the maven dependencies you've declared, and not from what's in your resources directory. If you want to use a newer version of a jar, declare a newer version as the dependency in your .pom file.

You should bind maven-assembly-plugin to the build life cycle like this:
<project>
[...]
<build>
[...]
<plugins>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<version>2.4</version>
<configuration>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
<executions>
<execution>
<id>make-assembly</id> <!-- this is used for inheritance merges -->
<phase>package</phase> <!-- bind to the packaging phase -->
<goals>
<goal>single</goal>
</goals>
</execution>
</executions>
</plugin>
[...]
</project>
which will be execute the maven-assembly-plugin within the package life cylce phase.

Exporting multiple projects as jars

How do I export multiple projects as individual jar files each, so as to have a 1:1 ratio of project to jar? I have thousands of projects, and exporting each of them one by one would take way too long, and exporting them all as one jar is also not ideal, because I run them individually via the cron scheduler.
Edit - What I need, to be specific, is exactly what I get from running "Export -> Runnable JAR" in Eclipse, having "Package required libraries into generated JAR", except to do it in a faster way. Maven is apparently good for this, but I'm having trouble getting it to work like I want.

You can use Maven. Then you just have to run a command like mvn package in each project folders to generate the jar files. You can write a script to automate this process.

To get the maven to create a runable jar with all your dependencies try doing this:
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.4</version>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<mainClass>com.whatever.YourMainClass</mainClass>
</manifest>
</archive>
</configuration>
</plugin>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<version>2.2.1</version>
<configuration>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
<archive>
<manifest>
<mainClass>com.whatever.YourMainClass</mainClass>
</manifest>
</archive>
</configuration>
<executions>
<execution>
<id>make-assembly</id> <!-- this is used for inheritance merges -->
<phase>package</phase> <!-- bind to the packaging phase -->
<goals>
<goal>single</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>

Problems running executable jar with dependencies

Hey so I have been working on a project that I want to be able to run as an executable jar from the command line. I have been able to create the jar with dependencies using Mavens assembly:single command. My pom looks like this.
<build>
<plugins>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<version>2.3</version>
<configuration>
<archive>
<manifest>
<mainClass>org.openmetadata.main.OmadUpdate</mainClass>
</manifest>
</archive>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
</plugin>
</plugins>
</build>
The build is successful and creates the jar omad-update-0.0.1-SNAPSHOT-jar-with-dependencies.jar. I go to my projects target folder in the command line and type
java -jar omad-update-0.0.1-SNAPSHOT-jar-with-dependencies.jar
I have also tried
java -cp omad-update-0.0.1-SNAPSHOT-jar-with-dependencies.jar org.openmetadata.main.OmadUpdate
Unfortunately in each case I am given a java.lang.NoClassDefFoundError: org/openmetadata/main/OmadUpdate. I am confused because I know my main class is in the package org.openmetadata.main and yet it is not found. I find this especially confusing because in my pom I specify that class as my main class. I have tried changing the name of the main class to src.main.java.org.openmetadata.main.OmadUpdate and simply OmadUpdate as well but neither seems to have an effect. Thanks for any help in advance.

I do not see a Class-Path entry in the manifest above, but your very long filename mentions dependencies. If there are jars within this jar file that your program is dependent on, you must enumerate them in the Class-Path section. See Adding Classes to the JAR File's Classpath for more details.

Another option might be to use the onejar-maven-plugin. Unfortunately the usage page is a bit scarce, but the plugin does what is supposed to when configured correctly.

I finally have been able to get this to work by adding the following code to my pom.
<build>
<plugins>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<version>2.3</version>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<mainClass>org.openmetadata.omadupdate.OmadUpdate</mainClass>
</manifest>
</archive>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
<executions>
<execution>
<id>make-assembly</id> <!-- this is used for inheritance merges -->
<phase>package</phase> <!-- bind to the packaging phase -->
<goals>
<goal>single</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
Without the executions tag in the pom along with its children only the maven dependencies will be added to the jar and the classes from the project itself will not be added.

Including dependencies in a jar with Maven

Is there a way to force maven(2.0.9) to include all the dependencies in a single jar file?
I have a project the builds into a single jar file. I want the classes from dependencies to be copied into the jar as well.
Update: I know that I cant just include a jar file in a jar file. I'm searching for a way to unpack the jars that are specified as dependencies, and package the class files into my jar.

You can do this using the maven-assembly plugin with the "jar-with-dependencies" descriptor. Here's the relevant chunk from one of our pom.xml's that does this:
<build>
<plugins>
<!-- any other plugins -->
<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>
</plugins>
</build>

With Maven 2, the right way to do this is to use the Maven2 Assembly Plugin which has a pre-defined descriptor file for this purpose and that you could just use on the command line:
mvn assembly:assembly -DdescriptorId=jar-with-dependencies
If you want to make this jar executable, just add the main class to be run to the plugin configuration:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<configuration>
<archive>
<manifest>
<mainClass>my.package.to.my.MainClass</mainClass>
</manifest>
</archive>
</configuration>
</plugin>
If you want to create that assembly as part of the normal build process, you should bind the single or directory-single goal (the assembly goal should ONLY be run from the command line) to a lifecycle phase (package makes sense), something like this:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<executions>
<execution>
<id>create-my-bundle</id>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
<configuration>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
...
</configuration>
</execution>
</executions>
</plugin>
Adapt the configuration element to suit your needs (for example with the manifest stuff as spoken).

If you want to do an executable jar file, them need set the main class too. So the full configuration should be.
<plugins>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
</execution>
</executions>
<configuration>
<!-- ... -->
<archive>
<manifest>
<mainClass>fully.qualified.MainClass</mainClass>
</manifest>
</archive>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
</plugin>
</plugins>

Method 1: Copy the dependencies' JAR files into target/lib and then add them to the JAR's classpath in MANIFEST:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<configuration>
<outputDirectory>${project.build.directory}/lib</outputDirectory>
<excludeTransitive>false</excludeTransitive>
<stripVersion>false</stripVersion>
</configuration>
<executions>
<execution>
<id>copy-dependencies</id>
<phase>package</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
</execution>
</executions>
</plugin>
<!-- Add LIB folder to classPath -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.4</version>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<classpathPrefix>lib/</classpathPrefix>
</manifest>
</archive>
</configuration>
</plugin>
Method 2: Unpack all dependencies and repack their classes and resources into one flat JAR. Note: The overlapping resources will be randomly lost!
<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>

There's the shade maven plugin. It can be used to package and rename dependencies (to omit dependency problems on the classpath).

You can use the newly created jar using a <classifier> tag.
<dependencies>
<dependency>
<groupId>your.group.id</groupId>
<artifactId>your.artifact.id</artifactId>
<version>1.0</version>
<type>jar</type>
<classifier>jar-with-dependencies</classifier>
</dependency>
</dependencies>

If you (like me) dont particularly like the jar-with-dependencies approach described above,
the maven-solution I prefer is to simply build a WAR-project,
even if it is only a stand-alone java application you are building:
Make a normal maven jar-project, that will build your jar-file (without the dependencies).
Also, setup a maven war-project (with only an empty src/main/webapp/WEB-INF/web.xml file, which will avoid a warning/error in the maven-build), that only has your jar-project as a dependency, and make your jar-project a <module> under your war-project. (This war-project is only a simple trick to wrap all your jar-file dependencies into a zip-file.)
Build the war-project to produce the war-file.
In the deployment-step, simply rename your .war-file to *.zip and unzip it.
You should now have a lib-directory (which you can move where you want it) with your jar and all the dependencies you need to run your application:
java -cp 'path/lib/*' MainClass
(The wildcard in classpath works in Java-6 or higher)
I think this is both simpler to setup in maven (no need to mess around with the assembly plugin) and also gives you a clearer view of the application-structure (you will see the version-numbers of all dependent jars in plain view, and avoid clogging everything into a single jar-file).

http://fiji.sc/Uber-JAR provides an excellent explanation of the alternatives:
There are three common methods for constructing an uber-JAR:
Unshaded. Unpack all JAR files, then repack them into a single JAR.
Pro: Works with Java's default class loader.
Con: Files present in multiple JAR files with the same path (e.g.,
META-INF/services/javax.script.ScriptEngineFactory) will overwrite one
another, resulting in faulty behavior.
Tools: Maven Assembly
Plugin, Classworlds Uberjar
Shaded. Same as unshaded, but rename (i.e., "shade") all packages of all dependencies.
Pro: Works with Java's default class loader.
Avoids some (not all) dependency version clashes.
Con: Files
present in multiple JAR files with the same path (e.g.,
META-INF/services/javax.script.ScriptEngineFactory) will overwrite one
another, resulting in faulty behavior.
Tools: Maven Shade Plugin
JAR of JARs. The final JAR file contains the other JAR files embedded within.
Pro: Avoids dependency version clashes. All
resource files are preserved.
Con: Needs to bundle a special
"bootstrap" classloader to enable Java to load classes from the
wrapped JAR files. Debugging class loader issues becomes more complex.
Tools: Eclipse JAR File Exporter, One-JAR.

My definitive solution on Eclipse Luna and m2eclipse:
Custom Classloader (download and add to your project, 5 classes only)
:http://git.eclipse.org/c/jdt/eclipse.jdt.ui.git/plain/org.eclipse.jdt.ui/jar%20in%20jar%20loader/org/eclipse/jdt/internal/jarinjarloader/;
this classloader is very best of one-jar classloader and very fast;
<project.mainClass>org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader</project.mainClass>
<project.realMainClass>my.Class</project.realMainClass>
Edit in JIJConstants "Rsrc-Class-Path" to "Class-Path"
mvn clean dependency:copy-dependencies package
is created a jar with dependencies in lib folder with a thin classloader
<build>
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.java</include>
<include>**/*.properties</include>
</includes>
</resource>
<resource>
<directory>src/main/resources</directory>
<filtering>true</filtering>
<includes>
<include>**/*</include>
</includes>
<targetPath>META-INF/</targetPath>
</resource>
<resource>
<directory>${project.build.directory}/dependency/</directory>
<includes>
<include>*.jar</include>
</includes>
<targetPath>lib/</targetPath>
</resource>
</resources>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<mainClass>${project.mainClass}</mainClass>
<classpathPrefix>lib/</classpathPrefix>
</manifest>
<manifestEntries>
<Rsrc-Main-Class>${project.realMainClass} </Rsrc-Main-Class>
<Class-Path>./</Class-Path>
</manifestEntries>
</archive>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<id>copy-dependencies</id>
<phase>package</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</pluginManagement>
</build>

Putting Maven aside, you can put JAR libraries inside the Main Jar but you will need to use your own classloader.
Check this project: One-JAR link text

I was trying to do sth similar, but I didn't want all jars to be included. I wanted to include some specific directories from the given dependency. In addition classifier tag was already occupied, so I couldn't do:
<dependencies>
<dependency>
<groupId>your.group.id</groupId>
<artifactId>your.artifact.id</artifactId>
<version>1.0</version>
<type>jar</type>
<classifier>jar-with-dependencies</classifier>
</dependency>
</dependencies>
I used maven-dependency-plugin and unpack goal
And unpacked what I wanted to the ${project.build.directory}/classes, otherwise it will be omitted
Because it was in the classes directory, maven finally placed it in the jar
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<id>unpack</id>
<phase>prepare-package</phase>
<goals>
<goal>unpack</goal>
</goals>
<configuration>
<artifactItems>
<artifactItem>
<groupId>my.group</groupId>
<artifactId>my.artifact</artifactId>
<classifier>occupied</classifier>
<version>1.0</version>
<type>jar</type>
</artifactItem>
</artifactItems>
<outputDirectory>${project.build.directory}/classes</outputDirectory>
<includes>aaa/**, bbb/**, ccc/**</includes>
</configuration>
</execution>
</executions>
</plugin>

This post may be a bit old, but I also had the same problem recently. The first solution proposed by John Stauffer is a good one, but I had some problems as I am working this spring. The spring's dependency-jars I use have some property files and xml-schemas declaration which share the same paths and names. Although these jars come from the same versions, the jar-with-dependencies maven-goal was overwriting theses file with the last file found.
In the end, the application was not able to start as the spring jars could not find the correct properties files. In this case the solution propose by Rop have solved my problem.
Also since then, the spring-boot project now exist. It has a very cool way to manage this problem by providing a maven goal which overload the package goal and provide its own class loader. See spring-boots Reference Guide

Have a look at this answer:
I am creating an installer that runs as a Java JAR file and it needs to unpack WAR and JAR files into appropriate places in the installation directory. The dependency plugin can be used in the package phase with the copy goal and it will download any file in the Maven repository (including WAR files) and write them where ever you need them. I changed the output directory to ${project.build.directory}/classes and then end result is that the normal JAR task includes my files just fine. I can then extract them and write them into the installation directory.
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<id>getWar</id>
<phase>package</phase>
<goals>
<goal>copy</goal>
</goals>
<configuration>
<artifactItems>
<artifactItem>
<groupId>the.group.I.use</groupId>
<artifactId>MyServerServer</artifactId>
<version>${env.JAVA_SERVER_REL_VER}</version>
<type>war</type>
<destFileName>myWar.war</destFileName>
</artifactItem>
</artifactItems>
<outputDirectory>${project.build.directory}/classes</outputDirectory>
</configuration>
</execution>
</executions>

Thanks
I have added below snippet in POM.xml file and Mp problem resolved and
create fat jar file that include all dependent jars.
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
</execution>
</executions>
<configuration>
<descriptorRefs>
<descriptorRef>dependencies</descriptorRef>
</descriptorRefs>
</configuration>
</plugin>
</plugins>

I found this to be the clearest answer; other answers here were missing things that weren't obvious to me such as mvn clean package command for example, and adding the plugin separately as a dependancy also. All of which are probably obvious to more habitual maven users.
https://howtodoinjava.com/maven/executable-jar-with-dependencies/

To make it more simple, You can use the below plugin.
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
<configuration>
<classifier>spring-boot</classifier>
<mainClass>
com.nirav.certificate.CertificateUtility
</mainClass>
</configuration>
</execution>
</executions>
</plugin>