How do I put all required JAR files in a library folder inside the final JAR file with Maven?

Question

I am using Maven in my standalone application, and I want to package all the dependencies in my JAR file inside a library folder, as mentioned in one of the answers here:

How can I create an executable JAR with dependencies using Maven?

I want my final JAR file to have a library folder that contains the dependencies as JAR files, not like what the maven-shade-plugin that puts the dependencies in the form of folders like the Maven hierarchy in the .m2 folder.

Well, actually the current configuration does what I want, but I am having a problem with loading the JAR files when running the application. I can't load the classes.

Here's my configuration:

<plugins>

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

    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-jar-plugin</artifactId>
        <configuration>
            <archive>
                <manifest>
                    <addClasspath>true</addClasspath>
                    <classpathPrefix>lib/</classpathPrefix>
                    <mainClass>com.myapp.MainClass</mainClass>
                </manifest>
            </archive>
        </configuration>
    </plugin>

    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <configuration>
            <source>1.6</source>
            <target>1.6</target>
        </configuration>
    </plugin>

    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-dependency-plugin</artifactId>
        <executions>
            <execution>
                <id>install</id>
                <phase>install</phase>
                <goals>
                    <goal>sources</goal>
                </goals>
            </execution>
        </executions>
    </plugin>

    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-resources-plugin</artifactId>
        <version>2.5</version>
        <configuration>
            <encoding>UTF-8</encoding>
        </configuration>
    </plugin>

</plugins>

The project runs fine from Eclipse, and the JAR files are put in the library folder inside my final JAR file as I want, but when running the final JAR file from the target folder I always get ClassNotFoundException:

Exception in thread "main" java.lang.NoClassDefFoundError: org/springframework/context/ApplicationContext
Caused by: java.lang.ClassNotFoundException: org.springframework.context.ApplicationContext
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
Could not find the main class: com.myapp.MainClass. Program will exit.

How can I fix this exception?

which command do you use to run the jar? probably you may prefer maven exec plugin? — Andrey Borisov, Aug 01 '12 at 12:05
Is the exception message out of date compared with the POM file? It seems the main class `com.myapp.MainClass` is being searched for, not `com.tastycafe.MainClass`. — Duncan Jones, Aug 01 '12 at 12:06
Note that if you want jars inside the jar, then the standard classloaders in Java cannot understand them. — Thorbjørn Ravn Andersen, May 08 '15 at 14:17
How to make it place the maven dependencies in a lib folder but outside the JAR? — ed22, Jul 02 '18 at 13:32

score 91 · Answer 1 · edited Mar 14 '17 at 21:49

The following is my solution. Test it if it works for you:

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

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-jar-plugin</artifactId>
    <configuration>
        <archive>
            <manifest>
                <addClasspath>true</addClasspath>
                <!-- <classpathPrefix>lib</classpathPrefix> -->
                <!-- <mainClass>test.org.Cliente</mainClass> -->
            </manifest>
            <manifestEntries>
                <Class-Path>lib/</Class-Path>
            </manifestEntries>
        </archive>
    </configuration>
</plugin>

The first plugin puts all dependencies in the target/classes/lib folder, and the second one includes the library folder in the final JAR file, and configures the Manifest.mf file.

But then you will need to add custom classloading code to load the JAR files.

Or, to avoid custom classloading, you can use "${project.build.directory}/lib, but in this case, you don't have dependencies inside the final JAR file, which defeats the purpose.

It's been two years since the question was asked. The problem of nested JAR files persists nevertheless. I hope it helps somebody.

what do I miss? This creates a manifest classpath entry containing "lib/" and all single jar from the lib folder. Is this intended? Why? — gapvision, Feb 25 '16 at 17:50
It worked after I changed "${project.build.directory}/classes/lib" to ${project.build.directory}/lib — Rajendra Thorat, Sep 30 '16 at 13:22

score 35 · Answer 2 · edited Mar 15 '16 at 12:35

35

Updated:

<build> 
  <plugins> 
    <plugin> 
    <artifactId>maven-dependency-plugin</artifactId> 
    <executions> 
      <execution> 
        <phase>install</phase> 
          <goals> 
            <goal>copy-dependencies</goal> 
          </goals> 
          <configuration> 
             <outputDirectory>${project.build.directory}/lib</outputDirectory> 
          </configuration> 
        </execution> 
      </executions> 
    </plugin> 
  </plugins> 
</build>

edited Mar 15 '16 at 12:35

dan

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answered Aug 01 '12 at 13:02

Ahmet Karakaya

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4

this puts the lib folder outside the jar (which is not what i want). is that better than putting the lib inside the jar ? and how to deliver the application to the client in this case ? – Mahmoud Saleh Aug 01 '12 at 13:30
it is more clear for me now. let me make a google search. But I would like to know why you want to copy all dependency jar file in specified folder inside the executable jar file. If all dependency jar files are inside the jar file, why do you need to locate them in a lib folder? – Ahmet Karakaya Aug 01 '12 at 13:35
Where I should put the lib folder so that all external dependencies are loaded at runtime? – CoreThought Sep 16 '22 at 06:23

score 24 · Answer 3 · edited Dec 21 '20 at 15:01

24

The simplest and the most efficient way is to use an uber plugin like this:

          <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-shade-plugin</artifactId>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>shade</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <finalName>uber-${project.artifactId}-${project.version}</finalName>
            </configuration>
        </plugin>

You will have de-normalized all in one JAR file.

edited Dec 21 '20 at 15:01

Adam Michalak

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answered Aug 01 '12 at 11:57

Andrey Borisov

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use it in addition to my current config ? and what this plugin does exactly ? – Mahmoud Saleh Aug 01 '12 at 11:59
18

i don't want my jar file to look like this, i want to have all the dependencies in a lib folder inside the jar file as netbean does. – Mahmoud Saleh Aug 01 '12 at 12:02
This works for me, but it produces a giant jar file. The ant file I am trying to port generates a 495K jar, this produces an 18M file. – bb121622 Oct 04 '20 at 00:53

Cybran · Answer 4 · 2017-06-04T11:11:55.613

14

The executable packer maven plugin can be used for exactly that purpose: creating standalone java applications containing all dependencies as JAR files in a specific folder.

Just add the following to your pom.xml inside the <build><plugins> section (be sure to replace the value of mainClass accordingly):

<plugin>
    <groupId>de.ntcomputer</groupId>
    <artifactId>executable-packer-maven-plugin</artifactId>
    <version>1.0.1</version>
    <configuration>
        <mainClass>com.example.MyMainClass</mainClass>
    </configuration>
    <executions>
        <execution>
            <goals>
                <goal>pack-executable-jar</goal>
            </goals>
        </execution>
    </executions>
</plugin>

The built JAR file is located at target/<YourProjectAndVersion>-pkg.jar after you run mvn package. All of its compile-time and runtime dependencies will be included in the lib/ folder inside the JAR file.

Disclaimer: I am the author of the plugin.

edited Jun 04 '17 at 11:11

answered May 28 '17 at 10:16

Cybran

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I tried it and I can say it's working... As you said, this plugin creates a jar file, with its libraries (jars) into a lib directory in the jar... The configuration is really easy.. **I think it's what the author of this question is expecting** ... I will give you my vote up... The only drawback I have found on it (that´s the why I couldn´t use it), there is a delay when I execute my jar and the application is shown (about 20 secs) probably because of the process to register the libs in the custom classloader... But it´s a great approach and an excellent plugin... – Adam M. Gamboa G. Aug 06 '17 at 02:21
I am by no means an expert in maven, but I followed the instructions on the GitHub page and it doesn't work. And by doesn't work, I mean maven doesn't even acknowledge that it is in the pom file. I'm clueless. – bb121622 Oct 04 '20 at 00:12
It is well documented on the Github page, but perhaps you should mention that this requires code changes. The Maven plugin does the packaging, but to really make things work a custom classloader must be enabled at runtime. That may not be possible in all cases. Nice solution with that caveat. – ewramner May 10 '23 at 06:55

score 5 · Accepted Answer · edited May 23 '17 at 12:34

5

following this link:

How To: Eclipse Maven install build jar with dependencies

i found out that this is not workable solution because the class loader doesn't load jars from within jars, so i think that i will unpack the dependencies inside the jar.

edited May 23 '17 at 12:34

Community

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answered Aug 01 '12 at 13:48

Mahmoud Saleh

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score 3 · Answer 6 · answered Aug 01 '12 at 12:36

Here´s how I do it:

    <plugin>
            <artifactId>maven-assembly-plugin</artifactId>
            <version>2.2</version>
            <configuration>
                <appendAssemblyId>false</appendAssemblyId>
                <descriptorRefs>
                    <descriptorRef>jar-with-dependencies</descriptorRef>
                </descriptorRefs>
                <archive>
                    <manifest>
                        <mainClass>com.project.MainClass</mainClass>
                    </manifest>
                </archive>
            </configuration>
        </plugin>

And then I just run:

mvn assembly:assembly

Note that you should always do a compile before hand because `assembly` will just put whatever is in "target/classes" in the JAR. This will ensure that the JAR includes any changes you recently made to the source code. So, you should do something like: `mvn clean compile assembly:assembly`. — naXa stands with Ukraine, Sep 17 '14 at 10:30

score 2 · Answer 7 · answered Apr 21 '15 at 16:10

I found this answer to the question:

http://padcom13.blogspot.co.uk/2011/10/creating-standalone-applications-with.html

Not only do you get the dependent lib files in a lib folder, you also get a bin director with both a unix and a dos executable.

The executable ultimately calls java with a -cp argument that lists all of your dependent libs too.

The whole lot sits in an appasembly folder inside the target folder. Epic.

============= Yes I know this is an old thread, but it's still coming high on search results so I thought it might help someone like me.

score 1 · Answer 8 · answered Aug 01 '12 at 11:56

1

This is clearly a classpath problem. Take into consideration that the classpath must change a bit when you run your program outside the IDE. This is because the IDE loads the other JARs relative to the root folder of your project, while in the case of the final JAR this is usually not true.

What I like to do in these situations is build the JAR manually. It takes me at most 5 minutes and it always solves the problem. I do not suggest you do this. Find a way to use Maven, that's its purpose.

answered Aug 01 '12 at 11:56

Radu Murzea

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@SoboLAN Building the JAR manually is not a solution here. The intention is to use Maven, which is the exact opposite of "manual"! – Duncan Jones Aug 01 '12 at 11:59
@DuncanJones You are totally right. I do suggest he uses Maven to do it. However, I have no experience with it and didn't know exactly what solution to recommend. I edited my answer to reflect this. – Radu Murzea Aug 01 '12 at 12:01

How do I put all required JAR files in a library folder inside the final JAR file with Maven?

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