Develop Reference

Create a single jar containing dependencies and Javadoc with Maven

I'm trying to create a jar file with both Javadoc and dependencies that I can use in another project.
I can use mvn package with the following pom.xml plugins:
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-javadoc-plugin</artifactId>
<configuration>
<javadocExecutable>${java.home}/bin/javadoc</javadocExecutable>
</configuration>
<version>2.7</version>
<executions>
<execution>
<id>attach-javadoc</id>
<phase>prepare-package</phase>
<goals>
<goal>javadoc</goal>
</goals>
<configuration>
<destDir>docs</destDir>
<reportOutputDirectory>${project.build.directory}/classes/</reportOutputDirectory>
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<configuration>
<archive>
<manifest>
<mainClass>fully.qualified.MainClass</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>
This creates a Javadoc as well as add the Javadoc and the dependencies to a single jar. However, the Javadoc doesn't actually seem to work as when I hover over the Classes and Methods in Eclipse it says This element neither has attached source nor attached Javadoc and hence no Javadoc could be found.
When I export the jar using the eclipse exporter I can get the Javadoc to work but because my jar is not runnable I can't package it with my dependencies and so it doesn't actually work.
If anyone has any idea how I can get this to work, tell me why my understanding is flawed or can point me in the right direction I will be very appreciative.

Don't do that. Your library jar does not get to have opinions about which dependency versions to include and how. Let Maven do its job and pull them in transitively in the client projects. (Publish the Maven artifacts if that's the problem; it looks like you're trying to do this part manually.)
Also don't include Javadoc; it's not necessary at runtime and bulks up the deployment package unnecessarily.
Overall, when there's a Standard Way of doing things, it's usually there for a reason and best to go along with it, if for no other reason than that's what everyone you interact with expects.

Maven build appears to be overwriting classes when creating jar-with-dependencies

I'm using maven to build a jar-with-dependencies jar. One of the vendor jar files in the project has similarly named classes with different case. For example aM.class and am.class.
When the build creates the "jar-with-dependencies" jar file, only aM.class is present. am.class appears to have been overwritten or skipped. The same thing happens for every similarly named classes files.
We have a couple work-arounds, but I'm curious why the maven build is behaving this way. Thanks
My pom:
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<version>2.1</version>
<configuration>
<archive>
<manifest>
<mainClass>com.mytest.MyTest</mainClass>
</manifest>
</archive>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
<executions>
<execution>
<id>make-assembly</id>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
</execution>
</executions>
</plugin>
<dependencies>
<dependency>
<groupId>com.bloomberglp</groupId>
<artifactId>blpapi3</artifactId>
<version>3.10.1</version>
</dependency>
</dependencies>

Same class conflict issue will happen with maven-assembly-plugin, this plugin extracts all dependency jars into raw classes, and group it together.It works in project with less dependencies only, for large project with many dependencies, it will cause Java class name conflict issue, check here.
Better way to use maven-shade-plugin if you have many jars with potentially could conflict. You can also you relocating feature in shade plugin to explicitly avoid conflicts

How to configure Maven build for Java project with external dependencies?

I'm trying to create automated solution for building with maven. My vision is to have a Maven build, which creates JAR file from my project and then just copies all the dependencies as JARs to some sub-directory in "target" folder.
I do not want to use Shade or Assembly (so I do not want to extract the content of other JARs and include it in one "super-JAR", because the project is more complicated and it breaks when I'm including all the JARs in one file).
How can I do such build POM?

I don't see here any problem. Just create maven pom.xml with <packaging>jar</packaging>
By default it should not pack into your jar all dependent libraries.
<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>

Related with your latest comment, use this plugin to add the main class in the manifest:
<plugin>
<!-- Build an executable JAR -->
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<classpathPrefix>lib/</classpathPrefix>
<mainClass>com.test.YourMainClass</mainClass>
</manifest>
</archive>
</configuration>
</plugin>

You can use the maven-assembly-plugin to create a .zip file from a selection of other files in your directory. I have used this method to create distribution zip files for a project. There are several examples available in the maven-assembly-plugin documentation.

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.

maven-dependency-plugin generates duplicate files in jar-with-dependencies.jar file

i am creating a standalone java application with maven, and i am including the dependencies in the jar file with maven-dependecy-plugin as follows:
<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>theMainClass</mainClass>
</manifest>
</archive>
</configuration>
</plugin>
<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>
this includes the dependencies in the generated jar file in a lib folder, and the jar runs and works fine, but the issue is in the other generated jar file appname-1.0-jar-with-dependencies.jar.
ISSUE: i am not sure if it's an issue or not, but i noticed in target folder in the generated appname-1.0-jar-with-dependencies.jar, that it contains duplicate application files like:
all sql,property files,xml files exists twice.
all java classes .class file exists twice.
there are lots of overview.html and license.txt files related to the dependencies.
i am not sure if that's feels right or not, also i need someone to clarify for me what is the importance of this generated jar file, since i am not familiar with this plugin.
please advise, thanks.

Since you have mentioned jar-with-dependencies, I assume you are using maven assembly plugin to assemble your project artifacts along with the dependant jars into a single jar.
I suspect that your project artifacts are getting into the jar-with-dependencies twice - due to a property useProjectArtifact of dependencySet which is true, by default. You can set this property to true in your assembly descriptor and see if it addresses your issue.
In the specific case above, maven dependency plugin does not seem to be doing anything useful. maven assembly plugin automatically packages all its dependencies into a single distribution as per configuration.
But do note classpath issues if you create an executable jar-with-dependencies. You may want to create a zip or tar.gz instead.
The configuration used above is the default and does not allow for customization. You may want to use an assembly descriptor file, where you can set the property mentioned earlier or other options.