Develop Reference

add build tasks to maven pom project

An existing maven pom project <packaging>pom</packaging> which currently collects and packages resources needs to be extended to validate some of the resources.
In the same project I created a java-source directory src/main/java and in there I created a small java class to validate some of the resources. In addition I configured the maven-compiler and exec-maven plugin in the pom.
The java class runs fine in the IDE but it fails when I do mvn clean install it fails because it cant find the compiled class file. This is because the compile/test-compile phase is not available for pom-packaged projects.
My questions are:
Can I modify the compiler plugin to execute (compile) in a different phase than the default compile-phase. (I tried with adding an execution tag but no success)
Why is the exec-maven plugin executed because this was defined in test phase, which according to the docs is not part of the pom-package.
Are there other possibilities to run this validation task in the pom?
Modifying the packaging from pom to jar is a political sub-optimal solution.

Yes, you can configure maven-compiler-plugin to run the compilation in the package phase of the pom packaging.
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.5.1</version>
<executions>
<execution>
<goals>
<goal>compile</goal>
</goals>
<phase>package</phase>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.4.0</version>
<executions>
<execution>
<goals>
<goal>java</goal>
</goals>
<phase>package</phase>
</execution>
</executions>
<configuration>
<mainClass>com.example.validate.App</mainClass>
</configuration>
</plugin>
</plugins>
</build>

Maven - how to rebuild a git revision number module on any module's build

I'm kinda new to maven and have encountered a problem that I can't solve on my own.
I've written a simple module to a big project that tracks git revision number, adds a timestamp and dumps these properties to a .properties file. This project is just a pom.xml file, no java classes, and one project.properties file. I wanted to add this module as a dependency to the main project pom.xml file, but it is rebuild only once (since Maven doesn't detect any changes it doesn't rebuild it again).
How do I force rebuild of this module everytime any module of the project is rebuilt? Can I do this in the project pom.xml file, or do I somehow set this in Jenkins? Or maybe I've approached this problem in a completely wrong way?
Here's the fragment of my pom.xml file:
<build>
<plugins>
<!-- enable ${timestamp} variable -->
<plugin>
<groupId>com.keyboardsamurais.maven</groupId>
<artifactId>maven-timestamp-plugin</artifactId>
<version>1.0</version>
<configuration>
<propertyName>timestamp</propertyName>
<timestampPattern>dd.MM.yyyy HH:mm</timestampPattern>
</configuration>
<executions>
<execution>
<goals>
<goal>create</goal>
</goals>
</execution>
</executions>
</plugin>
<!-- enable JGit plugin -->
<plugin>
<groupId>ru.concerteza.buildnumber</groupId>
<artifactId>maven-jgit-buildnumber-plugin</artifactId>
<version>1.2.7</version>
<executions>
<execution>
<id>git-buildnumber</id>
<goals>
<goal>extract-buildnumber</goal>
</goals>
<phase>initialize</phase>
</execution>
</executions>
</plugin>
<!-- write project properties to file -->
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>properties-maven-plugin</artifactId>
<version>1.0-alpha-2</version>
<executions>
<execution>
<phase>prepare-package</phase>
<goals>
<goal>write-project-properties</goal>
</goals>
<configuration>
<outputFile>${basedir}/target/classes/project.properties</outputFile>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
Cheers,
Jony

Okay, problem solved (thanks to deng from #maven on irc.codehaus.org). Right now i have the main pom and two modules: version-tracker and common. In the main pom I make a dependency on version-tracker, and in the common module's pom I add main pom as a parent (therefore common inherits dependency on version-tracker).
At this stage I run mvn clean package -pl :common -am and my project.properties file is updated every time. Thanks, deng :)
I still have some other problems, but this one is solved :)

Maven deploy jar with dependencies to repo

I can deploy a jar by using the following in my pom.xml and running mvn deploy:
<distributionManagement>
<repository>
<id>releases</id>
<url>http://${host}:8081/nexus/content/repositories/releases</url>
</repository>
<snapshotRepository>
<id>snapshots</id>
<name>Internal Snapshots</name>
<url>http://${host}:8081/nexus/content/repositories/snapshots</url>
</snapshotRepository>
</distributionManagement>
And I can build an executable jar-with-dependencies using the following:
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<executions>
<execution>
<id>create-executable-jar</id>
<phase>deploy</phase>
<goals>
<goal>single</goal>
</goals>
<configuration>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
<archive>
<manifest>
<mainClass>my.company.app.Main</mainClass>
</manifest>
</archive>
</configuration>
</execution>
</executions>
</plugin>
Problem is I don't know how to stitch these together to deploy the executable jar to my Maven repo. I don't really know if this is accomplished by a new plugin or by adding a goal or other step to the existing assembly plugin.

If you bind the assembly to the packaging phase, it will install in your repository both the "regular" jar and the with-dependencies jar when you do a build:
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<configuration>
<archive>
<manifest>
<mainClass>my.company.app.Main</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>
Then simply run mvn clean install deploy to upload both jars to your repository.

In order to build a (so-called) Über JAR and deploy it using maven, you could also use the shade plugin. The following code is taken from their website but I've made one or two projects using this feature.
<project>
...
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<version>2.0</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
<configuration>
<shadedArtifactAttached>true</shadedArtifactAttached>
<shadedClassifierName>jackofall</shadedClassifierName> <!-- Any name that makes sense -->
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
...
</project>
In this configuration you get the Über JAR as one deployment besides the normal JAR. The user of your JAR can then decide to pull the all-in-one package or the JAR with dependencies based on the classifier.
I'll usually use the shade plugin to build Über JARs (or modify the JAR in a way) and use the assembly plugin to build things like installation packages (containing the JAR and possibly other things). I am unsure what the intended goals of the single plugins are however.

The following worked. I'm going to leave this question open a bit because I'm not positive this is best practice, but working is something.
Problems I notice are that I made up the ID name and I don't know if this is usual practice and that I have to hard code the jar name; it isn't inferred from anything else.
<plugin>
<artifactId>maven-deploy-plugin</artifactId>
<version>2.7</version>
<executions>
<execution>
<id>deploy-executable</id>
<goals>
<goal>deploy-file</goal>
</goals>
<configuration>
<file>target/Monitoring-Client-1.0-SNAPSHOT-jar-with-dependencies.jar</file>
</configuration>
</execution>
</executions>
</plugin>

Essentially my difficulty doing this revealed the fact that my pom.xml was way off the rails already. Everything would have snapped into place on its own. I was formerly doing:
Save all the dependencies into a lib folder
Build a jar with a classpath slurping up that lib folder
Use the assembly plugin to make another deployable jar
I think there were several reasons this sort of made sense along the way, especially when my libraries were not well-factored from my applications.
However by deleting 1 and 2 all that is needed is the distributionManagement section and the deploy phase works automagically. So all in all this is an amazing case of literally adding functionality by deleting large swathes of code.

First you shouldn't do the creation of the ueber jar in the deploy phase it's better to do this in the package phase. Furthermore the created jar file is usually automatically attached to your artifact and will be transfered to the remote repository (in your case Nexus). You can check this if you simply try to do a mvn install and take a look at the output if the created jar is installed into the local repository.
To deploy the results into nexus you need to call mvn deploy.

how to use class file from another war

We have two different web application and we want to extend few controllers of one war into another war.
We are using maven to build the project.
to include war we have given its dependency as
<dependency>
<groupId>com.abc.exchange</groupId>
<artifactId>employer</artifactId>
<version>2.3.M2-SNAPSHOT</version>
<type>war</type>
<scope>compile</scope>
</dependency>
It is unable to build giving class not found exception.
Can any body help me out how to achieve this?
I am getting error maven build failed :
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.3.2:compile (default-compile) on project agent-war: Compilation failure: Compilation failure:
[ERROR] \projects\trunk_new\agent\src\main\java\com\platform\agent\web\AgentEmployeeController.java:[22,41] cannot find symbol
[ERROR] symbol : class EmployeeController
[ERROR] location: package com..platform.employer.web

You can define the war plugin to produce a separate jar file which is available via a classifier based on the configuration:
<configuration>
..
<attachClasses>true</attachClasses>
<archiveClasses>true</archiveClasses>
</configuration>
After that you can use this as a separate dependency in other projects. But the best to make a separate jar module out of it.

What you are doing is using a WAR file overlay. Maven does support this. However...
The WAR plugin executes in the package phase. Any plugin, such as the Java compiler (which runs in the compile phase), that executes before this phase will not see any files that the WAR plugin has extracted. (here is the reference list of all Maven phases if that helps)
If you have the ability to refactor your project structure, the best way is to create a normal JAR project with your controllers and have both WARs pull this JAR in as a dependency.
If there is some reason why you can't do this, you will need to do something like:
Configure the WAR plugin to run in a phase earlier than compile, such as generate-resources and makes sure it extracts the overlay class files to ${project.build.outputDirectory}.
You could also use the Maven Dependency Plugin's unpack goal to extract classes from the dependency WAR to ${project.build.outputDirectory}.
But I do recommend if at all possible to refactor your controllers into a separate JAR, it is much easier and more maintainable.

put the controllers into a new jar project and make dependencies from your webprojects to this controllers.

Add the following plugins to your share maven war module (for creating war and jar artifact at the same time):
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.4</version>
<executions>
<execution>
<id>make-a-jar</id>
<phase>compile</phase>
<goals>
<goal>jar</goal>
</goals>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-install-plugin</artifactId>
<version>2.4</version>
<executions>
<execution>
<phase>install</phase>
<goals>
<goal>install-file</goal>
</goals>
<configuration>
<packaging>jar</packaging>
<artifactId>${project.artifactId}</artifactId>
<groupId>${project.groupId}</groupId>
<version>${project.version}</version>
<file>
${project.build.directory}/${project.artifactId}-${project.version}.jar
</file>
</configuration>
</execution>
</executions>
</plugin>
then add dependency to your dependent maven war module.

Java EE visability standards state that classes from one war shouldn't be available to classes in another war, when they're packaged as an EAR. Most containers will enforce this strictly.
You should put the code you wish to share into a JAR and include that as a dependency in the war you want to use.

In the war project pom.xml include
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>2.1.1</version>
<configuration>
<attachClasses>true</attachClasses>
</configuration>
</plugin>
This will create your-project-0.0.1-SNAPSHOT-clases.jar in the target folder along with the war.
In the dependent project pom.xml include
<dependency>
<groupId>com.yourproject</groupId>
<artifactId>you-project</artifactId>
<version>0.0.1-SNAPSHOT</version>
<classifier>classes</classifier>
</dependency>
This worked for me. Hope it helps.
Edit: If we want only some class files into the jar then add this to pom.xml
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.4</version>
<executions>
<execution>
<id>make-a-jar</id>
<phase>compile</phase>
<goals>
<goal>jar</goal>
</goals>
<configuration>
<classifier>classifier_name</classifier>
<includes>
<include>com/../..</include>
</includes>
</configuration>
</execution>
</executions>
</plugin>
In the dependent project pom.xml include
<dependency>
<groupId>com.yourproject</groupId>
<artifactId>you-project</artifactId>
<version>0.0.1-SNAPSHOT</version>
<classifier>classifier_name</classifier>
</dependency>
note: the classifier name must be same in both pom.xml files

Make Maven to copy dependencies into target/lib

How do I get my project's runtime dependencies copied into the target/lib folder?
As it is right now, after mvn clean install the target folder contains only my project's jar, but none of the runtime dependencies.

This works for me:
<project>
...
<profiles>
<profile>
<id>qa</id>
<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>
</profile>
</profiles>
</project>

mvn install dependency:copy-dependencies
Works for me with dependencies directory created in target folder. Like it!

The best approach depends on what you want to do:
If you want to bundle your dependencies into a WAR or EAR file, then simply set the packaging type of your project to EAR or WAR. Maven will bundle the dependencies into the right location.
If you want to create a JAR file that includes your code along with all your dependencies, then use the assembly plugin with the jar-with-dependencies descriptor. Maven will generate a complete JAR file with all your classes plus the classes from any dependencies.
If you want to simply pull your dependencies into the target directory interactively, then use the dependency plugin to copy your files in.
If you want to pull in the dependencies for some other type of processing, then you will probably need to generate your own plugin. There are APIs to get the list of dependencies, and their location on disk. You will have to take it from there...

Take a look at the Maven dependency plugin, specifically, the dependency:copy-dependencies goal. Take a look at the example under the heading The dependency:copy-dependencies mojo. Set the outputDirectory configuration property to ${basedir}/target/lib (I believe, you'll have to test).
Hope this helps.

All you need is the following snippet inside pom.xml's build/plugins:
<plugin>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<phase>prepare-package</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
<configuration>
<outputDirectory>${project.build.directory}/lib</outputDirectory>
</configuration>
</execution>
</executions>
</plugin>
The above will run in the package phase when you run
mvn clean package
And the dependencies will be copied to the outputDirectory specified in the snippet, i.e. lib in this case.
If you only want to do that occasionally, then no changes to pom.xml are required. Simply run the following:
mvn clean package dependency:copy-dependencies
To override the default location, which is ${project.build.directory}/dependencies, add a System property named outputDirectory, i.e.
-DoutputDirectory=${project.build.directory}/lib

If you want to do this on an occasional basis (and thus don't want to change your POM), try this command-line:
mvn dependency:copy-dependencies -DoutputDirectory=${project.build.directory}/lib
If you omit the last argument, the dependences are placed in target/dependencies.

A simple and elegant solution for the case where one needs to copy the dependencies to a target directory without using any other phases of maven (I found this very useful when working with Vaadin).
Complete pom example:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>groupId</groupId>
<artifactId>artifactId</artifactId>
<version>1.0</version>
<dependencies>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis-spring</artifactId>
<version>1.1.1</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<phase>process-sources</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
<configuration>
<outputDirectory>${targetdirectory}</outputDirectory>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
Then run mvn process-sources
The jar file dependencies can be found in /target/dependency

Try something like this:
<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>
<mainClass>MainClass</mainClass>
</manifest>
</archive>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<version>2.4</version>
<executions>
<execution>
<id>copy</id>
<phase>install</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
<configuration>
<outputDirectory>
${project.build.directory}/lib
</outputDirectory>
</configuration>
</execution>
</executions>
</plugin>

supposing
you don't want to alter the pom.xml
you don't want test scoped (e.g. junit.jar) or provided dependencies (e.g. wlfullclient.jar)
here ist what worked for me:
mvn install dependency:copy-dependencies -DincludeScope=runtime -DoutputDirectory=target/lib

If you want to deliver a bundle of your application jar, together with all its dependencies and some scripts to invoke the MainClass, look at the appassembler-maven-plugin.
The following configuration will generate scripts for Window and Linux to launch the application (with a generated path referencing all the dependency jars, download all dependencies (into a lib folder below target/appassembler). The assembly plugin can then be used to package the whole appassembler directory to a zip which is installed/deployed along with the jar to the repository.
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>appassembler-maven-plugin</artifactId>
<version>1.0</version>
<executions>
<execution>
<id>generate-jsw-scripts</id>
<phase>package</phase>
<goals>
<goal>generate-daemons</goal>
</goals>
<configuration>
<!--declare the JSW config -->
<daemons>
<daemon>
<id>myApp</id>
<mainClass>name.seller.rich.MyMainClass</mainClass>
<commandLineArguments>
<commandLineArgument>start</commandLineArgument>
</commandLineArguments>
<platforms>
<platform>jsw</platform>
</platforms>
</daemon>
</daemons>
<target>${project.build.directory}/appassembler</target>
</configuration>
</execution>
<execution>
<id>assemble-standalone</id>
<phase>integration-test</phase>
<goals>
<goal>assemble</goal>
</goals>
<configuration>
<programs>
<program>
<mainClass>name.seller.rich.MyMainClass</mainClass>
<!-- the name of the bat/sh files to be generated -->
<name>mymain</name>
</program>
</programs>
<platforms>
<platform>windows</platform>
<platform>unix</platform>
</platforms>
<repositoryLayout>flat</repositoryLayout>
<repositoryName>lib</repositoryName>
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<version>2.2-beta-4</version>
<executions>
<execution>
<phase>integration-test</phase>
<goals>
<goal>single</goal>
</goals>
<configuration>
<descriptors>
<descriptor>src/main/assembly/archive.xml</descriptor>
</descriptors>
</configuration>
</execution>
</executions>
</plugin>
The assembly descriptor (in src/main/assembly) to package the direcotry as a zip would be:
<assembly>
<id>archive</id>
<formats>
<format>zip</format>
</formats>
<fileSets>
<fileSet>
<directory>${project.build.directory}/appassembler</directory>
<outputDirectory>/</outputDirectory>
</fileSet>
</fileSets>
</assembly>

If you make your project a war or ear type maven will copy the dependencies.

It's a heavy solution for embedding heavy dependencies, but Maven's Assembly Plugin does the trick for me.
#Rich Seller's answer should work, although for simpler cases you should only need this excerpt from the usage guide:
<project>
<build>
<plugins>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<version>2.2.2</version>
<configuration>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
</plugin>
</plugins>
</build>
</project>

You can use the the Shade Plugin to create an uber jar in which you can bundle all your 3rd party dependencies.

Just to spell out what has already been said in brief. I wanted to create an executable JAR file that included my dependencies along with my code. This worked for me:
(1) In the pom, under <build><plugins>, I included:
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<version>2.2-beta-5</version>
<configuration>
<archive>
<manifest>
<mainClass>dk.certifikat.oces2.some.package.MyMainClass</mainClass>
</manifest>
</archive>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
</plugin>
(2) Running mvn compile assembly:assembly produced the desired my-project-0.1-SNAPSHOT-jar-with-dependencies.jar in the project's target directory.
(3) I ran the JAR with java -jar my-project-0.1-SNAPSHOT-jar-with-dependencies.jar

If you're having problems related to dependencies not appearing in the WEB-INF/lib file when running on a Tomcat server in Eclipse, take a look at this:
ClassNotFoundException DispatcherServlet when launching Tomcat (Maven dependencies not copied to wtpwebapps)
You simply had to add the Maven Dependencies in Project Properties > Deployment Assembly.

You could place a settings.xml file in your project directory with a basic config like this:
<?xml version="1.0" encoding="UTF-8"?>
<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0 https://maven.apache.org/xsd/settings-1.0.0.xsd">
<localRepository>.m2/repository</localRepository>
<interactiveMode/>
<offline/>
<pluginGroups/>
<servers/>
<mirrors/>
<proxies/>
<profiles/>
<activeProfiles/>
</settings>
More information on these settings can be found in the official Maven docs.
Note that the path is resolved relative to the directory where the actual settings file resides in unless you enter an absolute path.
When you execute maven commands you can use the settings file as follows:
mvn -s settings.xml clean install
Side note: I use this in my GitLab CI/CD pipeline in order to being able to cache the maven repository for several jobs so that the dependencies don't need to be downloaded for every job execution. GitLab can only cache files or directories from your project directory and therefore I reference a directory wihtin my project directory.