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Maven

Update Parent POM Version in Modules

If the project structure is the following:

 Parent POM
     +
     |
     +---> Module 1
     |
     +---> Module 2
     |
     +---> Module 3

and the modules inherit the version from the parent pom then it is a PITA to update all modules with the new parent pom version when the parent pom version is incremented.

An easy way for this is the following command which will update the parent pom version in the modules with the version in the parent pom project.

mvn -N versions:update-child-modules

By default this command will generate a backup version of each updated pom. To drop the generation of backups add the parameter generateBackupPoms=false to the maven command.

Found on Mojohaus.org.

Manifest.merge Error in Eclipse

org.codehaus.plexus.archiver.jar.Manifest.merge(org.codehaus.plexus.archiver.jar.Manifest)

This error only occurs in Eclipse. The Eclipse Plugin for the Maven Archiver needs to be updated with this update site:

http://repo1.maven.org/maven2/.m2e/connectors/m2eclipse-mavenarchiver/0.17.0/N/LATEST/

See http://stackoverflow.com/questions/28351678/org-codehaus-plexus-archiver-jar-manifest-mergeorg-codehaus-plexus-archiver-jar

Copy Maven Artifact on Build

<build>
	<plugins>
		<plugin>
			<groupId>org.codehaus.mojo</groupId>
			<artifactId>wagon-maven-plugin</artifactId>
			<version>1.0-beta-5</version>
			<executions>
				<execution>
					<id>upload-jar-to-folder</id>
					<phase>deploy</phase>
					<goals>
						<goal>upload</goal>
					</goals>
				</execution>
			</executions>
			<configuration>
				<fromDir>${project.build.directory}</fromDir>
				<includes>${project.build.finalName}.${project.packaging}</includes>
				<url>file:///opt/karaf</url>
				<toDir>deploy</toDir>
			</configuration>
		</plugin>
	</plugins>
</build>

Add 3rd Party Library

Sometimes a 3rd party Java library is needed in a Maven project. But the 3rd party jar is not a Maven artifact. Maven has a command for adding those jars to your local repo.

mvn install:install-file -Dfile=/tmp/jtopen.jar \
    -DgroupId=jtopen \
    -DartifactId=jtopen \
    -Dversion=7.10 \
    -Dpackaging=jar

Skip Unit test

%%-Dmaven.test.skip=true%%

Embed Dependencies

If all dependencies should be embedded into one jar then the Maven Bundle Plugin can be used. All dependencies which should be installed as their own bundle should be configured as scope: provided. All dependencies which should be embedded should be configured as scope: compile.

<Embed-Dependency>*;scope=compile</Embed-Dependency>

To embed all transitive dependencies the following configuration must be added to the pom.xml:

<Embed-Transitive>true</Embed-Transitive>

The Maven Bundle Plugin embeds all configured dependencies and adjusts the Bundle-ClassPath in the Manifest file.

Example

  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.felix</groupId>
        <artifactId>maven-bundle-plugin</artifactId>
        <configuration>
          <instructions>
            <Embed-Dependency>*;scope=compile</Embed-Dependency>
            <Embed-Transitive>true</Embed-Transitive>
          </instructions>
        </configuration>
      </plugin>
    </plugins>
  </build>

Exec Maven Plugin

Using the exec-maven-plugin a Java application can be executed with maven from the command line.

  <plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>exec-maven-plugin</artifactId>
    <version>1.2.1</version>
    <configuration>
        <mainClass>de.sgbs.xeno.klax.ImportApp</mainClass>
        <arguments>
            <argument>-i</argument>
            <argument>${input.file}</argument>
        </arguments>
    </configuration>
  </plugin>

Maven Goals

  • exec:exec execute programs and Java programs in a separate process.
  • exec:java execute Java programs in the same VM.

Executing Java Program with Test Resources

mvn exec:java -Dexec.classpathScope="test"

Passing arguments

Arguments can be passed to the maven via the Java environment variables (-D arguments).

mvn exec:java -Dinput.file="my_file.txt"

The Java environment variables can be used in maven as a normal variable, like ${var}.

Passing arguments to main class

Arguments of the main class can be passed with the exec.args Java environment variable.

mvn exec:java -Dexec.args="these arguments are passed to the main class"
maven.1464341751.txt.gz · Last modified: 2016/05/27 09:35 by mihael