Maven: specify the outputDirectory only for packaging a jar? - maven-2

Question

How can I specify the outputDirectory only for packaging a jar?
http://maven.apache.org/plugins/maven-jar-plugin/jar-mojo.html this shows all parameters, but how can I set them in the commandline or pom.xml?

Answer 1

on command line
-DoutputDirectory=<path>
and in pom.xml
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.3.1</version>
<configuration>
<outputDirectory>/my/path</outputDirectory>
</configuration>
</plugin>
</plugins>
</build>

Answer 2

Parameter Expressions
About command line usage:
The parameter documentation specifies that the parameter is initialized to the value of the property ${project.build.directory} (which is the property referring to the target folder)
Here's what this means:
For mojos that are intended to be
executed directly from the CLI, their
parameters usually provide a means to
be configured via system properties
instead of a <configuration/> section
in the POM. The plugin documentation
for those parameters will list an
expression that denotes the system
properties for the configuration. In
the mojo above, the parameter url is
associated with the expression
${query.url}, meaning its value can be
specified by the system property
query.url as shown below:
mvn myquery:query -Dquery.url=http://maven.apache.org
Reference:
Guide to Configuring Plug-ins > Generic Configuration
Configuring ${project.build.directory}
However, ${project.build.directory} is not a system property, it's a property of the Project's Build object.
You can't set maven's internal properties directly on the command line, but you can get there with a little trick by adding placeholders in your pom.xml:
<build>
<directory>${dir}</directory>
</build>
Now, the output directory is set via the property from the command line (using -Ddir=somedirectory). Downside: now you always have to use the -Ddir parameter on the command line.
Using Profiles
But there's help here, too. Just use a profile when you want to configure the directory:
<profiles>
<profile>
<id>conf</id>
<build>
<directory>${dir}</directory>
</build>
</profile>
</profiles>
Now you can either do
# everything goes in someOtherDir instead of target
mvn clean install -Pconf -Ddir=someOtherDir
or plain old
# everything goes in target
mvn clean install
Configuring the Jar Plugin
Now if you just want to change the jar outputDirectory from the command line without redirecting everything from target, we'll modify the profile to configure the plugin from a command line property:
<profiles>
<profile>
<id>conf</id>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.3.1</version>
<configuration>
<outputDirectory>${dir}</outputDirectory>
</configuration>
</plugin>
</plugins>
</build>
</profile>
</profiles>
The usage is identical to above:
# everything goes in someOtherDir instead of target
mvn clean install -Pconf -Ddir=someOtherDir

Answer 3

Thanks #Sean Patrick Floyd for the excellent explanation.
Instead of creating a profile and using mvn always by -P switch, I'd like to use another way that making a default value of property ${dir}.
Just define ${dir}'s default value as ${project.build.directory}
<properties>
<dir>${project.build.directory}</dir>
</properties>
and same as #Sean Patrick Floyd, set outputDirectory.
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.3.1</version>
<configuration>
<outputDirectory>${dir}</outputDirectory>
</configuration>
</plugin>
</plugins>
Now you can either do
# everything goes in someOtherDir instead of target
mvn clean install -Ddir=someOtherDir
or plain old
# everything goes in target
mvn clean install

Answer 4

If you wish copy dependency jars as well to a target folder, use maven-dependency-plugin.
<project>
...
...
<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>
</project>