Maven jar Plugin

External

• http://maven.apache.org/plugins/maven-jar-plugin/

Internal

• Maven

Plugin Options

forceCreation

If set to true, the jar plugin will build a new JAR even if none of the contents appear to have changed. By default, this plugin looks to see if the output jar exists and inputs have not changed. If these conditions are true, the plugin skips creation of the jar.

Declaring a Main Class in JAR

      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-jar-plugin</artifactId>
        <version>3.0.2</version>
        <configuration>
          <archive>
            <manifest>
              <addClasspath>true</addClasspath>
              <mainClass>fully.qualified.MainClass</mainClass>
            </manifest>
          </archive>
        </configuration>
      </plugin>

Other Manifest Customization

Adding arbitrary manifest entries:

<plugin>
   <groupId>org.apache.maven.plugins</groupId>
   <artifactId>maven-jar-plugin</artifactId>
   <configuration>
      <archive>
         <manifest>
            <mainClass>io.novaordis.eventagent.EventAgent</mainClass>
         </manifest>
         <manifestEntries>
            <Premain-Class>io.novaordis.eventagent.EventAgent</Premain-Class>
            <Agent-Class>io.novaordis.eventagent.EventAgent</Agent-Class>
            <Can-Redefine-Classes>true</Can-Redefine-Classes>
            <Can-Retransform-Classes>true</Can-Retransform-Classes>
         </manifestEntries>
      </archive>
   </configuration>
</plugin>

In general, to use arbitrary manifest entries, use the following syntax:

...
<manifest>
</manifest>
<manifestEntries>
   ...
   <key>value</key>
   ...
</manifestEntries>

Include Dependencies - or Some of the Dependencies - in JAR

There are situations when we want to extract some of the dependencies and bundle them with the JAR artifact. This is done using the jar plugin and the dependency plugin together, as described here:

Include Dependencies in JAR Artifact

Explicitly Include Content in the JAR

http://maven.apache.org/plugins/maven-jar-plugin/examples/include-exclude.html

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-jar-plugin</artifactId>
  <version>3.0.2</version>
  <configuration>
    <includes>
      <include>**/service/*</include>
    </includes>
    <excludes>
      <exclude>**/something/*</exclude>
    </excludes>
  </configuration>
</plugin>

The patterns need to be relative to to the path specified for the plugin's classesDirectory parameter.