Make Eclipse Respect Maven-Dependency-Plugin - eclipse

Question

How can I have Eclipse recognise my use of the maven-dependency-plugin and execute it before deploying resources to Tomcat via WTP?
In a previous question I configured Maven to copy some artifacts into a war application, so I could serve them to web clients. The approach of copying them to target/${project.artifactId}-${project.version} works when packaging via the Maven command line. Sadly there's no such luck when using Eclipse's Tomcat integration.
Maven plugin configuration:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<version>2.8</version>
<executions>
<execution>
<id>copy</id>
<phase>compile</phase>
<goals>
<goal>copy</goal>
</goals>
<configuration>
<artifactItems>
<artifactItem>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<type>jar</type>
<overWrite>false</overWrite>
<destFileName>optional-new-name.jar</destFileName>
</artifactItem>
</artifactItems>
<outputDirectory>${project.build.directory}/${project.artifactId}-${project.version}/</outputDirectory>
<overWriteReleases>false</overWriteReleases>
<overWriteSnapshots>true</overWriteSnapshots>
</configuration>
</execution>
</executions>

Answer 1

This answer assumes you're using Eclipse Java EE Kepler SR1 (or more recent), which comes with the Maven integration plugins (m2e and m2e-wtp).
m2e-wtp, the Maven Integration for WTP plugin ignores maven CLI builds and configures WTP to publish resources from known locations.
So you need to do 2 things :
configure the dependency plugin to copy jars to a known m2e-wtp location during eclipse builds
tell m2e to actually run the dependency plugin during project configuration updates.
First, define a new maven property, in your properties section :
<jars.directory>${project.build.directory}/${project.artifactId}-${project.version}/</jars.directory>
In your maven-dependency-plugin configuration, use :
<outputDirectory>${jars.directory}</outputDirectory>
Now that should give you identical build results with Maven CLI. Then you need to use a specific m2e profile, that'll be automatically enabled when run in Eclipse and ignored in all other situations :
<profiles>
<profile>
<id>m2e</id>
<!-- This profile is only activated when building in Eclipse with m2e -->
<activation>
<property>
<name>m2e.version</name>
</property>
</activation>
<properties>
<jars.directory>${project.build.directory}/m2e-wtp/web-resources/</jars.directory>
</properties>
</profile>
</profiles>
Finally, we need to let m2e know it's ok to run maven-dependency-plugin:copy during project configuration. Add the following snippet to your pluginManagement section :
<pluginManagement>
<plugins>
<!--This plugin's configuration is used to store Eclipse m2e settings
only. It has no influence on the Maven build itself. -->
<plugin>
<groupId>org.eclipse.m2e</groupId>
<artifactId>lifecycle-mapping</artifactId>
<version>1.0.0</version>
<configuration>
<lifecycleMappingMetadata>
<pluginExecutions>
<pluginExecution>
<pluginExecutionFilter>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<versionRange>[2.8,)</versionRange>
<goals>
<goal>copy</goal>
</goals>
</pluginExecutionFilter>
<action>
<execute>
<runOnConfiguration>true</runOnConfiguration>
<runOnIncremental>false</runOnIncremental>
</execute>
</action>
</pluginExecution>
</pluginExecutions>
</lifecycleMappingMetadata>
</configuration>
</plugin>
</plugins>
</pluginManagement>
Now, make sure m2e knows about all these configuration changes : Hit Alt+F5 to bring up the Update Maven Configuration dialog, and click ok. Once the build completes, you should see your jar under Deployed Resources> web-resources, in the Project Explorer view.
From now on, deployments to Tomcat should contain optional-new-name.jar at the root of your webapp.