Execute a task in Maven before packaging - eclipse

Question

I don't understand how to run a task in Maven, before packaging.
<build>
<plugins>
[...]
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-antrun-plugin</artifactId>
<version>1.7</version>
<executions>
<execution>
<phase>generate-sources</phase>
<configuration>
<tasks>
<echo message="****** TEST *****" />
</tasks>
</configuration>
</execution>
</executions>
</plugin>
When I run mvn clean package, it doesn't get executed. How can I have this task executed? I'm using maven 3.0.5, if it matters.
** UPDATE: **
Adding id and goal as suggested, solved the problem from the command line.
<id>my-generate-sources</id>
<goals>
<goal>run</goal>
</goals>
To fix Eclipse error, I've configured lifecyleMappingMetadata, within the build section:
<build>
...
<pluginManagement>
<plugins>
<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-antrun-plugin</artifactId>
<versionRange>[1.7,)</versionRange>
<goals>
<goal>run</goal>
</goals>
</pluginExecutionFilter>
<action>
<execute />
</action>
</pluginExecution>
</pluginExecutions>
</lifecycleMappingMetadata>
</configuration>
</plugin>
</plugins>
</pluginManagement>

Answer 1

You need to add the <goals> tag (and adding an <id> tag is also strongly encouraged though not required if you only have one <execution> for the plugin), e.g.
...
<execution>
<id>print-something</id>
<phase>generate-sources</phase>
<goals>
<goal>run</goal>
</goals>
<configuration>
<tasks>
<echo message="****** TEST *****" />
</tasks>
</configuration>
</execution>
...

Answer 2

Try adding an execution id:
<execution>
<phase>generate-sources</phase>
<id>my-generate-sources</id>
<configuration>
<tasks>
<echo message="****** TEST *****" />
</tasks>
</configuration>
<goals>
<goal>run</goal>
</goals>
</execution>
UPDATE
I forgot the run goal, as Guillame said. Eclipse maven integration is one of the worse things I have ever seen. The way we were running it is exclusivley via maven command line, and that is what I would recommend. You can still run it from eclipse like this:
create a new empty project
create mvn-clean-package.launch file in it
The file should look like this:
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<launchConfiguration type="org.eclipse.ui.externaltools.ProgramLaunchConfigurationType">
<stringAttribute key="org.eclipse.debug.core.ATTR_REFRESH_SCOPE" value="${resource}"/>
<listAttribute key="org.eclipse.debug.ui.favoriteGroups">
<listEntry value="org.eclipse.ui.externaltools.launchGroup"/>
</listAttribute>
<stringAttribute key="org.eclipse.ui.externaltools.ATTR_LAUNCH_CONFIGURATION_BUILD_SCOPE" value="${none}"/>
<stringAttribute key="org.eclipse.ui.externaltools.ATTR_LOCATION" value="/usr/bin/mvn"/>
<stringAttribute key="org.eclipse.ui.externaltools.ATTR_TOOL_ARGUMENTS" value="clean package -DskipTests=true -U"/>
<stringAttribute key="org.eclipse.ui.externaltools.ATTR_WORKING_DIRECTORY" value="${selected_resource_loc}"/>
</launchConfiguration>
As long as this project is opened in your workspace, you can select any other project folder that contains pom.xml and select your mvn-clean-package command from the external tools button:
This will run:
mvn clean package -DskipTests=true -U
from the selected folder. You can see the output in Eclipse console window.
The external tools are also accessible also from the Run menu. I suppose that there is method to achieve this through Eclipse UI, but I didn't use Eclipse long enough to find that out.