Running Maven Exec Plugin Inside Eclipse

There's slight mistake in the pom.xml entry given by @grin. The correct one should be as follows:

<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>exec-maven-plugin</artifactId>
    <version>1.2.1</version>
    <executions>
        <execution>
           <goals>
            <goal>java</goal>
           </goals>
        </execution>
    </executions>
    <configuration>
        <mainClass>org.sonatype.mavenbook.weather.Main</mainClass>
    </configuration>
</plugin>

1. go to Run menu -> run configurations
2. you should see a "Maven Build" item on the list of the left, double click it to create a new configuration of that type
3. name it as you want
4. browse workspace to select the base directory of your project
5. set exec:java as the goal, and exec.mainClass / yourClass as parameters.

This is how it looks on my set-up:

PD: if you have set the mainClass argument on the pom.xml, then the parameter from the execution will be disregarded.

In pom.xml set the target class:

<plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>exec-maven-plugin</artifactId>
            <version>1.2.1</version>
            <executions>
                <execution>
                    <goals>
                        <goal>java</goal>
                    </goals>
                <configuration>
                       <mainClass>org.sonatype.mavenbook.weather.Main</mainClass>
                </configuration>
                </execution>
            </executions>

Then go to "Run as.. " -> "Maven build..." -> Goals "exec:java"