Maven compile mixed Java + Groovy 1.7 project, using gmaven-plugin

I had the same problem. I was missing the providerSelection configuration setting for 1.7.

Try this configuration and it should work for you.

  <plugin>
      <groupId>org.codehaus.gmaven</groupId>
      <artifactId>gmaven-plugin</artifactId>
      <version>1.2</version>
      <configuration> 
        <providerSelection>1.7</providerSelection> 
      </configuration> 
      <dependencies>
          <dependency>
            <groupId>org.codehaus.gmaven.runtime</groupId>
            <artifactId>gmaven-runtime-1.7</artifactId>
            <version>1.2</version>
            <exclusions>
              <exclusion>
                <groupId>org.codehaus.groovy</groupId>
                <artifactId>groovy-all</artifactId>
              </exclusion>
            </exclusions>
          </dependency>
          <dependency>
            <groupId>org.codehaus.groovy</groupId>
            <artifactId>groovy-all</artifactId>
            <version>1.7.0</version>
          </dependency>
      </dependencies>
      <executions>
          <execution>
              <goals>
                  <goal>generateStubs</goal>
                  <goal>compile</goal>
                  <goal>generateTestStubs</goal>
                  <goal>testCompile</goal>
              </goals>
          </execution>
      </executions>
  </plugin>