Мой Java EE proj работает нормально, но при попытке выполнить получаю следующее сообщение об ошибке:

gert@gert-VirtualBox:~/workspace/CDBOOKSTORE$ mvn exec:java 
[INFO] Scanning for projects... 
[INFO]                                       
[INFO] ------------------------------------------------------------------------
[INFO] Building CDBOOKSTORE 0.0.1-SNAPSHOT 
[INFO] ------------------------------------------------------------------------ 
[INFO]  
[INFO] >>> exec-maven-plugin:1.2.1:java (default-cli) @ CDBOOKSTORE >>>    
[INFO]  
[INFO] --- maven-dependency-plugin:2.8:copy (default) @ CDBOOKSTORE ---
[INFO]  
[INFO] < exec-maven-plugin:1.2.1:java (default-cli) @ CDBOOKSTORE <    
[INFO] 
[INFO] --- exec-maven-plugin:1.2.1:java (default-cli) @ CDBOOKSTORE ---
[INFO] ------------------------------------------------------------------------ 
[INFO] BUILD FAILURE 
[INFO] ------------------------------------------------------------------------ 
[INFO] Total time: 2.505s [INFO] Finished at: Fri Nov 08 14:01:40 EST 2013 
[INFO] Final Memory: 9M/21M 
[INFO] ------------------------------------------------------------------------    
[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.2.1:java (default-cli) on project CDBOOKSTORE: The parameters 'mainClass' for goal org.codehaus.mojo:exec-maven-plugin:1.2.1:java are missing or invalid
-> [Help 1]