Struts, Trubine, Velocity, Expresso

[Muhammad Aamir]

     Hi,
     
     I recently explored the Struts Application framework features and 
     developed an small application using Struts.
     
     Recently I heard about other frameworks like Trubine, Velocity and 
     Expresso. I am really confused about what to choose and what is the 
     difference between these frameworks.
     
     Can anybody explain these frameworks and their differences ?
     
     
     
     Thanks in advance
     Muhammed Aamir