I have an application that do motly excel parsing. It is currently written in jsp+ servlets. Can you guide me how to migrate my application in grails. One of the problems I see is the excel part. DOes grails have API in Excel files processing. Getting the number of sheets for example, using ajax to prompt the user the available sheet names. Something like that. I hope you can give me at least an overview or a step by step guide. Thanks.
Why do you want to migrate ? Grails is a domain model centric framework. From your description it does not look like your application has much of a domain model. In case you just want to dabble in the technology, see getting started guide on groovy site or you can follow "Mastering Grails" series on IBM developerworks site
Groovy is build on Java, and can use existing Java libraries. So if you currently have servlets and JSPs that use a Java API to process Excell documents, then you can do the same with Groovy. Look in the Groovy documentation on how to access Java classes. (Grails is basically a web framework for Groovy.)