concept Reverse Ajax in category java

This is an excerpt from Manning's book Portlets in Action. Login to get full access to this book.

Portlets that show real-time data should get their data from the data sources every time the render request is received by the portlet container. It would be bad design to use data caching in such scenarios, unless the data cache is actively synched with the data source holding the real-time data. Chapter 12 shows how Comet (or Reverse Ajax) can be used to push data from the server to create a portlet which shows real-time data.

At the end of the chapter, we’ll also look at the emerging Comet (or Reverse Ajax) and the traditional polling approach to creating portlets that display real-time data. We’ll look at how the Book Catalog portlet example uses Comet to notify users every time a book is added or removed from the catalog.

Listing 12.23. JavaScript in home.jsp that begins Reverse Ajax