I would like to start/practice the the potal applications.Please help me what is the portal server that is in demand in the market(that helps me to get job easier) ?
please provide me link to jsr268 spec related tuorial/book links that I can start with?
To start with you need to understand the JSR specification. If you have knowledge and experience in J2EE then it should not take you long to understand Portlets.
Next thing is that just like Servlets need a Servlet Container to execute, similarly Portlets require a Portlet Container.
There are many different Portlet Containers available but few popular ones are provided by IBM, Liferay, JBoss. They provide Portal Servers.
Job wise currently the market is good for Liferay and IBM Websphere Portal servers.
You can visit the following URL to get more clarity and understand things. Let me know if I can be of more help.
Sun Certified Java Programmer v 1.4
Oracle Certified Associate, Java SE 7 Programmer
JEE 5 Web Component Developer Certified Professional