single sign on for different applications. in J2EE applications

i have 4 application and different technologies(php,.net and java) and 4 application having different database,and diff login page.

i want to create a login page so that all four application have only one login page and after the login from newly created page it skip login page of 4 application and next page after login must be displayed.

You should be looking at Single Sign On technologies.

SAML (security assertion markup language) is one ingredient technology that could solve such requirements. You would have a portal acting as a SAML Identity Provider, and your applications become SAML Service Providers. Many open source and commercial products are available that implement SAML that can help you integrate it.

Set a cookie from one of your application and check from the other applications whether the cookie is set for the correct domain. You can set the cookies value as the the currently logged in username.

So other applications can "trust" that and bypass login.

This is how we achieved single signon between our app and IBM Cognos.

Checkout this discussion for more details. - SSO between Java EE and Cognos application