And I guess we will map Servlet mapping in web.xml and prweb is a war file I guess not xml file. Please correct me If I'm wrong and Also please help me to set up SSO.

Yes I meant the web.xml inside the prweb not the tomcat one.

As per my knowledge we will configure LDAP using custom authentication Service where as for SSO we will use SAML 2.0 as Authentication type.

Both can be used for SSO , to use LDAP you need to select custom type whereas SAML2.0 for SAML. These are 2 different ways of achieving SSO where IDP will handle the authentication part instead of your own database. 

The idea behind Single Sign-On is that users can use an "external" set of credentials, in this case from Active Directory, to authenticate against your application.

In practice, that "external" user ultimately maps to an internal account (a generic account, like "user") that has the correct permissions.

What SAML does is actually pass session tokens around. User credentials are passed to a token, and then that token is authenticated against the "user" account.

LDAPS would skip all that token stuff and just authenticate directly against "user". This means there's no session security, users stay authenticated forever.

I think you should first understand the difference bw LDAP and SAML . Read some documents of what LDAP and SAML does before setting it up. It will help you in understanding what both does.

There are other authentications like OAuth and Kerberos. But the way of authenticating user is different. Some are tokens based, some are session token based and some are directly authenticating from their server.

Thank you

-abhishek