In my login page I log in through username and password (that I get from a jsp page), then I check LDAP and if the credentials are correct, then I continue the browsing to other
You should use different passwords for your web application and LDAP. Like now, an attacker that discovers the LDAP password automatically gains access to your application, and viceversa.
Force the user (that usually wants the same password everywhere because it's easy to remember) to choose a different password by checking its equality (against the LDAP one) when creating a new password in your webapp.
You should not save users passwords anywhere, because anyone with database access would be able to retrieve all the passwords.
The correct way to go is not encryption, but one-way hashing (better with Salt, to prevent Rainbow Tables attacks):
In Java one of the best implementations out there is jBCrypt, based on BCrypt.
Because it's more safe for different reasons Jon Skeet said it :)