The cookie contains three part:

username: to identify logged-in 

expirationTime: to expire the cookie; default 2 week

password and pridefined : encode by md5 hash.

Notice when use standard Remember Me solution: 

1) cookie depend on user and password so we change user or password then cookie is invalid

2)  potentially vulnerable if the remember me cookie is captured.

Use: 

Type 1:  standard Remember Me solution

Type 2: Using PersistentTokenBasedRememberMeServices via an implementation JdbcTokenRepositoryImpl store the persisted login information in a database