[[servlet-authentication-unpwd-storage]]
= Storage Mechanisms
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Each of the supported mechanisms for reading a username and password can use any of the supported storage mechanisms:

* Simple Storage with xref:servlet/authentication/passwords/in-memory.adoc#servlet-authentication-inmemory[In-Memory Authentication]
* Relational Databases with xref:servlet/authentication/passwords/jdbc.adoc#servlet-authentication-jdbc[JDBC Authentication]
* Custom data stores with xref:servlet/authentication/passwords/user-details-service.adoc#servlet-authentication-userdetailsservice[UserDetailsService]
* LDAP storage with xref:servlet/authentication/passwords/ldap.adoc#servlet-authentication-ldap[LDAP Authentication]

