In general, security management should be enforced by the container in a manner that is transparent to the web component. The security API described in this section should be used only in the less frequent situations in which the web component methods need to access the security context information.
Servlet 3.0 specifies the following methods of the HttpServletRequest interface that enable you to verify a caller's identity programmatically, and to use that information to grant or deny access to data:
The HttpServletRequest interface provides the following methods that enable you to access security information about the component’s caller:getRemoteUser: Determines the user name with which the client authenticated. The getRemoteUser method returns the name of the remote user (that is, the caller) associated by the container with the request. If no user has been authenticated, this method returns null.
The <security-role-ref> element should be declared in the deployment descriptor with a <role-name> sub-element containing the role name to be passed to the method. Using security role references is discussed in Declaring and Linking Role References.
getUserPrincipal: Determines the principal name of the current user and returns a java.security.Principal object. If no user has been authenticated, this method returns null. Calling the getName method on the Principal returned by getUserPrincipal returns the name of the remote user.
Your application can make business logic decisions based on the information obtained using these APIs.