A security role reference defines a mapping between the name of a role that is called from a web component using isUserInRole(String role) and the name of a security role that has been defined for the application. If no <security-role-ref> element is declared in a deployment descriptor, and the isUserInRole method is called, the container defaults to checking the provided role name against the list of all security roles defined for the web application. Using the default method instead of using the security-role-ref element limits your flexibility to change role names in an application without also recompiling the servlet making the call.
The security-role-ref element is used when an application uses the HttpServletRequest.isUserInRole(String role) method. The value passed to the isUserInRole method is a String representing the role name of the user. The value of the role-name element must be the String used as the parameter to the HttpServletRequest.isUserInRole(String role) method. The role-link must contain the name of one of the security roles defined in the security-role elements. The container uses the mapping of security-role-ref to security-role when determining the return value of the call.
For example, to map the security role reference cust to the security role with role name bankCustomer, the syntax would be:
<servlet> ... <security-role-ref> <role-name>cust</role-name> <role-link>bankCustomer</role-link> </security-role-ref> ... </servlet>
In this case, if the servlet called by a user belonging to the bankCustomer security role made the API call, isUserInRole("cust") would return true.
The <role-link> element in the security-role-ref element must match a <role-name> defined in the <security-role> element of the same web.xml deployment descriptor, as shown here:
<security-role> <role-name>bankCustomer</role-name> </security-role>
A security role reference, including the name defined by the reference, is scoped to the component whose deployment descriptor contains the security-role-ref deployment descriptor element.