public void setUsernameParam(String usernameParam) {
        this.usernameParam = usernameParam;
    }
Sets the request parameter name to look for when acquiring the username.  Unless overridden by calling this
method, the default is <code>username</code>.

@param usernameParam the name of the request param to check for acquiring the username.
web/src/main/java/org/apache/shiro/web/filter/authc/FormAuthenticationFilter.java