How to exclude one url from authorization

Omit the <auth-constraint> element in <security-constraint> for resources for which you don’t need authentication like:

<security-constraint>
    <web-resource-collection>
        <web-resource-name>app</web-resource-name>
        <url-pattern>/info</url-pattern>
    </web-resource-collection>
    <!-- OMIT auth-constraint -->
</security-constraint>

<security-constraint>
    <web-resource-collection>
        <web-resource-name>app</web-resource-name>
        <url-pattern>/*</url-pattern>
    </web-resource-collection>
    <auth-constraint>
        <role-name>Role</role-name>
    </auth-constraint>
</security-constraint>