public void setLoginUrl(String loginUrl) {
        this.loginUrl = loginUrl;
    }
Sets the application's login URL to be assigned to all acquired Filters that subclass
{@link AccessControlFilter}.  This is a convenience mechanism: for all configured {@link #setFilters filters},
as well for any default ones ({@code authc}, {@code user}, etc.), this value will be passed on to each Filter
via the {@link AccessControlFilter#setLoginUrl(String)} method<b>*</b>.  This eliminates the need to
configure the 'loginUrl' property manually on each filter instance, and instead that can be configured once
via this attribute.
<p/>
<b>*</b>If a filter already has already been explicitly configured with a value, it will
<em>not</em> receive this value. Individual filter configuration overrides this global convenience property.

@param loginUrl the application's login URL to apply to as a convenience to all discovered
                {@link AccessControlFilter} instances.
@see AccessControlFilter#setLoginUrl(String)
support/spring/src/main/java/org/apache/shiro/spring/web/ShiroFilterFactoryBean.java