INCLUDE: Use this for the filter to be applied to any include targets matching a specified servlet name or with URLs matching a specified pattern.
FORWARD: Use this for the filter to be applied to any forward targets matching a specified servlet name or with URLs matching a specified pattern.
REQUEST: Use this in addition to an INCLUDE or FORWARD setting (one <dispatcher> element for each setting) for the filter to also be applied to direct request targets matching a specified servlet name or with URLs matching a specified pattern. (It is nonsensical to use the REQUEST value only. If you want the filter to apply only to direct requests, there is no need to use the <dispatcher> element.)
ERROR: Use this for the filter to be applied under the error page mechanism.
