javax.portlet.filter

Interface HeaderFilter

All Superinterfaces:

PortletFilter

public interface HeaderFilter
extends PortletFilter

The HeaderFilter is an object that performs filtering tasks on either the header request to a portlet, or on the header response from a portlet, or both.

Filters perform filtering in the doFilter method. Every Filter has access to a FilterConfig object from which it can obtain its initialization parameters, a reference to the PortletContext which it can use, for example, to load resources needed for filtering tasks.

Filters are configured in the portlet deployment descriptor of a portlet application.

Since:

3.0

Method Summary

Modifier and Type	Method and Description
void	doFilter(HeaderRequest request, HeaderResponse response, HeaderFilterChain chain) The doFilter method of the Filter is called by the portlet container each time a header request/response pair is passed through the chain due to a client request for a portlet method at the end of the chain.

Methods inherited from interface javax.portlet.filter.PortletFilter

destroy, init

Method Detail

doFilter

void doFilter(HeaderRequest request,
              HeaderResponse response,
              HeaderFilterChain chain)
       throws IOException,
              PortletException

The doFilter method of the Filter is called by the portlet container each time a header request/response pair is passed through the chain due to a client request for a portlet method at the end of the chain.

The FilterChain passed in to this method allows the Filter to pass on the header request and response to the next component in the chain.

The doFilter method of a filter will typically be implemented following this or some subset of the following pattern:

• The method examines the request information.
• The method may wrap the request object passed in to its doFilter method with a customized implementation the request wrapper HeaderRequestWrapper in order to modify request data.
• The method may wrap the response object passed in to its doFilter method with a customized implementation of the response wrapper HeaderResponseWrapper to modify response data.
• The filter may invoke the next component in the filter chain. The next component may be another filter, or if the filter making the invocation is the last filter configured in the deployment descriptor for this chain, the next component is the target method of the portlet. The invocation of the next component is effected by calling the doFilter method on the FilterChain object, and passing in the request and response with which it was called or passing in wrapped versions it may have created. The filter chain's implementation of the doFilter method, provided by the portlet container, must locate the next component in the filter chain and invoke its doFilter method, passing in the appropriate request and response objects. Alternatively, the filter chain can block the request by not making the call to invoke the next component, leaving the filter responsible for filling out the response object.
• After invocation of the next filter in the chain, the filter may examine the response data.
• Alternatively, the filter may have thrown an exception to indicate an error in processing. If the filter throws an UnavailableException during its doFilter processing, the portlet container must not attempt continued processing down the filter chain. It may choose to retry the whole chain at a later time if the exception is not marked permanent.
• When the last filter in the chain has been invoked, the next component accessed is the target method on the portlet at the end of the chain.

Parameters:

request - the current header request

response - the current header response

chain - the remaining filter chain

Throws:

IOException - if an IO error occurred in the filter processing

PortletException - if a portlet exception occurred in the filter processing