javax.portlet.filter

Interface ResourceFilter

All Superinterfaces:

PortletFilter

public interface ResourceFilter
extends PortletFilter

The ResourceFilter is an object that performs filtering tasks on either the resource request to a portlet, or on the resource 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.

Asynchronous Processing Considerations

If the ResourceFilter is to support asynchronous mode, care must be taken regarding resource allocation and release. Any resources attached to the ResourceRequest during the inbound portion of the doFilter invocation and needed during asynchronous processing should not be released during outbound processing if asynchronous mode has been started.

If resources must be allocated in this way during inbound processing, the portlet should use a PortletAsyncListener to release the resources upon request completion even when error conditions or timeouts occur.

Alternatively, the portlet may use the AsyncContext#dispatch() method at the end of asynchronous processing in order to cause the portlet resource method to be invoked again with the same ResourceRequest and ResourceResponse objects. The resources can be released during asynchronous dispatch outbound processing if asynchronous mode is not active.

The ResourceRequest#isAsyncStarted() method will return true if the portlet is currently in asynchronous mode. The ResourceRequest#igetDispatcherType() method will return DispatcherType#REQUEST during initial request processing and DipatcherType#ASYNC during processing resulting from an asynchronous dispatch.

Since:

2.0

Method Summary

Modifier and Type	Method and Description
void	doFilter(ResourceRequest request, ResourceResponse response, FilterChain chain) The doFilter method of the Filter is called by the portlet container each time a resource 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(ResourceRequest request,
              ResourceResponse response,
              FilterChain chain)
       throws IOException,
              PortletException

The doFilter method of the Filter is called by the portlet container each time a resource 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 resource 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 ResourceRequestWrapper 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 ResourceResponseWrapper 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 resource request

response - the current resource 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