public abstract class OncePerRequestFilter extends GenericFilterBean
doFilterInternal(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, javax.servlet.FilterChain)method with HttpServletRequest and HttpServletResponse arguments.
As of Servlet 3.0, a filter may be invoked as part of a
ASYNC dispatches that occur in
separate threads. A filter can be configured in
web.xml whether it
should be involved in async dispatches. However, in some cases servlet
containers assume different default configuration. Therefore sub-classes can
override the method
shouldNotFilterAsyncDispatch() to declare
statically if they should indeed be invoked, once, during both types
of dispatches in order to provide thread initialization, logging, security,
and so on. This mechanism complements and does not replace the need to
configure a filter in
web.xml with dispatcher types.
Subclasses may use
determine when a filter is invoked as part of an async dispatch, and use
isAsyncStarted(HttpServletRequest) to determine when the request
has been placed in async mode and therefore the current dispatch won't be
the last one for the given request.
Yet another dispatch type that also occurs in its own thread is
ERROR. Subclasses can override
shouldNotFilterErrorDispatch() if they wish to declare statically
if they should be invoked once during error dispatches.
getAlreadyFilteredAttributeName() method determines how to
identify that a request is already filtered. The default implementation is
based on the configured name of the concrete filter instance.
|Modifier and Type||Field and Description|
Suffix that gets appended to the filter name for the "already filtered" request attribute.
|Constructor and Description|
|Modifier and Type||Method and Description|
Same contract as for
Typically an ERROR dispatch happens after the REQUEST dispatch completes, and the filter chain starts anew.
Return the name of the request attribute that identifies that a request is already filtered.
The dispatcher type
Whether request processing is in asynchronous mode meaning that the response will not be committed after the current thread is exited.
Can be overridden in subclasses for custom filtering control, returning
The dispatcher type
Whether to filter error dispatches such as when the servlet container processes and error mapped in
addRequiredProperty, afterPropertiesSet, createEnvironment, destroy, getEnvironment, getFilterConfig, getFilterName, getServletContext, init, initBeanWrapper, initFilterBean, setBeanName, setEnvironment, setServletContext
public final void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws ServletException, IOException
doFilterimplementation stores a request attribute for "already filtered", proceeding without filtering again if the attribute is already there.
ServletRequestobject contains the client's request
ServletResponseobject contains the filter's response
FilterChainfor invoking the next filter or the resource
ServletException- if an exception occurs that interferes with the filter's normal operation
IOException- if an I/O related error has occurred during the processing
doFilterInternal(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, javax.servlet.FilterChain)
protected boolean isAsyncDispatch(HttpServletRequest request)
javax.servlet.DispatcherType.ASYNCintroduced in Servlet 3.0 means a filter can be invoked in more than one thread over the course of a single request. This method returns
trueif the filter is currently executing within an asynchronous dispatch.
request- the current request
protected boolean isAsyncStarted(HttpServletRequest request)
request- the current request
protected String getAlreadyFilteredAttributeName()
The default implementation takes the configured name of the concrete filter instance and appends ".FILTERED". If the filter is not fully initialized, it falls back to its class name.
protected boolean shouldNotFilter(HttpServletRequest request) throws ServletException
trueto avoid filtering of the given request.
The default implementation always returns
request- current HTTP request
ServletException- in case of errors
protected boolean shouldNotFilterAsyncDispatch()
javax.servlet.DispatcherType.ASYNCintroduced in Servlet 3.0 means a filter can be invoked in more than one thread over the course of a single request. Some filters only need to filter the initial thread (e.g. request wrapping) while others may need to be invoked at least once in each additional thread for example for setting up thread locals or to perform final processing at the very end.
Note that although a filter can be mapped to handle specific dispatcher
web.xml or in Java through the
servlet containers may enforce different defaults with regards to
dispatcher types. This flag enforces the design intent of the filter.
The default return value is "true", which means the filter will not be invoked during subsequent async dispatches. If "false", the filter will be invoked during async dispatches with the same guarantees of being invoked only once during a request within a single thread.
protected boolean shouldNotFilterErrorDispatch()
web.xml. The default return value is "true", which means the filter will not be invoked in case of an error dispatch.
protected abstract void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException
doFilter, but guaranteed to be just invoked once per request within a single request thread. See
Provides HttpServletRequest and HttpServletResponse arguments instead of the default ServletRequest and ServletResponse ones.
protected void doFilterNestedErrorDispatch(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException
sendErroron the response. In that case we are still in the filter chain, on the same thread, but the request and response have been switched to the original, unwrapped ones.
Sub-classes may use this method to filter such nested ERROR dispatches
and re-apply wrapping on the request or response.
context, if any, should still be active as we are still nested within
the filter chain.