org.springframework.web.filter

Class OncePerRequestFilter

java.lang.Object

org.springframework.web.filter.GenericFilterBean

org.springframework.web.filter.OncePerRequestFilter

All Implemented Interfaces:

Filter, Aware, BeanNameAware, DisposableBean, InitializingBean, EnvironmentAware, ServletContextAware

Direct Known Subclasses:

AbstractRequestLoggingFilter, CharacterEncodingFilter, HiddenHttpMethodFilter, HttpPutFormContentFilter, MultipartFilter, OpenEntityManagerInViewFilter, OpenPersistenceManagerInViewFilter, OpenSessionInViewFilter, OpenSessionInViewFilter, RequestContextFilter, ResourceUrlEncodingFilter, ShallowEtagHeaderFilter

public abstract class OncePerRequestFilter
extends GenericFilterBean

Filter base class that aims to guarantee a single execution per request dispatch, on any servlet container. It provides a 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 REQUEST or 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 isAsyncDispatch(HttpServletRequest) to 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.

The 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.

Since:

06.12.2003

Author:

Juergen Hoeller, Rossen Stoyanchev

Field Summary

Fields

Modifier and Type	Field and Description
static String	ALREADY_FILTERED_SUFFIX Suffix that gets appended to the filter name for the "already filtered" request attribute.

Fields inherited from class org.springframework.web.filter.GenericFilterBean

logger

Constructor Summary

Constructors

Constructor and Description
OncePerRequestFilter()

Method Summary

Modifier and Type	Method and Description
void	doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) This doFilter implementation stores a request attribute for "already filtered", proceeding without filtering again if the attribute is already there.
protected abstract void	doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) Same contract as for doFilter, but guaranteed to be just invoked once per request within a single request thread.
protected String	getAlreadyFilteredAttributeName() Return the name of the request attribute that identifies that a request is already filtered.
protected boolean	isAsyncDispatch(HttpServletRequest request) The dispatcher type javax.servlet.DispatcherType.ASYNC introduced in Servlet 3.0 means a filter can be invoked in more than one thread over the course of a single request.
protected boolean	isAsyncStarted(HttpServletRequest request) Whether request processing is in asynchronous mode meaning that the response will not be committed after the current thread is exited.
protected boolean	shouldNotFilter(HttpServletRequest request) Can be overridden in subclasses for custom filtering control, returning true to avoid filtering of the given request.
protected boolean	shouldNotFilterAsyncDispatch() The dispatcher type javax.servlet.DispatcherType.ASYNC introduced in Servlet 3.0 means a filter can be invoked in more than one thread over the course of a single request.
protected boolean	shouldNotFilterErrorDispatch() Whether to filter error dispatches such as when the servlet container processes and error mapped in web.xml.

Methods inherited from class org.springframework.web.filter.GenericFilterBean

addRequiredProperty, afterPropertiesSet, destroy, getFilterConfig, getFilterName, getServletContext, init, initBeanWrapper, initFilterBean, setBeanName, setEnvironment, setServletContext

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ALREADY_FILTERED_SUFFIX

public static final String ALREADY_FILTERED_SUFFIX

Suffix that gets appended to the filter name for the "already filtered" request attribute.

See Also:

getAlreadyFilteredAttributeName(), Constant Field Values

Constructor Detail

OncePerRequestFilter

public OncePerRequestFilter()

Method Detail

doFilter

public final void doFilter(ServletRequest request,
                           ServletResponse response,
                           FilterChain filterChain)
                    throws ServletException,
                           IOException

This doFilter implementation stores a request attribute for "already filtered", proceeding without filtering again if the attribute is already there.

Throws:

ServletException

IOException

See Also:

getAlreadyFilteredAttributeName(), shouldNotFilter(javax.servlet.http.HttpServletRequest), doFilterInternal(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, javax.servlet.FilterChain)

isAsyncDispatch

protected boolean isAsyncDispatch(HttpServletRequest request)

The dispatcher type javax.servlet.DispatcherType.ASYNC introduced 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 true if the filter is currently executing within an asynchronous dispatch.

Parameters:

request - the current request

Since:

3.2

See Also:

WebAsyncManager.hasConcurrentResult()

isAsyncStarted

protected boolean isAsyncStarted(HttpServletRequest request)

Whether request processing is in asynchronous mode meaning that the response will not be committed after the current thread is exited.

Parameters:

request - the current request

Since:

3.2

See Also:

WebAsyncManager.isConcurrentHandlingStarted()

getAlreadyFilteredAttributeName

protected String getAlreadyFilteredAttributeName()

Return the name of the request attribute that identifies that a request is already filtered.

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.

See Also:

GenericFilterBean.getFilterName(), ALREADY_FILTERED_SUFFIX

shouldNotFilter

protected boolean shouldNotFilter(HttpServletRequest request)
                           throws ServletException

Can be overridden in subclasses for custom filtering control, returning true to avoid filtering of the given request.

The default implementation always returns false.

Parameters:

request - current HTTP request

Returns:

whether the given request should not be filtered

Throws:

ServletException - in case of errors

shouldNotFilterAsyncDispatch

protected boolean shouldNotFilterAsyncDispatch()

The dispatcher type javax.servlet.DispatcherType.ASYNC introduced 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 types via web.xml or in Java through the ServletContext, 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.

Since:

3.2

shouldNotFilterErrorDispatch

protected boolean shouldNotFilterErrorDispatch()

Whether to filter error dispatches such as when the servlet container processes and error mapped in web.xml. The default return value is "true", which means the filter will not be invoked in case of an error dispatch.

Since:

3.2

doFilterInternal

protected abstract void doFilterInternal(HttpServletRequest request,
                                         HttpServletResponse response,
                                         FilterChain filterChain)
                                  throws ServletException,
                                         IOException

Same contract as for doFilter, but guaranteed to be just invoked once per request within a single request thread. See shouldNotFilterAsyncDispatch() for details.

Provides HttpServletRequest and HttpServletResponse arguments instead of the default ServletRequest and ServletResponse ones.

Throws:

ServletException

IOException