java.lang.Object
- org.springframework.web.filter.GenericFilterBean
- - org.springframework.web.filter.OncePerRequestFilter

All Implemented Interfaces:
Filter, Aware, BeanNameAware, DisposableBean, InitializingBean, EnvironmentAware, EnvironmentCapable, ServletContextAware
Direct Known Subclasses:
AbstractRequestLoggingFilter, CharacterEncodingFilter, CorsFilter, ForwardedHeaderFilter, HiddenHttpMethodFilter, HttpPutFormContentFilter, MultipartFilter, OpenEntityManagerInViewFilter, OpenPersistenceManagerInViewFilter, OpenSessionInViewFilter, OpenSessionInViewFilter, OpenSessionInViewFilter, RelativeRedirectFilter, RequestContextFilter, 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 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 Description
OncePerRequestFilter()

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	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, createEnvironment, destroy, getEnvironment, 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

Class OncePerRequestFilter

Field Summary

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

Constructor Summary

Method Summary

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

Methods inherited from class java.lang.Object

Field Detail

ALREADY_FILTERED_SUFFIX

Constructor Detail

OncePerRequestFilter

Method Detail

doFilter

isAsyncDispatch

isAsyncStarted

getAlreadyFilteredAttributeName

shouldNotFilter

shouldNotFilterAsyncDispatch

shouldNotFilterErrorDispatch

doFilterInternal