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## org.springframework.web.filter
Class OncePerRequestFilter

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

All Implemented Interfaces:
  Filter, BeanNameAware, DisposableBean, InitializingBean, ServletContextAware

Direct Known Subclasses:
  AbstractRequestLoggingFilter, CharacterEncodingFilter, HiddenHttpMethodFilter, MultipartFilter, OpenEntityManagerInViewFilter, OpenPersistenceManagerInViewFilter, OpenSessionInViewFilter, RequestContextFilter, ShallowEtagHeaderFilter

    public abstract class OncePerRequestFilter

extends GenericFilterBean

Filter base class that guarantees to be just executed once per request, 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.

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

Field Summary
`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
`OncePerRequestFilter()`

Method Summary
`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.
`protected String` | `getAlreadyFilteredAttributeName()` Return the name of the request attribute that identifies that a request is already filtered.
`protected boolean` | `shouldNotFilter(HttpServletRequest request)` Can be overridden in subclasses for custom filtering control, returning `true` to avoid filtering of the given request.

Methods inherited from class org.springframework.web.filter.GenericFilterBean
`addRequiredProperty, afterPropertiesSet, destroy, getFilterConfig, getFilterName, getServletContext, init, initBeanWrapper, initFilterBean, setBeanName, 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)`

### getAlreadyFilteredAttributeName

    protected String getAlreadyFilteredAttributeName()

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

  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

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

  Throws:
    `ServletException`
    `IOException`

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