org.springframework.web.filter
Class ShallowEtagHeaderFilter

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

All Implemented Interfaces:

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

public class ShallowEtagHeaderFilter
extends OncePerRequestFilter

Filter that generates an ETag value based on the content on the response. This ETag is compared to the If-None-Match header of the request. If these headers are equal, the response content is not sent, but rather a 304 "Not Modified" status instead.

Since the ETag is based on the response content, the response (or View) is still rendered. As such, this filter only saves bandwidth, not server performance.

Since:

3.0

Author:

Arjen Poutsma

Field Summary

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

ALREADY_FILTERED_SUFFIX

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

logger

Constructor Summary

ShallowEtagHeaderFilter()

Method Summary

protected void	doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) Same contract as for doFilter, but guaranteed to be just invoked once per request.
protected String	generateETagHeaderValue(byte[] bytes) Generate the ETag header value from the given response body byte array.
protected boolean	isEligibleForEtag(HttpServletRequest request, HttpServletResponse response, int responseStatusCode, byte[] responseBody) Indicates whether the given request and response are eligible for ETag generation.

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

doFilter, getAlreadyFilteredAttributeName, shouldNotFilter

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

Constructor Detail

ShallowEtagHeaderFilter

public ShallowEtagHeaderFilter()

Method Detail

doFilterInternal

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

Description copied from class: OncePerRequestFilter

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.

Specified by:

doFilterInternal in class OncePerRequestFilter

Throws:

ServletException

IOException

isEligibleForEtag

protected boolean isEligibleForEtag(HttpServletRequest request,
                                    HttpServletResponse response,
                                    int responseStatusCode,
                                    byte[] responseBody)

Indicates whether the given request and response are eligible for ETag generation.

The default implementation returns true for response status codes in the 2xx series.

Parameters:

request - the HTTP request

response - the HTTP response

responseStatusCode - the HTTP response status code

responseBody - the response body

Returns:

true if eligible for ETag generation; false otherwise

generateETagHeaderValue

protected String generateETagHeaderValue(byte[] bytes)

Generate the ETag header value from the given response body byte array.

The default implementation generates an MD5 hash.

Parameters:

bytes - the response body as byte array

Returns:

the ETag header value

See Also:

DigestUtils