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:

javax.servlet.Filter, BeanNameAware, DisposableBean, InitializingBean, ServletContextAware

public class ShallowEtagHeaderFilter
extends OncePerRequestFilter

Servlet 2.3/2.4 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 resonse content is not sent, but rather a 304 "Not Modified" status.

Since the ETag is based on the response content, the response (or View) is still rendered. As such, this filter only saves bandwith, not 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(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response, javax.servlet.FilterChain filterChain) Same contract as for doFilter, but guaranteed to be just invoked once per request.
protected java.lang.String	generateETagHeaderValue(byte[] bytes) Generates the ETag header value from the given response body bytes array.

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, 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(javax.servlet.http.HttpServletRequest request,
                                javax.servlet.http.HttpServletResponse response,
                                javax.servlet.FilterChain filterChain)
                         throws javax.servlet.ServletException,
                                java.io.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:

javax.servlet.ServletException

java.io.IOException

generateETagHeaderValue

protected java.lang.String generateETagHeaderValue(byte[] bytes)

Generates the ETag header value from the given response body bytes array.

Default implementation generates an MD5 hash.

Parameters:

bytes - the

Returns:

the ETag header value

See Also:

Md5HashUtils