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

所有已实现的接口:
Filter, Aware, BeanNameAware, DisposableBean, InitializingBean, EnvironmentAware, EnvironmentCapable, 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 (e.g. a View) is still rendered. As such, this filter only saves bandwidth, not server performance.
NOTE: As of Spring Framework 5.0, this filter uses request/response decorators built on the Servlet 3.1 API.
从以下版本开始:
3.0
作者:
Arjen Poutsma, Rossen Stoyanchev, Brian Clozel, Juergen Hoeller

字段概要
- 从类继承的字段 org.springframework.web.filter.OncePerRequestFilter
  ALREADY_FILTERED_SUFFIX
- 从类继承的字段 org.springframework.web.filter.GenericFilterBean
  logger

构造器概要
构造器
构造器说明
ShallowEtagHeaderFilter()

方法概要

所有方法静态方法实例方法具体方法
修饰符和类型	方法	说明
`static void`	`disableContentCaching(ServletRequest request)`	This method can be used to suppress the content caching response wrapper of the ShallowEtagHeaderFilter.
`protected 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`	`generateETagHeaderValue(InputStream inputStream, boolean isWeak)`	Generate the ETag header value from the given response body byte array.
`protected boolean`	`isEligibleForEtag(HttpServletRequest request, HttpServletResponse response, int responseStatusCode, InputStream inputStream)`	Whether an ETag should be calculated for the given request and response exchange.
`boolean`	`isWriteWeakETag()`	Return whether the ETag value written to the response should be weak, as per RFC 7232.
`void`	`setWriteWeakETag(boolean writeWeakETag)`	Set whether the ETag value written to the response should be weak, as per RFC 7232.
`protected boolean`	`shouldNotFilterAsyncDispatch()`	The default value is `false` so that the filter may delay the generation of an ETag until the last asynchronously dispatched thread.

从类继承的方法 org.springframework.web.filter.OncePerRequestFilter
doFilter, doFilterNestedErrorDispatch, getAlreadyFilteredAttributeName, isAsyncDispatch, isAsyncStarted, shouldNotFilter, shouldNotFilterErrorDispatch

从类继承的方法 org.springframework.web.filter.GenericFilterBean
addRequiredProperty, afterPropertiesSet, createEnvironment, destroy, getEnvironment, getFilterConfig, getFilterName, getServletContext, init, initBeanWrapper, initFilterBean, setBeanName, setEnvironment, setServletContext

从类继承的方法 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- 构造器详细资料
  - ShallowEtagHeaderFilter
```
public ShallowEtagHeaderFilter()
```
- 方法详细资料
  - setWriteWeakETag
```
public void setWriteWeakETag(boolean writeWeakETag)
```
    Set whether the ETag value written to the response should be weak, as per RFC 7232.
    Should be configured using an <init-param> for parameter name "writeWeakETag" in the filter definition in web.xml.
    从以下版本开始:
    4.3
    另请参阅:
    RFC 7232 section 2.3
  - isWriteWeakETag
```
public boolean isWriteWeakETag()
```
    Return whether the ETag value written to the response should be weak, as per RFC 7232.
    从以下版本开始:
    4.3
  - shouldNotFilterAsyncDispatch
```
protected boolean shouldNotFilterAsyncDispatch()
```
    The default value is false so that the filter may delay the generation of an ETag until the last asynchronously dispatched thread.
    覆盖:
    shouldNotFilterAsyncDispatch 在类中 OncePerRequestFilter
  - doFilterInternal
```
protected void doFilterInternal(HttpServletRequest request,
                                HttpServletResponse response,
                                FilterChain filterChain)
                         throws ServletException,
                                IOException
```
    从类复制的说明: OncePerRequestFilter
    Same contract as for doFilter, but guaranteed to be just invoked once per request within a single request thread. See OncePerRequestFilter.shouldNotFilterAsyncDispatch() for details.
    Provides HttpServletRequest and HttpServletResponse arguments instead of the default ServletRequest and ServletResponse ones.
    指定者:
    doFilterInternal 在类中 OncePerRequestFilter
    抛出:
    ServletException
    IOException
  - isEligibleForEtag
```
protected boolean isEligibleForEtag(HttpServletRequest request,
                                    HttpServletResponse response,
                                    int responseStatusCode,
                                    InputStream inputStream)
```
    Whether an ETag should be calculated for the given request and response exchange. By default this is true if all of the following match:
    Response is not committed.
    Response status codes is in the 2xx series.
    Request method is a GET.
    Response Cache-Control header does not contain "no-store" (or is not present at all).
    参数:
    request - the HTTP request
    response - the HTTP response
    responseStatusCode - the HTTP response status code
    inputStream - the response body
    返回:
    true if eligible for ETag generation, false otherwise
  - generateETagHeaderValue
```
protected String generateETagHeaderValue(InputStream inputStream,
                                         boolean isWeak)
                                  throws IOException
```
    Generate the ETag header value from the given response body byte array.
    The default implementation generates an MD5 hash.
    参数:
    inputStream - the response body as an InputStream
    isWeak - whether the generated ETag should be weak
    返回:
    the ETag header value
    抛出:
    IOException
    另请参阅:
    DigestUtils
  - disableContentCaching
```
public static void disableContentCaching(ServletRequest request)
```
    This method can be used to suppress the content caching response wrapper of the ShallowEtagHeaderFilter. The main reason for this is streaming scenarios which are not to be cached and do not need an eTag.
    Note: This method must be called before the response is written to in order for the entire response content to be written without caching.
    从以下版本开始:
    4.2

类 ShallowEtagHeaderFilter

字段概要

从类继承的字段 org.springframework.web.filter.OncePerRequestFilter

从类继承的字段 org.springframework.web.filter.GenericFilterBean

构造器概要

方法概要

从类继承的方法 org.springframework.web.filter.OncePerRequestFilter

从类继承的方法 org.springframework.web.filter.GenericFilterBean

从类继承的方法 java.lang.Object

构造器详细资料

ShallowEtagHeaderFilter

方法详细资料

setWriteWeakETag

isWriteWeakETag

shouldNotFilterAsyncDispatch

doFilterInternal

isEligibleForEtag

generateETagHeaderValue

disableContentCaching