cache-control

Any valid HTTP headers can be put in these files. This provides another way to apply the Expires header, and it's a way to add the Cache-Control headers. The relevant Cache-Control headers are:
Cache-Control : max-age = [delta-seconds]
    Modifies the expiration mechanism, overriding the Expires header. Max-age implies Cache-Control : public.
Cache-Control : public
    Indicates that the object may be stored in a cache. This is the default.
Cache-Control : private
Cache-Control : private = [field-name]
    Indicates that the object (or specified field) must not be stored in a shared cache and is intended for a single user. It may be stored in a private cache.
Cache-Control : no-cache
Cache-Control : no-cache = [field-name]
    Indicates that the object (or specified field) may be cached, but may not be served to a client unless revalidated with the origin server.
Cache-Control : no-store
    Indicates that the item must not be stored in nonvolatile storage, and should be removed as soon as possible from volatile storage.
Cache-Control : no-transform
    Proxies may convert data from one storage system to another. This directive indicates that (most of) the response must not be transformed. (The RFC allows for transformation of some fields, even with this header present.)
Cache-Control : must-revalidate
Cache-Control : proxy-revalidate
    Forces the proxy to revalidate the page even if the client will accept a stale response. Read the RFC before using these headers, there are restrictions on their use.
Caveats and gotchas
    *
      HTTP/1.0 has minimal cache control and only understands the Pragma: no-cache header. Caches using HTTP/1.0 will ignore the Expires and Cache-Control headers.
    *
      None of the Cache-Control directives ensure privacy or security of data. The directives "private" and "no-store" assist in privacy and security, but they are not intended to substitute for authentication and encryption.
    *
      This article is not a substitute for the RFC. If your are implementing the Cache-Control headers, do read the RFC for a detailed description of what each header means and what the limits are.

在jsp页面中
<%
	String path = request.getContextPath();
	HashMap> discounts = DiscountManager.getInnerDiscount();
	response.setHeader("Cache-Control","public,max-age=600");
	response.setDateHeader("Expires",(new Date()).getTime() + 1000 * 60 * 10);
 %>
在HtML代码中
    
    
    
    
  servlet
  response.setHeader("Pragma","No-cache");  
  response.setDateHeader("Expires",0);  
  response.setHeader("Cache-Control","no-cache");   

.Cache-Control头域
　　Cache-Control指定请求和响应遵循的缓存机制。在请求消息或响应消息中设置Cache-Control并不会修改另一个消息处理过程中的缓存处理过程。请求时的缓存指令包括no-cache、no-store、max-age、max-stale、min-fresh、only-if- cached，响应消息中的指令包括public、private、no-cache、no-store、no-transform、must- revalidate、proxy-revalidate、max-age。各个消息中的指令含义如下：
　　Public指示响应可被任何缓存区缓存。
　　Private指示对于单个用户的整个或部分响应消息，不能被共享缓存处理。这允许服务器仅仅描述当用户的部分响应消息，此响应消息对于其他用户的请求无效。
　　no-cache指示请求或响应消息不能缓存
　　no-store用于防止重要的信息被无意的发布。在请求消息中发送将使得请求和响应消息都不使用缓存。
　　max-age指示客户机可以接收生存期不大于指定时间（以秒为单位）的响应。
　　min-fresh指示客户机可以接收响应时间小于当前时间加上指定时间的响应。
　　max-stale指示客户机可以接收超出超时期间的响应消息。如果指定max-stale消息的值，那么客户机可以接收超出超时期指定值之内的响应消息。

评论

1 楼 hnzhangshi 2009-07-14  

学习中，一般在应用中应该用private 会比较好一些吧！