问题描述
是否可能强制浏览器更新缓存的CSS？
Is it possible force the browser to fresh the cached CSS?
这并不像每个请求一样简单。我们有一个网站有一段时间稳定的CSS。
This is not as simple as every request. We have a site that has had stable CSS for a while.
现在我们需要对CSS进行一些主要的更新;但是，缓存CSS的浏览器将不会收到新的CSS几天导致渲染问题。
Now we need to make some major updates to the CSS; however, browsers that have cached the CSS will not receive the new CSS for a couple of days causing rendering issues.
是否有强制刷新CSS的方法，或者我们最好只选择特定于CSS的网址？
Is there a way to force refresh of the CSS or are we better just opting for version specific CSS URLs?
推荐答案
有几个事情要考虑和各种方法来处理。首先，
There are several things to consider and a variety of ways to approach this. First, the spec
理想情况下，修改的资源将在第一次被请求时被无条件地获取，
Ideally, a modified resource will be unconditionally fetched the first time it is requested, and then retrieved from a local cache until it expires with no subsequent server interaction.
保持跟踪不同的排列可能有点混乱，所以我创建了下表。这些观察结果是通过从Chrome向IIS发出请求并在开发者控制台中观察响应/行为而生成的。
Keeping track of the different permutations can be a bit confusing, so I created the following table. These observations were generated by making requests from Chrome against IIS and observing the response/behavior in the developer console.
在所有情况下，新的URL将导致HTTP 200。重要的是使用后续请求会发生什么。
In all cases, a new URL will result in HTTP 200. The important thing is what happens with subsequent requests.
+---------------------+--------------------+-------------------------+
| Type | Cache Headers | Observed Result |
+---------------------+--------------------+-------------------------+
| Static filename | Expiration +1 Year | Taken from cache |
| Static filename | Expire immediately | Never caches |
| Static filename | None | HTTP 304 (not modified) |
| | | |
| Static query string | Expiration +1 Year | HTTP 304 (not modified) |
| Static query string | Expire immediately | HTTP 304 (not modified) |
| Static query string | None | HTTP 304 (not modified) |
| | | |
| Random query string | Expiration +1 Year | Never caches |
| Random query string | Expire immediately | Never caches |
| Random query string | None | Never caches |
+---------------------+--------------------+-------------------------+
不过，请记住，浏览器和网络服务器并不总是符合我们的预期。着名示例：。开发人员不满意。
However, remember that browsers and web servers don't always behave the way we expect. A famous example: in 2012 mobile Safari began caching POST requests. Developers weren't pleased.
随机参数到包含在HTML中的CSS URL的末尾将强制一个新的请求，服务器应该响应HTTP 200（不是304，即使它没有被
修改）。
Appending a random parameter to the end of the CSS URL included in your HTML will force a new request and the server should respond with HTTP 200 (not 304, even if it is hasn't beenmodified).
<link href="normalfile.css?random=@Environment.TickCount" />
当然，如果我们用每个请求随机化查询字符串，将完全失去缓存。
Of course, if we randomize the query string with every request, this will defeat caching entirely. This is rarely/never desirable for a production application.
如果您只维护几个网址，则可以手动修改这些网址，以包含内部版本号或日期：
If you are only maintaining a few URLs, you might manually modify them to contain a build number or a date:
@{
var assembly = Assembly.GetEntryAssembly();
var name = assembly.GetName();
var version = name.Version;
}
<link href="normalfile.css?build=@version.MinorRevision" />
这将在用户代理第一次遇到URL时产生新的请求，返回304s。
This will cause a new request the first time the user agent encounters the URL, but subsequent requests will mostly return 304s. This still causes a request to be made, but at least the whole file isn't served.
一个更好的解决方案是创建一个新的路径。这个过程可以自动用一个版本号（或其他一致的标识符）重写路径。
A better solution is to create a new path. With a little effort, this process can be automated to rewrite the path with a version number (or some other consistent identifier).
显示了一些简单而优雅的选项
This answer shows a few simple and elegant options for non-Microsoft platforms.
Microsoft开发人员可以使用HTTP模块拦截给定文件类型的所有请求，或者可能利用MVC路由/控制器组合提供正确的文件（我没有看到这样做，但我相信这是可行的）。
Microsoft developers can use a HTTP module which intercepts all requests for a given file type(s), or possibly leverage an MVC route/controller combo to serve up the correct file (I haven't seen this done, but I believe it is feasible).
当然，最简单的（不一定是最快的最好的）方法是仅仅重命名每个版本的相关文件，并引用链接标签中的更新路径。
Of course, the simplest (not necessarily the quickest or the best) method is to just rename the files in question with each release and reference the updated paths in the link tags.
- 更改文件名或查询字符串
- 使用仅发生一次的更改
- 文件重命名优于查询字符串更改
- 始终设置HTTP标头以最大化缓存的好处
- Change the file name or query string
- Use a change that only occurs once per release
- File renaming is preferable to a query string change
- Always set HTTP headers to maximize the benefits of caching
这篇关于强制刷新缓存的CSS数据的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！