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[英]URLResponse cached although response's cache-control header is set to no-cache
[英]Would a file with a response header `Cache-Control:Private` be prevented from being cached in a NSURLCache?
是否可以防止将带有响应标头Cache-Control:Private
的文件缓存在NSURLCache
? 共享缓存(如setSharedCache
和NSURLCache.sharedCache()
)还是自定义缓存?
为了进行扩展,我具有UIWebView
,离线时需要访问它。 此WebView
的源具有与其关联的多个外部CSS和JS文件。 我可以缓存大多数站点(CSS等都放在适当的位置),但是似乎没有缓存提供站点重要信息的特定JavaScript文件。 我注意到不会缓存的文件与其余文件之间的区别是,它的Cache-Control设置为私有(其他是公共的)。 但是,据我了解,将缓存控件设置为私有是为了防止在代理服务器上缓存。 它会影响iOS上的缓存吗?
设置缓存
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
let URLCache: NSURLCache = NSURLCache(memoryCapacity: 10 * 1024 * 1024,
diskCapacity: 50 * 1024 * 1024,
diskPath: nil)
NSURLCache.setSharedURLCache(URLCache)
println("Disk cache usage: \(NSURLCache.sharedURLCache().currentDiskUsage)")
// http://stackoverflow.com/questions/21957378/how-to-cache-using-nsurlsession-and-nsurlcache-not-working
sleep(1)
return true
}
使用缓存
func getWebPage(onCompletion: (NSString, NSURL) -> Void) {
let url = getApplicationSelectorURL()
let request = NSURLRequest(URL: url, cachePolicy: .ReturnCacheDataElseLoad, timeoutInterval: 10.0)
let queue = NSOperationQueue()
NSURLConnection.sendAsynchronousRequest(request, queue: queue, completionHandler: { response, data, error in
println("Web page task completed")
var cachedResponse: NSCachedURLResponse
if (error != nil) {
println("NSURLConnection error: \(error.localizedDescription)")
if let cachedResponse = NSURLCache.sharedURLCache().cachedResponseForRequest(request) {
if let htmlString = NSString(data: cachedResponse.data, encoding: NSUTF8StringEncoding) {
onCompletion(htmlString, url)
} else {
println("htmlString nil")
}
} else {
println("cacheResponse nil")
}
} else {
cachedResponse = NSCachedURLResponse(response: response, data: data, userInfo: nil, storagePolicy: .Allowed)
NSURLCache.sharedURLCache().storeCachedResponse(cachedResponse, forRequest: request)
if let htmlString = NSString(data: data, encoding: NSUTF8StringEncoding) {
onCompletion(htmlString, url)
} else {
println("htmlString nil")
}
}
})
}
填充UIWebView
APICommunicator.sharedInstance.getWebPage({ htmlString, url in
dispatch_async(dispatch_get_main_queue(),{
self.webView.loadHTMLString(htmlString, baseURL: url)
})
})
我最终创建了一个类似于NSURLConnectionDelegate
方法willCacheResponse
的方法,并替换了Cache-Control:private
标头。
willCacheResponse方法
func willCacheResponse(cachedResponse: NSCachedURLResponse) -> NSCachedURLResponse?
{
let response = cachedResponse.response
let HTTPresponse: NSHTTPURLResponse = response as NSHTTPURLResponse
let headers: NSDictionary = HTTPresponse.allHeaderFields
var modifiedHeaders: NSMutableDictionary = headers.mutableCopy() as NSMutableDictionary
modifiedHeaders["Cache-Control"] = "max-age=604800"
let modifiedResponse: NSHTTPURLResponse = NSHTTPURLResponse(
URL: HTTPresponse.URL!,
statusCode: HTTPresponse.statusCode,
HTTPVersion: "HTTP/1.1",
headerFields: modifiedHeaders)!
let modifiedCachedResponse = NSCachedURLResponse(
response: modifiedResponse,
data: cachedResponse.data,
userInfo: cachedResponse.userInfo,
storagePolicy: cachedResponse.storagePolicy)
return modifiedCachedResponse
}
调用方法
if let cachedResponse = self.willCacheResponse(
NSCachedURLResponse(response: response,
data: data,
userInfo: nil,
storagePolicy: .Allowed)) {
NSURLCache.sharedURLCache().storeCachedResponse(cachedResponse, forRequest: request)
}
现在,它在脱机时可以正确显示。 真是一段旅程。
是的, NSURLCache
不会缓存具有专用缓存控制策略的NSURLCache
。 RFC#2616说
私人:指示全部或部分响应消息是针对单个用户的,并且不得由共享缓存缓存。 这允许源服务器声明响应的指定部分仅面向一个用户,而不是针对其他用户的请求的有效响应。 私有(非共享)缓存可以缓存响应。
好吧, NSURLCache
使用了sharedCache ,您甚至可以在发布的代码中进行设置。 我猜它可以解释几乎所有内容。
解决方案是更改服务器行为,或重写NSURLCache
类的某些方法。 (例如,您可以重写客户端头文件,但这确实是一个很糟糕的技巧。)
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