cookie机制采用的是在客户端保持 HTTP 状态信息的方案
Cookie是在浏览器访问WEB服务器的某个资源时,由WEB服务器在HTTP响应消息头中附带传送给浏览器的一个小文本文件。
一旦WEB浏览器保存了某个Cookie,那么它在以后每次访问该WEB服务器时,都会在HTTP请求头中将这个Cookie回传给WEB服务器。
底层的实现原理: WEB服务器通过在HTTP响应消息中增加Set-Cookie响应头字段将Cookie信息发送给浏览器,浏览器则通过在HTTP请求消息中增加Cookie请求头字段将Cookie回传给WEB服务器。
一个Cookie只能标识一种信息,它至少含有一个标识该信息的名称(NAME)和设置值(VALUE)。
一个WEB站点可以给一个WEB浏览器发送多个Cookie,一个WEB浏览器也可以存储多个WEB站点提供的Cookie。
浏览器一般只允许存放300个Cookie,每个站点最多存放20个Cookie,每个Cookie的大小限制为4KB。
开启cookie支持
useCookiePersistence= yes。默认是开启的
如果 useCookiePersistence= yes,在- (void)readResponseHeaders 方法中有这么一段,在Response后创建并存储cookie
// Handle cookies
NSArray *newCookies = [NSHTTPCookie cookiesWithResponseHeaderFields:[self responseHeaders] forURL:[self url]];
[self setResponseCookies:newCookies];
if ([self useCookiePersistence]) {
// Store cookies in global persistent store
[[NSHTTPCookieStorage sharedHTTPCookieStorage] setCookies:newCookies forURL:[self url] mainDocumentURL:nil];
// We also keep any cookies in the sessionCookies array, so that we have a reference to them if we need to remove them later
NSHTTPCookie *cookie;
for (cookie in newCookies) {
[ASIHTTPRequest addSessionCookie:cookie];
}
}
cookie信息被存储在NSHTTPCookieStorage中。
具体cookie相关的方法如下:
+ (NSMutableArray *)sessionCookies
{
if (!sessionCookies) {
[ASIHTTPRequest setSessionCookies:[[[NSMutableArray alloc] init] autorelease]];
}
return sessionCookies;
}
+ (void)setSessionCookies:(NSMutableArray *)newSessionCookies
{
[sessionCookiesLock lock];
// Remove existing cookies from the persistent store
for (NSHTTPCookie *cookie in sessionCookies) {
[[NSHTTPCookieStorage sharedHTTPCookieStorage] deleteCookie:cookie];
}
[sessionCookies release];
sessionCookies = [newSessionCookies retain];
[sessionCookiesLock unlock];
}
+ (void)addSessionCookie:(NSHTTPCookie *)newCookie
{
[sessionCookiesLock lock];
NSHTTPCookie *cookie;
NSUInteger i;
NSUInteger max = [[ASIHTTPRequest sessionCookies] count];
for (i=0; i<max; i++) {
cookie = [[ASIHTTPRequest sessionCookies] objectAtIndex:i];
if ([[cookie domain] isEqualToString:[newCookie domain]] && [[cookie path] isEqualToString:[newCookie path]] && [[cookie name] isEqualToString:[newCookie name]]) {
[[ASIHTTPRequest sessionCookies] removeObjectAtIndex:i];
break;
}
}
[[ASIHTTPRequest sessionCookies] addObject:newCookie];
[sessionCookiesLock unlock];
}
// Dump all session data (authentication and cookies)
+ (void)clearSession
{
[sessionCredentialsLock lock];
[[[self class] sessionCredentialsStore] removeAllObjects];
[sessionCredentialsLock unlock];
[[self class] setSessionCookies:nil];
[[[self class] defaultCache] clearCachedResponsesForStoragePolicy:ASICacheForSessionDurationCacheStoragePolicy];
}
在request head 中添加cookie信息的方法
- (void)applyCookieHeader { // Add cookies from the persistent (mac os global) store if ([self useCookiePersistence]) { NSArray *cookies = [[NSHTTPCookieStorage sharedHTTPCookieStorage] cookiesForURL:[[self url] absoluteURL]]; if (cookies) { [[self requestCookies] addObjectsFromArray:cookies]; } } // Apply request cookies NSArray *cookies; if ([self mainRequest]) { cookies = [[self mainRequest] requestCookies]; } else { cookies = [self requestCookies]; } if ([cookies count] > 0) { NSHTTPCookie *cookie; NSString *cookieHeader = nil; for (cookie in cookies) { if (!cookieHeader) { cookieHeader = [NSString stringWithFormat: @"%@=%@",[cookie name],[cookie value]]; } else { cookieHeader = [NSString stringWithFormat: @"%@; %@=%@",cookieHeader,[cookie name],[cookie value]]; } } if (cookieHeader) { [self addRequestHeader:@"Cookie" value:cookieHeader]; } } }
这里的cookie为什么是个NSArray呢???难道会有多个cookie