使用自定义NSURLProtocol时，UIWebView无法加载重定向页面的内容

Question

我有一个UIWebView和一个自定义的NSURLProtocol类，用于代理HTTP请求。我在加载github.com时遇到问题。如果我浏览到https://github.com，那么它会加载页面及其内容。但是，如果我浏览到http://github.com，它会正确加载HTML，但它不会加载图像或CSS。这是我加载https版本时的样子：

这是我加载http版本时的样子：

这是我用来重现此问题的视图控制器的代码：

@interface ViewController ()
{
    UIWebView *aWebView;
}
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    [NSURLProtocol registerClass:[WebViewProxyURLProtocol class]];

    aWebView = [[UIWebView alloc] initWithFrame:self.view.frame];
    aWebView.delegate = self;
    [self.view addSubview:aWebView];

    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://github.com"]];
    [aWebView loadRequest:request];
}

@end

这是NSURLProtocol的实现：

@interface WebViewProxyURLProtocol : NSURLProtocol <NSURLConnectionDataDelegate>

@end

@implementation WebViewProxyURLProtocol {
    NSMutableURLRequest* correctedRequest;
}

+ (BOOL)canInitWithRequest:(NSURLRequest *)request {
    return ([[request allHTTPHeaderFields] objectForKey:@"X-WebViewProxy"] == nil);
}

+ (NSURLRequest *)canonicalRequestForRequest:(NSURLRequest *)request {
    return request;
}

+ (BOOL)requestIsCacheEquivalent:(NSURLRequest *)a toRequest:(NSURLRequest *)b {
    return NO;
}

- (id)initWithRequest:(NSURLRequest *)request cachedResponse:(NSCachedURLResponse *)cachedResponse client:(id<NSURLProtocolClient>)client {
    if (self = [super initWithRequest:request cachedResponse:cachedResponse client:client]) {
        // Add header to prevent loop in proxy
        correctedRequest = request.mutableCopy;
        [correctedRequest addValue:@"True" forHTTPHeaderField:@"X-WebViewProxy"];
    }
    return self;
}

- (void)startLoading {
    [NSURLConnection connectionWithRequest:correctedRequest delegate:self];
}

- (void)stopLoading {
    correctedRequest = nil;
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
    [self.client URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    [self.client URLProtocol:self didLoadData:data];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
    [self.client URLProtocolDidFinishLoading:self];
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
    [self.client URLProtocol:self didFailWithError:error];
}

- (NSURLRequest *)connection:(NSURLConnection *)connection
             willSendRequest:(NSURLRequest *)request
            redirectResponse:(NSURLResponse *)redirectResponse
{
    return request;
}

- (NSCachedURLResponse *)connection:(NSURLConnection *)connection
                  willCacheResponse:(NSCachedURLResponse *)cachedResponse
{
    return nil;
}

@end

如果我禁用自定义NSURLProtocol类，它可以正常工作。我使用Charles来检查HTTP请求和响应，它们在使用和不使用NSURLProtocol时看起来相同。

所以问题是：为什么UIWebView在使用NSURLConnection获取页面数据时不会请求网页内容？

Answer 1

我们做了同样的工作 - 重定向工作但内容没有加载。

在Apple doc之后，他们提到重定向应该使用NSURLProtocol子类中的连接：willSendRequest：redirectResponse委托方法来处理。

我们的解决方案最终看起来像这样：

- (NSURLRequest *)connection:(NSURLConnection *)connection willSendRequest:(NSURLRequest *)request redirectResponse:(NSURLResponse *)response {
  if (response) {
    NSMutableURLRequest *redirect = [request mutableCopy];
    [NSURLProtocol removePropertyForKey:kFlagRequestHandled inRequest:redirect];
    [RequestHelper addWebViewHeadersToRequest:redirect];

    // THE IMPORTANT PART
    [self.client URLProtocol:self wasRedirectedToRequest:redirect redirectResponse:response];

    return redirect;
  }

return request;

}

Answer 2

我最终想到了这一点。当我在连接中得到重定向响应（HTTP 3xx）时：didReceiveResponse：我不得不调用[self.client URLProtocol：self wasRedirectedToRequest：redirectRequest redirectResponse：response]。

Answer 3

对于那些寻找Swift解决方案的人来说，我已经采用了@micmdk所做的并对其进行了调整。

在我的情况下，我使用URLProtocol类拦截请求。在override func startLoading()方法中，我在请求上设置了一个属性：

override func startLoading() {
    ...
    guard let mutableRequest = request as? NSMutableURLRequest else {
        exit(0)
    }

    URLProtocol.setProperty("true", forKey:"requestHasBeenHandled", in: mutableRequest)

    return mutableRequest as URLRequest
}

这可以防止重定向被处理。所以我删除了属性，如下：

func urlSession(_ session: URLSession, task: URLSessionTask, willPerformHTTPRedirection response: HTTPURLResponse, newRequest request: URLRequest, completionHandler: @escaping (URLRequest?) -> Void) {
    guard let redirect = request as? NSMutableURLRequest else {
        exit(0)
    }

    URLProtocol.removeProperty(forKey: "requestHasBeenHandled", in: redirect)

    self.client?.urlProtocol(self, wasRedirectedTo: redirect as URLRequest, redirectResponse: response)
}

确认它有效。图像和资产正确加载。