iOS 关于网络重定向的实现以及相关坑的记录

iOS 关于网络重定向的实现以及相关坑的记录

之前在项目中遇到个问题，既可以说是坑也可以说是自己对一些非常iOS特性的东西的不了解所导致。记录以备有需要的同学或者自己忘了可以回头看看。

先说下简化后的场景：现在server1提供了一个url让我去打开它，然后用户就在这个html的网页上做操作，然后比如点击某个按键提交一些信息到server1，问题来了，这个时候server1与另一个server2做交互并对url进行多次重定向。。具体更复杂一点，大概就是原来用某个url显示的webview经过url的重定向，而我需要拿到每次重定向的response，这里就出现了最后一个response我拿不到的情形。当然每次的request我可以拿到，那么request的url我也可以拿到，那我手动去请求，但这又不符合应用场景，而且也不太科学。

开始折腾了好一会，也很郁闷，后来发现类似这种情况是必须自己手动去实现NSURLProtocol:

@interface RedirectURLProtocol : NSURLProtocol
{
}
@end

#import "RedirectURLProtocol.h"
static NSString * const URLProtocolHandledKey = @"URLProtocolHandledKey";

@interface RedirectURLProtocol ()<NSURLConnectionDelegate>

@property (nonatomic, strong) NSURLConnection *connection;

@end

@implementation RedirectURLProtocol

+ (BOOL)canInitWithRequest:(NSURLRequest *)request
{
    //只处理http和https请求
    NSString *scheme = [[request URL] scheme];
    if ( ([scheme caseInsensitiveCompare:@"http"] == NSOrderedSame ||
          [scheme caseInsensitiveCompare:@"https"] == NSOrderedSame))
    {
        //看看是否已经处理过了，防止无限循环
        if ([NSURLProtocol propertyForKey:URLProtocolHandledKey inRequest:request]) {
            return NO;
        }
        
        return YES;
    }
    return NO;
}

+ (NSURLRequest *)canonicalRequestForRequest:(NSURLRequest *)request {
    NSMutableURLRequest *mutableReqeust = [request mutableCopy];
    mutableReqeust = [self redirectHostInRequset:mutableReqeust];
    return mutableReqeust;
}

+ (BOOL)requestIsCacheEquivalent:(NSURLRequest *)a toRequest:(NSURLRequest *)b
{
    return [super requestIsCacheEquivalent:a toRequest:b];
}

- (void)startLoading
{
    NSMutableURLRequest *mutableReqeust = [[self request] mutableCopy];
    
    //打标签，防止无限循环
    [NSURLProtocol setProperty:@YES forKey:URLProtocolHandledKey inRequest:mutableReqeust];
    
    self.connection = [NSURLConnection connectionWithRequest:mutableReqeust delegate:self];
}

- (void)stopLoading
{
    [self.connection cancel];
}

#pragma mark - NSURLConnectionDelegate
- (void) connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
    [self.client URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
    
    NSHTTPURLResponse* tempResponse = (NSHTTPURLResponse*)response;
    NSLog(@"============ header = %@", tempResponse.allHeaderFields.allKeys);
    
    
}

- (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];
}

#pragma mark -- private
+(NSMutableURLRequest*)redirectHostInRequset:(NSMutableURLRequest*)request
{
    if ([request.URL host].length == 0) {
        return request;
    }
    
    NSString *originUrlString = [request.URL absoluteString];
    NSString *originHostString = [request.URL host];
    NSRange hostRange = [originUrlString rangeOfString:originHostString];
    if (hostRange.location == NSNotFound) {
        return request;
    }
        
    // 替换url，现有不需要去重定向不同的url，所以直接将request的urlcopy
    NSString *urlString = request.URL.absoluteString;
    NSURL *url = [NSURL URLWithString:urlString];
    request.URL = url;
    
    return request;
}
@end

这样子我就将会在- (void) connection:(NSURLConnection )connection didReceiveResponse:(NSURLResponse )response这个函数里获得response
在你需要之前加入以下这句话

[NSURLProtocol registerClass:[RedirectURLProtocol class]];

用完记得还是把它移除掉，不然你的重定向协议是会一直影响你的App的，直到你自己手动移除掉它。

[NSURLProtocol unregisterClass:[RedirectURLProtocol class]];

先记录到这，其实这样子你就可以自己去定制协议定制规则，but最好别这么干吧，需要点功底的感觉。不然自己坑自己的节奏~