iOS端网络拦截技术
NSURLProtocol
NSURLProtocol是URL Loading System的重要组成部分,能够拦截拦截所有基于URL Loading System的网络请求。
URL-Loading-sys.png
可以拦截的网络请求包括NSURLSession，NSURLConnection以及UIWebVIew。
基于CFNetwork的网络请求，以及WKWebView的请求是无法拦截的。
代码不够完善Demo地址--https://github.com/softwarefaith/JiOSDNS
如何使用NSURLProtocol
NSURLProtocol是一个抽象类。创建他的一个子类:
@interface AppDNSInterceptor : NSURLProtocol
分为五个步骤:
注册 -> 拦截 -> 转发 -> 回调 -> 完结
1.注册
对于基于NSURLConnection或者使用[NSURLSession sharedSession]创建的网络请求，调用registerClass方法即可。
[NSURLProtocol registerClass:[NSClassFromString(@"AppDNSInterceptor") class]];
对于基于NSURLSession的网络请求，需要通过配置NSURLSessionConfiguration对象的protocolClasses属性。
NSURLSessionConfiguration *sessionConfiguration = [NSURLSessionConfiguration defaultSessionConfiguration];
sessionConfiguration.protocolClasses = @[[NSClassFromString(@"AppDNSInterceptor") class]];
2.拦截
是否要处理对应的请求。由于网页存在动态链接的可能性，简单的返回YES可能会创建大量的NSURLProtocol对象，因此我们需要保证每个请求能且仅能被返回一次YES.
+(BOOL)canInitWithRequest:(NSURLRequest *)request {}
+(BOOL)canInitWithTask:(NSURLSessionTask *)task { return [self canInitWithRequest:task.currentRequest];}
是否要对请求进行重定向，或者修改请求头、域名等关键信息。返回一个新的NSURLRequest对象来定制业务
+(NSURLRequest *)canonicalRequestForRequest: (NSURLRequest *)request {
//这里截取重定向 做定制化服务:比如修改头部信息 ,dns映射ip等操作
NSMutableURLRequest *mutableRequest = [request mutableCopy];
return mutableRequest;
}
3.转发
-(instancetype)initWithRequest:(NSURLRequest *)request cachedResponse:(NSCachedURLResponse *)cachedResponse client:(id<NSURLProtocolClient>)client {
AppDNSInterceptor *interceptor = [super initWithRequest:request cachedResponse:nil client:client];
return interceptor;}
-(void)startLoading {
NSMutableURLRequest * request = self.request.mutableCopy;
// //给我们处理过的请求设置一个标识符, 防止无限循环,
[NSURLProtocol setProperty: @YES forKey: kAppDNSInterceptorKey inRequest: request];
self.connection = [NSURLConnection connectionWithRequest: request delegate: self];}
4.注回调
当网络收到请求返回时,还需要在将返回值给原来网络请求
-(void)URLProtocol:(NSURLProtocol *)protocol wasRedirectedToRequest:(NSURLRequest *)request redirectResponse:(NSURLResponse *)redirectResponse;
-(void)URLProtocol:(NSURLProtocol *)protocol cachedResponseIsValid:(NSCachedURLResponse *)cachedResponse;
-(void)URLProtocol:(NSURLProtocol *)protocol didReceiveResponse:(NSURLResponse *)response cacheStoragePolicy:(NSURLCacheStoragePolicy)policy;
-(void)URLProtocol:(NSURLProtocol *)protocol didLoadData:(NSData *)data;
-(void)URLProtocolDidFinishLoading:(NSURLProtocol *)protocol;
-(void)URLProtocol:(NSURLProtocol *)protocol didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge;
-(void)URLProtocol:(NSURLProtocol *)protocol didCancelAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge;
5.完结
- (void)stopLoading {
[self.managerSession cancel];
self.managerSession = nil;}
代码不够完善Demo地址--https://github.com/softwarefaith/JiOSDNS
