设计：

首先，本地保存一份初始的DNS Json文件

使用

直接替换IP

NSString *originUrlString = [request.URL absoluteString];
    NSString *originHostString = [request.URL host];
    NSRange hostRange = [originUrlString rangeOfString:originHostString];
    if (hostRange.location != NSNotFound) { 
    	 NSString *ip = [[CustomDNSManager sharedClient] requestIPWithHost:originHostString];
    }

以下只拦截请求，不修改请求

若要修改，修改RichURLSessionProtocol中的canonicalRequestForRequest方法

全局拦截

不包含单独的session和AFN

 -(BOOL)application:(UIApplication *)application 
 didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
	[NSURLProtocol registerClass:[RichURLSessionProtocol class]];
}

UIWebView拦截

期间的接口请求也会被拦截 页面初始化时

- (void)viewDidLoad {
    [super viewDidLoad];
    [NSURLProtocol registerClass:[RichURLSessionProtocol class]];
}

页面销毁

- (void)dealloc {
    
    [NSURLProtocol unregisterClass:[RichURLSessionProtocol class]];
}

AFN拦截或者NSURLSessionConfiguration

	NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
	NSArray *protocolClasses = @[[RichURLSessionProtocol class]];
	config.protocolClasses = protocolClasses;
	AFHTTPSessionManager *manage = [[AFHTTPSessionManager alloc] initWithSessionConfiguration:config];

WKWebview

• [Github:NSURLProtocol-WebKitSupport] (https://github.com/Yeatse/NSURLProtocol-WebKitSupport)

参考文献：

• [可能是最全的iOS端HttpDns集成方案] (https://www.jianshu.com/p/cd4c1bf1fd5f)
• NSURLPtotocol无法拦截AFN ,WKWebView