//GET方式获取百度主页内容
NSString *url = [NSString stringWithFormat:@"http://www.baidu.com"];
AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
manager.responseSerializer = [AFHTTPResponseSerializer serializer];

[manager.responseSerializer setAcceptableContentTypes:[NSSet setWithObjects:@"text/html", nil]];
[manager GET:url parameters:nil progress:nil success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {

    NSString *result = [[NSString alloc]initWithData:responseObject encoding:NSUTF8StringEncoding];
    NSLog(@"%@",result);
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
    NSLog(@"%@",[error localizedDescription]);
}];