最近遇到一个需求：要求从客户端传到服务器的参数是json字符串，于是我本能的用pod装了afn然后进行了request和response Serialization的相关设置

AFHTTPSessionManager *netMnager = [AFHTTPSessionManager manager];netMnager.requestSerializer  = [AFHTTPRequestSerializer serializer];netMnager.responseSerializer = [AFHTTPResponseSerializer serializer];[netMnager.requestSerializer setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];NSDictionary *dicJson =@{@"packetHead": @{@"serviceCode":@"3005",@"token":@"fdsfdsfsfsf8f8dsfsdfsfsfsfsf0dsf0sdf",@"sign":@"FHGHGFHFGHFGHGFHGFHGFHFGHF"},@"packetBody": @{@"abc":@"你好啊"}};[netMnager POST:@"" parameters:dicJson progress:^(NSProgress * _Nonnull uploadProgress) {} success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {}];

在我看来一切都是那么的稀疏平常，可是问题就来了，服务器获取到的数据竟然不是json字符串,而是url编码的格式，也就是&key=value的形式，于是我蒙蔽了，好久没遇到过这种问题了，于是请教了下百度和谷歌，最后研究afn源码发现这是afn设置的原因或者说afn内置的原因

简单的解析下上述代码的运行过程：
1.调用POST方法

2.调用底层URLSESSIONDATATASK

3.创建request对象

4.对request对象进行序列化查询

5.调用对应的request方法

6.AFHttpRequest中的方法执行，其中当没有设置序列化方法时，会走默认的序列化方法，在此方法中最后序列化成为urlencode编码格式，问题也出在此处

最后的优化
第一种方法，设置AFJSONRequetSerializer，此方法中参数以json对象的二进制形式传向后台服务器

  AFHTTPSessionManager *netMnager = [AFHTTPSessionManager manager];
//    netMnager.requestSerializer  = [AFHTTPRequestSerializer serializer];netMnager.requestSerializer  = [AFJSONRequestSerializer serializer];netMnager.responseSerializer = [AFHTTPResponseSerializer serializer];
//    [netMnager.requestSerializer setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
//    [netMnager.requestSerializer setQueryStringSerializationWithBlock:^NSString * _Nonnull(NSURLRequest * _Nonnull request, id  _Nonnull parameters, NSError * _Nullable __autoreleasing * _Nullable error) {
//        NSData *data = [NSJSONSerialization dataWithJSONObject:parameters options:0 error:nil];
//
//        NSString *jsonstr = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
//        NSLog(@"--- %@",jsonstr);
//        return jsonstr;
//    }];NSDictionary *dicJson =@{@"packetHead": @{@"serviceCode":@"3005",@"token":@"fdsfdsfsfsf8f8dsfsdfsfsfsfsf0dsf0sdf",@"sign":@"FHGHGFHFGHFGHGFHGFHGFHFGHF"},@"packetBody": @{@"pageType":@"你好啊"}};[netMnager POST:@"http://192.168.1.7:8888/testgateway" parameters:dicJson progress:^(NSProgress * _Nonnull uploadProgress) {} success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {NSLog(@"---  %@",[NSJSONSerialization JSONObjectWithData:responseObject options:NSJSONReadingMutableContainers error:nil]);} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {NSLog(@"error = %@",error.userInfo);}];

第二种，配置request的序列化查询方法，该方法参数以json字符串的二进制流形式传向服务器

 AFHTTPSessionManager *netMnager = [AFHTTPSessionManager manager];netMnager.requestSerializer  = [AFHTTPRequestSerializer serializer];netMnager.responseSerializer = [AFHTTPResponseSerializer serializer];[netMnager.requestSerializer setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];[netMnager.requestSerializer setQueryStringSerializationWithBlock:^NSString * _Nonnull(NSURLRequest * _Nonnull request, id  _Nonnull parameters, NSError * _Nullable __autoreleasing * _Nullable error) {NSData *data = [NSJSONSerialization dataWithJSONObject:parameters options:0 error:nil];NSString *jsonstr = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];NSLog(@"--- %@",jsonstr);return jsonstr;}];NSDictionary *dicJson =@{@"packetHead": @{@"serviceCode":@"3005",@"token":@"fdsfdsfsfsf8f8dsfsdfsfsfsfsf0dsf0sdf",@"sign":@"FHGHGFHFGHFGHGFHGFHGFHFGHF"},@"packetBody": @{@"pageType":@"你好啊"}};[netMnager POST:@"http://192.168.1.7:8888/testgateway" parameters:dicJson progress:^(NSProgress * _Nonnull uploadProgress) {} success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {NSLog(@"---  %@",[NSJSONSerialization JSONObjectWithData:responseObject options:NSJSONReadingMutableContainers error:nil]);} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {NSLog(@"error = %@",error.userInfo);}];