使用AFNetWorking进行POST JSON 请求出现问题

使用AFNetWorking进行POST JSON请求不通时

头部请求更换为：

 [mgr.requestSerializer setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];

AFURLRequestSerialization类中104行更换为：

// 源代码
//- (NSString *)URLEncodedStringValue {
//    if (!self.value || [self.value isEqual:[NSNull null]]) {
//        return AFPercentEscapedStringFromString([self.field description]);
//    } else {
//        return [NSString stringWithFormat:@"%@=%@", AFPercentEscapedStringFromString([self.field description]), AFPercentEscapedStringFromString([self.value description])];
//    }
//}

- (NSString *)URLEncodedStringValue {
   if (!self.value || [self.value isEqual:[NSNull null]]) {
        return AFPercentEscapedStringFromString([self.field description]);
    }else if(!self.field || [self.field isEqual:[NSNull null]]){
        return [NSString stringWithFormat:@"%@",self.value];
    }else {
        return [NSString stringWithFormat:@"%@=%@", AFPercentEscapedStringFromString([self.field description]), AFPercentEscapedStringFromString([self.value description])];
    }
}