最近在使用AFNetworking进行网络请求时候出了一个bug解决了很久，打印error 显示Domain=NSCocoaErrorDomain Code=3840，Domain=com.alamofire.error.serialization.response Code=-1011 "Request failed:not found(404)"。一想怎么会404呢。使用的是post请求，请求代码如下：

    AFHTTPSessionManager *manager = [[AFHTTPSessionManager alloc] initWithBaseURL:[NSURL URLWithString:EnergyManagementURL]];
    manager.requestSerializer = [AFJSONRequestSerializer serializer];
    manager.responseSerializer = [AFJSONResponseSerializer serializer];
    manager.responseSerializer.acceptableContentTypes = [NSSet setWithObjects:@"application/json", @"text/json", @"text/javascript", @"text/html",nil];
    [manager POST:postPath parameters:JSONObjectParameter headers:nil progress:nil success:^(NSURLSessionDataTask *task, id responseObject) {
        if (handler) {
            handler(responseObject);
        }
    } failure:^(NSURLSessionDataTask *task, NSError * error) {
        if (failHandler) {
            failHandler();
        }
    }];

后台那边没有问题，用postman测试能拿到数据，但是怎么会404呢，于是就想到会不会是在上传parameter中对manager的设置出来问题。但是发现也没有问题，使用是AFJSONRequestSerializer和AFJSONResponseSerializer而非AFHTTPRequestSerializer与AFHTTPResponseSerializer。后面在多次对照前后台传入的参数后终于找到了问题所在。原因如下：

在NSJSONWritingPrettyPrinted这个模式下，为了好看，其生成的子串是会带空格的，所以造成所编成data之后其长度变长了，服务器那边解析就会出现问题。解决方法是，把这个参数改成0即可。具体修改如下：

    AFJSONRequestSerializer *rqSerializer = [AFJSONRequestSerializer serializerWithWritingOptions:0];//NSJSONWritingPrettyPrinted 设置为0
    rqSerializer.stringEncoding = NSUTF8StringEncoding;

    AFJSONResponseSerializer *rsSerializer = [AFJSONResponseSerializer serializer];
    rsSerializer.stringEncoding = NSUTF8StringEncoding; 
    
    AFHTTPSessionManager *manager = [[AFHTTPSessionManager alloc] initWithBaseURL:[NSURL URLWithString:EnergyManagementURL]];
    manager.requestSerializer = [AFJSONRequestSerializer serializer];
    manager.responseSerializer = [AFJSONResponseSerializer serializer];
    
    manager.responseSerializer.acceptableContentTypes = [NSSet setWithObjects:@"application/json", @"text/json", @"text/javascript", @"text/html",nil];
    [manager POST:postPath parameters:JSONObjectParameter headers:nil progress:nil success:^(NSURLSessionDataTask *task, id responseObject) {
        if (handler) {
            handler(responseObject);
        }
    } failure:^(NSURLSessionDataTask *task, NSError * error) {
        if (failHandler) {
            failHandler();
        }
    }];