AFNetworking 3.0 源码解析之Serializat

作者: SemyonXu | 来源:发表于2016-10-07 21:34 被阅读345次

本部分主要的作用：网络通信信息序列化/反序列化

AFURLRequestSerialization

功能：

负责参数转换成NSMutableURLRequest类型，进行网络请求。

构建普通请求：格式化请求参数，生成HTTP Header
构建multipart请求

类关系：

父类：

AFHTTPRequestSerializer,二进制格式（query字符串转换成二进制）

子类：

AFJSONRequestSerializer,Json格式（Json序列化成NSData类型）
AFPropertyListRequestSerializer，Plist（一种特殊的XML，解析起来相对容易）

封装思路：

所有类遵循一个协议AFURLRequestSerialization，协议中一个非必须实现的方法：

 - (nullableNSURLRequest*)requestBySerializingRequest:(NSURLRequest*)request
                                 withParameters:(nullableid)parameters
                                    error:(NSError* _Nullable__autoreleasing *)error NS_SWIFT_NOTHROW;

父类AFHTTPRequestSerializer中提供外部调用接口：

- (NSMutableURLRequest*)requestWithMethod:(NSString*)method
                                 URLString:(NSString*)URLString
                                parameters:(id)parameters
                                     error:(NSError*__autoreleasing*)error

在这个方法中调用协议方法：

mutableRequest = [[selfrequestBySerializingRequest:mutableRequestwithParameters:parameterserror:error]mutableCopy];

而这个方法的实现是父类以及各个子类分别实现。所以，此处self如果是AFHTTPRequestSerializer那么走AFHTTPRequestSerializer类下的实现，如果是
AFJSONRequestSerializer，那么走AFJSONRequestSerializer类下的实现。然后再分别实现这个方法不同功能的实现。

下面看一下各个类不同职能分别的实现：

AFURLRequestSerialization中的实现:

- (NSURLRequest *)requestBySerializingRequest:(NSURLRequest *)request
                               withParameters:(id)parameters
                                        error:(NSError *__autoreleasing *)error
{
    NSParameterAssert(request);

    NSMutableURLRequest *mutableRequest = [requestmutableCopy];

    [self.HTTPRequestHeadersenumerateKeysAndObjectsUsingBlock:^(id field,id value, BOOL *__unused stop) {
        if (![requestvalueForHTTPHeaderField:field]) {
            [mutableRequest setValue:valueforHTTPHeaderField:field];
        }
    }];

    NSString *query =nil;
    if (parameters) {
        if (self.queryStringSerialization) {
            NSError *serializationError;
            query = self.queryStringSerialization(request, parameters, &serializationError);

            if (serializationError) {
                if (error) {
                    *error = serializationError;
                }

                returnnil;
            }
        } else {
            switch (self.queryStringSerializationStyle) {
                caseAFHTTPRequestQueryStringDefaultStyle:
                    query = AFQueryStringFromParameters(parameters);
                    break;
            }
        }
    }

    if ([self.HTTPMethodsEncodingParametersInURIcontainsObject:[[request HTTPMethod]uppercaseString]]) { //普通GET，HEAD等，参数直接拼接在url后面用&分开
        if (query && query.length >0) {
            mutableRequest.URL = [NSURLURLWithString:[[mutableRequest.URLabsoluteString] stringByAppendingFormat:mutableRequest.URL.query ? @"&%@" : @"?%@", query]];
        }
    } else {
        // #2864: an empty string is a valid x-www-form-urlencoded payload
        if (!query) {
            query = @"";
        }
        if (![mutableRequestvalueForHTTPHeaderField:@"Content-Type"]) {
            [mutableRequest setValue:@"application/x-www-form-urlencoded"forHTTPHeaderField:@"Content-Type"];
        }
        [mutableRequest setHTTPBody:[querydataUsingEncoding:self.stringEncoding]];// 普通的POST请求参数，直接转换成NSData设置到HTTP的body中。
    }

    return mutableRequest;
}

我们可以看到AFNetworking对于GET，POST请求参数的处理，一个是直接拼接在URL上面，一个是设置在HTTPBody里面。

其中，HTTPMethodsEncodingParametersInURI的初始化如下：

self.HTTPMethodsEncodingParametersInURI = [NSSet setWithObjects:@"GET", @"HEAD", @"DELETE", nil]; // 支持GET，HEAD，DELETE

也就是GET,HEAD,DELETE支持的是参数直接拼接URL的方式。

AFJSONRequestSerialization中的实现:

- (NSURLRequest *)requestBySerializingRequest:(NSURLRequest *)request
                               withParameters:(id)parameters
                                        error:(NSError *__autoreleasing *)error
{
    NSParameterAssert(request);

    if ([self.HTTPMethodsEncodingParametersInURI containsObject:[[request HTTPMethod] uppercaseString]]) {
        return [super requestBySerializingRequest:request withParameters:parameters error:error];
    }

    NSMutableURLRequest *mutableRequest = [request mutableCopy];

    [self.HTTPRequestHeaders enumerateKeysAndObjectsUsingBlock:^(id field, id value, BOOL * __unused stop) {
        if (![request valueForHTTPHeaderField:field]) {
            [mutableRequest setValue:value forHTTPHeaderField:field];
        }
    }]; // 设置公共的请求头

    if (parameters) {
        if (![mutableRequest valueForHTTPHeaderField:@"Content-Type"]) {
            [mutableRequest setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
        }

        [mutableRequest setHTTPBody:[NSJSONSerialization dataWithJSONObject:parameters options:self.writingOptions error:error]];
    }

    return mutableRequest;
}

跟AFURLRequestSerialization中的实现差不多，如果是HTTPMethodsEncodingParametersInURI请求方式是GET，HEAD，DELETE，则直接调用父类的解析方法。如果是POST等其他的，那么做了一下设置请求头Content-Type = “application/json”,并且将paramters参数Json序列化成NSData,设置到HTTPBody里面。

AFPropertyListRequestSerialization中的实现:

- (NSURLRequest *)requestBySerializingRequest:(NSURLRequest *)request
                               withParameters:(id)parameters
                                        error:(NSError *__autoreleasing *)error
{
    NSParameterAssert(request);

    if ([self.HTTPMethodsEncodingParametersInURI containsObject:[[request HTTPMethod] uppercaseString]]) {
        return [super requestBySerializingRequest:request withParameters:parameters error:error];
    }

    NSMutableURLRequest *mutableRequest = [request mutableCopy];

    [self.HTTPRequestHeaders enumerateKeysAndObjectsUsingBlock:^(id field, id value, BOOL * __unused stop) {
        if (![request valueForHTTPHeaderField:field]) {
            [mutableRequest setValue:value forHTTPHeaderField:field];
        }
    }];

    if (parameters) {
        if (![mutableRequest valueForHTTPHeaderField:@"Content-Type"]) {
            [mutableRequest setValue:@"application/x-plist" forHTTPHeaderField:@"Content-Type"];
        }

        [mutableRequest setHTTPBody:[NSPropertyListSerialization dataWithPropertyList:parameters format:self.format options:self.writeOptions error:error]];
    }

    return mutableRequest;
}

好吧，封装思路跟AFJSONRequestSerialization一样，区别在于json序列化变成Plist的转换。

AFURLResponseSerialization

功能：

负责对网络请求返回的数据进行解析。

类关系：

父类：

AFHTTPResponseSerializer，二进制格式

子类：

AFJSONResponseSerializer, JSON格式
AFXMLParseResponseSerializer, XML（只能返回XMLParser，还需要自己通过代理解析）
AFXMLDocumentResponseSerializer, （Mac OS X）
AFPropertyListResponseSerializer, Plist
AFImageResponseSerializer, Image
AFCompoundResponseSerializer, 组合

封装思路：

跟Request的封装思路基本相同。只不过这个是在数据请求到之后进行的处理。遵循的是AFURLResponseSerialization协议。实现方法：

- (id)responseObjectForResponse:(NSURLResponse *)response
                           data:(NSData *)data
                          error:(NSError *__autoreleasing *)error

此处的返回值是id类型的，也就是数据解析完之后的数据。

顺便提一下返回值解析的调用函数是在AFURLSessionManager中的网络请求成功的回调中：

- (void)URLSession:(__unused NSURLSession *)session
              task:(NSURLSessionTask *)task
didCompleteWithError:(NSError *)error
{
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wgnu"
    __strong AFURLSessionManager *manager = self.manager;

    __block id responseObject = nil;

    __block NSMutableDictionary *userInfo = [NSMutableDictionary dictionary];
    userInfo[AFNetworkingTaskDidCompleteResponseSerializerKey] = manager.responseSerializer;

    //Performance Improvement from #2672
    NSData *data = nil;
    if (self.mutableData) {
        data = [self.mutableData copy];
        //We no longer need the reference, so nil it out to gain back some memory.
        self.mutableData = nil;
    }

    if (self.downloadFileURL) {
        userInfo[AFNetworkingTaskDidCompleteAssetPathKey] = self.downloadFileURL;
    } else if (data) {
        userInfo[AFNetworkingTaskDidCompleteResponseDataKey] = data;
    }

    if (error) {
        userInfo[AFNetworkingTaskDidCompleteErrorKey] = error;

        dispatch_group_async(manager.completionGroup ?: url_session_manager_completion_group(), manager.completionQueue ?: dispatch_get_main_queue(), ^{
            if (self.completionHandler) {
                self.completionHandler(task.response, responseObject, error);
            }

            dispatch_async(dispatch_get_main_queue(), ^{
                [[NSNotificationCenter defaultCenter] postNotificationName:AFNetworkingTaskDidCompleteNotification object:task userInfo:userInfo];
            });
        });
    } else {
        dispatch_async(url_session_manager_processing_queue(), ^{
            NSError *serializationError = nil;
            responseObject = [manager.responseSerializer responseObjectForResponse:task.response data:data error:&serializationError]; // 此处进行数据的解析

            if (self.downloadFileURL) {
                responseObject = self.downloadFileURL;
            }

            if (responseObject) {
                userInfo[AFNetworkingTaskDidCompleteSerializedResponseKey] = responseObject;
            }

            if (serializationError) {
                userInfo[AFNetworkingTaskDidCompleteErrorKey] = serializationError;
            }

            dispatch_group_async(manager.completionGroup ?: url_session_manager_completion_group(), manager.completionQueue ?: dispatch_get_main_queue(), ^{
                if (self.completionHandler) {
                    self.completionHandler(task.response, responseObject, serializationError);
                }

                dispatch_async(dispatch_get_main_queue(), ^{
                    [[NSNotificationCenter defaultCenter] postNotificationName:AFNetworkingTaskDidCompleteNotification object:task userInfo:userInfo];
                });
            });
        });
    }
#pragma clang diagnostic pop
}

下面看一下各个类不同职能分别的实现：
父类AFHTTPResponseSerializer 中的实现：

- (id)responseObjectForResponse:(NSURLResponse *)response
                           data:(NSData *)data
                          error:(NSError *__autoreleasing *)error
{
    [self validateResponse:(NSHTTPURLResponse *)response data:data error:error];

    return data;
}

此处就一个方法，就是做了一个返回的数据是否有效。但是数据是否有错，都会返回原始数据，没有做任何的修改。
看一下返回数据有效性的方法实现：

- (BOOL)validateResponse:(NSHTTPURLResponse *)response
                    data:(NSData *)data
                   error:(NSError * __autoreleasing *)error
{
    BOOL responseIsValid = YES;
    NSError *validationError = nil;

    if (response && [response isKindOfClass:[NSHTTPURLResponse class]]) {
        if (self.acceptableContentTypes && ![self.acceptableContentTypes containsObject:[response MIMEType]] &&
            !([response MIMEType] == nil && [data length] == 0)) {

            if ([data length] > 0 && [response URL]) {
                NSMutableDictionary *mutableUserInfo = [@{
                                                          NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Request failed: unacceptable content-type: %@", @"AFNetworking", nil), [response MIMEType]],
                                                          NSURLErrorFailingURLErrorKey:[response URL],
                                                          AFNetworkingOperationFailingURLResponseErrorKey: response,
                                                        } mutableCopy];
                if (data) {
                    mutableUserInfo[AFNetworkingOperationFailingURLResponseDataErrorKey] = data;
                }

                validationError = AFErrorWithUnderlyingError([NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorCannotDecodeContentData userInfo:mutableUserInfo], validationError);
            }

            responseIsValid = NO;
        }

        if (self.acceptableStatusCodes && ![self.acceptableStatusCodes containsIndex:(NSUInteger)response.statusCode] && [response URL]) {
            NSMutableDictionary *mutableUserInfo = [@{
                                               NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Request failed: %@ (%ld)", @"AFNetworking", nil), [NSHTTPURLResponse localizedStringForStatusCode:response.statusCode], (long)response.statusCode],
                                               NSURLErrorFailingURLErrorKey:[response URL],
                                               AFNetworkingOperationFailingURLResponseErrorKey: response,
                                       } mutableCopy];

            if (data) {
                mutableUserInfo[AFNetworkingOperationFailingURLResponseDataErrorKey] = data;
            }

            validationError = AFErrorWithUnderlyingError([NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorBadServerResponse userInfo:mutableUserInfo], validationError);

            responseIsValid = NO;
        }
    }

    if (error && !responseIsValid) {
        *error = validationError;
    }

    return responseIsValid;
}

这里主要做了判断是不是支持的返回content-type类型，再就是状态码是不是200+，如果不满足就不是有效的返回数据。
看下初始化值：

self.acceptableContentTypes = [NSSet setWithObjects:@"application/json", @"text/json", @"text/javascript", nil];
self.acceptableStatusCodes = [NSIndexSet indexSetWithIndexesInRange:NSMakeRange(200, 100)];

子类AFJSONResponseSerializer中的实现：

- (id)responseObjectForResponse:(NSURLResponse *)response
                           data:(NSData *)data
                          error:(NSError *__autoreleasing *)error
{
    if (![self validateResponse:(NSHTTPURLResponse *)response data:data error:error]) {
        if (!error || AFErrorOrUnderlyingErrorHasCodeInDomain(*error, NSURLErrorCannotDecodeContentData, AFURLResponseSerializationErrorDomain)) {
            return nil;
        }
    }

    id responseObject = nil;
    NSError *serializationError = nil;
    // Workaround for behavior of Rails to return a single space for `head :ok` (a workaround for a bug in Safari), which is not interpreted as valid input by NSJSONSerialization.
    // See https://github.com/rails/rails/issues/1742
    BOOL isSpace = [data isEqualToData:[NSData dataWithBytes:" " length:1]];
    if (data.length > 0 && !isSpace) {
        responseObject = [NSJSONSerialization JSONObjectWithData:data options:self.readingOptions error:&serializationError];
    } else {
        return nil;
    }

    if (self.removesKeysWithNullValues && responseObject) {
        responseObject = AFJSONObjectByRemovingKeysWithNullValues(responseObject, self.readingOptions);
    }

    if (error) {
        *error = AFErrorWithUnderlyingError(serializationError, *error);
    }

    return responseObject;
}

此处看到在父类中对有效性的判断结果并没有做处理，而在Json转换类中，如果返回数据是无效的，直接就返回nil。然后就是对返回数据进行了Json转换。并对结果进行了空值进行了排空。

其他的子类的封装思路也都相似，不再一一赘述。注意的是不同的功能的子类对返回值的类型支持是不同的。

如果文中有什么错误，欢迎大家指正。

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AFNetworking 3.0 源码解析之Serializat

AFURLRequestSerialization

功能：

类关系：

封装思路：

AFURLResponseSerialization

功能：

类关系：

封装思路：

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