WiFi文件上传框架SGWiFiUpload

背景

在iOS端由于文件系统的封闭性，文件的上传变得十分麻烦，一个比较好的解决方案是通过局域网WiFi来传输文件并存储到沙盒中。

简介

SGWiFiUpload是一个基于CocoaHTTPServer的WiFi上传框架。CocoaHTTPServer是一个可运行于iOS和OS X上的轻量级服务端框架，可以处理GET和POST请求，通过对代码的初步改造，实现了iOS端的WiFi文件上传与上传状态监听。

下载与使用

目前已经做成了易用的框架，上传到了GitHub，点击这里进入，欢迎Star！

请求的处理

CocoaHTTPServer通过HTTPConnection这一接口实现类来回调网络请求的各个状态，包括对请求头、响应体的解析等。为了实现文件上传，需要自定义一个继承HTTPConnection的类，这里命名为SGHTTPConnection，与文件上传有关的几个方法如下。

解析文件上传的请求头

- (void)processStartOfPartWithHeader:(MultipartMessageHeader*) header {

    // in this sample, we are not interested in parts, other then file parts.
    // check content disposition to find out filename

    MultipartMessageHeaderField* disposition = [header.fields objectForKey:@"Content-Disposition"];
    NSString* filename = [[disposition.params objectForKey:@"filename"] lastPathComponent];

    if ( (nil == filename) || [filename isEqualToString: @""] ) {
        // it's either not a file part, or
        // an empty form sent. we won't handle it.
        return;
    }
    // 这里用于发出文件开始上传的通知
    dispatch_async(dispatch_get_main_queue(), ^{
        [[NSNotificationCenter defaultCenter] postNotificationName:SGFileUploadDidStartNotification object:@{@"fileName" : filename ?: @"File"}];
    });
    // 这里用于设置文件的保存路径，先预存一个空文件，然后进行追加写内容
    NSString *uploadDirPath = [SGWiFiUploadManager sharedManager].savePath;
    BOOL isDir = YES;
    if (![[NSFileManager defaultManager]fileExistsAtPath:uploadDirPath isDirectory:&isDir ]) {
        [[NSFileManager defaultManager]createDirectoryAtPath:uploadDirPath withIntermediateDirectories:YES attributes:nil error:nil];
    }

    NSString* filePath = [uploadDirPath stringByAppendingPathComponent: filename];
    if( [[NSFileManager defaultManager] fileExistsAtPath:filePath] ) {
        storeFile = nil;
    }
    else {
        HTTPLogVerbose(@"Saving file to %@", filePath);
        if(![[NSFileManager defaultManager] createDirectoryAtPath:uploadDirPath withIntermediateDirectories:true attributes:nil error:nil]) {
            HTTPLogError(@"Could not create directory at path: %@", filePath);
        }
        if(![[NSFileManager defaultManager] createFileAtPath:filePath contents:nil attributes:nil]) {
            HTTPLogError(@"Could not create file at path: %@", filePath);
        }
        storeFile = [NSFileHandle fileHandleForWritingAtPath:filePath];
        [uploadedFiles addObject: [NSString stringWithFormat:@"/upload/%@", filename]];
    }
}

其中有中文注释的两处是比较重要的地方，这里根据请求头发出了文件开始上传的通知，并且往要存放的路径写一个空文件，以便后续追加内容。

上传过程中的处理

- (void) processContent:(NSData*) data WithHeader:(MultipartMessageHeader*) header 
{
    // here we just write the output from parser to the file.
    // 由于除去文件内容外，还有HTML内容和空文件通过此方法处理，因此需要过滤掉HTML和空文件内容
    if (!header.fields[@"Content-Disposition"]) {
        return;
    } else {
        MultipartMessageHeaderField *field = header.fields[@"Content-Disposition"];
        NSString *fileName = field.params[@"filename"];
        if (fileName.length == 0) return;
    }
    self.currentLength += data.length;
    CGFloat progress;
    if (self.contentLength == 0) {
        progress = 1.0f;
    } else {
        progress = (CGFloat)self.currentLength / self.contentLength;
    }
    dispatch_async(dispatch_get_main_queue(), ^{
       [[NSNotificationCenter defaultCenter] postNotificationName:SGFileUploadProgressNotification object:@{@"progress" : @(progress)}]; 
    });
    if (storeFile) {
        [storeFile writeData:data];
    }
}

这里除了拼接文件内容以外，还发出了上传进度的通知，当前方法中只能拿到这一段文件的长度，总长度需要通过下面的方法拿到。

获取文件大小

- (void)prepareForBodyWithSize:(UInt64)contentLength
{
    HTTPLogTrace();
    // 设置文件总大小，并初始化当前已经传输的文件大小。
    self.contentLength = contentLength;
    self.currentLength = 0;
    // set up mime parser
    NSString* boundary = [request headerField:@"boundary"];
    parser = [[MultipartFormDataParser alloc] initWithBoundary:boundary formEncoding:NSUTF8StringEncoding];
    parser.delegate = self;

    uploadedFiles = [[NSMutableArray alloc] init];
}

处理传输完毕

- (void) processEndOfPartWithHeader:(MultipartMessageHeader*) header
{
    // as the file part is over, we close the file.
    // 由于除去文件内容外，还有HTML内容和空文件通过此方法处理，因此需要过滤掉HTML和空文件内容
    if (!header.fields[@"Content-Disposition"]) {
        return;
    } else {
        MultipartMessageHeaderField *field = header.fields[@"Content-Disposition"];
        NSString *fileName = field.params[@"filename"];
        if (fileName.length == 0) return;
    }
    [storeFile closeFile];
    storeFile = nil;
    dispatch_async(dispatch_get_main_queue(), ^{
        [[NSNotificationCenter defaultCenter] postNotificationName:SGFileUploadDidEndNotification object:nil];
    });
}

这里关闭了文件管道，并且发出了文件上传完毕的通知。

开启Server

CocoaHTTPServer默认的Web根目录为MainBundle，他会在目录下寻找index.html，文件上传的请求地址为upload.html，当以POST方式请求upload.html时，请求会被Server拦截，并且交由HTTPConnection处理。

- (BOOL)startHTTPServerAtPort:(UInt16)port {
    HTTPServer *server = [HTTPServer new];
    server.port = port;
    self.httpServer = server;
    [self.httpServer setDocumentRoot:self.webPath];
    [self.httpServer setConnectionClass:[SGHTTPConnection class]];
    NSError *error = nil;
    [self.httpServer start:&error];
    return error == nil;
}

在HTML中发送POST请求上传文件

在CocoaHTTPServer给出的样例中有用于文件上传的index.html，要实现文件上传，只需要一个POST方法的form表单，action为upload.html，每一个文件使用一个input标签，type为file即可，这里为了美观对input标签进行了自定义。
下面的代码演示了能同时上传3个文件的index.html代码。

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
    <head>
        <meta http-equiv=\"content-type\" content=\"text/html; charset=UTF-8\">
    </head>
    <style>
    body {
        margin: 0px;
        padding: 0px;
        font-size: 12px;
        background-color: rgb(244,244,244);
        text-align: center;
    }
    #container {
        margin: auto;
    }

    #form {
        margin-top: 60px;
    }

    .upload {
        margin-top: 2px;
    }

    #submit input {
        background-color: #ea4c88;
        color: #eee;
        font-weight: bold;
        margin-top: 10px;
        text-align: center;
        font-size: 16px;
        border: none;
        width: 120px;
        height: 36px;
    }

    #submit input:hover {
        background-color: #d44179;
    }

    #submit input:active {
        background-color: #a23351;
    }

    .uploadField {
        margin-top: 2px;
        width: 200px;
        height: 22px;
        font-size: 12px;
    }

    .uploadButton {
        background-color: #ea4c88;
        color: #eee;
        font-weight: bold;
        text-align: center;
        font-size: 15px;
        border: none;
        width: 80px;
        height: 26px;
    }

    .uploadButton:hover {
        background-color: #d44179;
    }

    .uploadButton:active {
        background-color: #a23351;
    }

    </style>
    <body>
        <div id="container">
            <div id="form">
                <h2>WiFi File Upload</h2>
                <form name="form" action="upload.html" method="post" enctype="multipart/form-data" accept-charset="utf-8">
                    <div class="upload">
                        <input type="file" name="upload1" id="upload1" style="display:none" onChange="document.form.path1.value=this.value">
                            <input class="uploadField" name="path1" readonly>
                                <input class="uploadButton" type="button" value="Open" onclick="document.form.upload1.click()">
                    </div>
                    <div class="upload">
                        <input type="file" name="upload2" id="upload2" style="display:none" onChange="document.form.path2.value=this.value">
                            <input class="uploadField" name="path2" readonly>
                                <input class="uploadButton" type="button" value="Open" onclick="document.form.upload2.click()">
                    </div>
                    <div class="upload">
                        <input type="file" name="upload3" id="upload3" style="display:none" onChange="document.form.path3.value=this.value">
                            <input class="uploadField" name="path3" readonly>
                                <input class="uploadButton" type="button" value="Open" onclick="document.form.upload3.click()">
                                    </div>
                    <div id="submit"><input type="submit" value="Submit"></div>
                </form>
            </div>
        </div>
    </body>
</html>

表单提交后，会进入upload.html页面，该页面用于说明上传完毕，下面的代码实现了3秒后的重定向返回。

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
    <head>
        <meta http-equiv=\"content-type\" content=\"text/html; charset=UTF-8\">
        <meta http-equiv=refresh content="3;url=index.html">
    </head>
    <body>
        <h3>Upload Succeeded!</h3>
        <p>The Page will be back in 3 seconds</p>
    </body>
</html>