axios文件下载的各种方法

àì夳堔傛蜴生んèń 2022-12-01 14:20 729阅读 0赞

## axios ##

查看源码发现axios返回的内容默认是Stream格式的；

如果没有设置responseType的话，返回内容将会从Stream转为Buffer再转为String；

如果responseType为stream的话不进行转换；

如果responseType为arraybuffer的话将Stream转为Buffer；

但是如果想把Buffer转为String再转回Buffer的话将会出问题(默认使用utf8进行Buffer的编码和解码)，有的文件这样是可以的，但是Excel文件这样做的话两次Buffer的值是不同的；但是转为base64的话是都可以的。

### 方法一：设置responseType为stream ###

const result = await require('axios')({ url, method, data, responseType: 'stream' });
    result.data.pipe(require('fs').createWriteStream(saveFilePath));

### 提供buffer转Stream并保存为文件的方法 ###

### 方法二：设置responseType为arraybuffer ###

const result = await require('axios')({ url, method, data, responseType: 'arraybuffer' });
    const bufferData = result.data;
    await bufferToStream(bufferData, saveFilePath);

### 方法三：不设置responseType，设置responseEncoding为base64 ###

const result = await require('axios')({ url, method, data, responseEncoding: 'base64' });
    const bufferData = Buffer.from(result.data, 'base64');
    await bufferToStream(bufferData, saveFilePath);

### 附上axios相关源码 ###

/adapters/http.js
    
    
    var req = transport.request(options, function handleResponse(res) {
      if (req.aborted) return;
    
      // uncompress the response body transparently if required
      var stream = res;
      switch (res.headers['content-encoding']) {
      /*eslint default-case:0*/
      case 'gzip':
      case 'compress':
      case 'deflate':
        // add the unzipper to the body stream processing pipeline
        stream = (res.statusCode === 204) ? stream : stream.pipe(zlib.createUnzip());
    
        // remove the content-encoding in order to not confuse downstream operations
        delete res.headers['content-encoding'];
        break;
      }
    
      // return the last request in case of redirects
      var lastRequest = res.req || req;
    
      var response = {
        status: res.statusCode,
        statusText: res.statusMessage,
        headers: res.headers,
        config: config,
        request: lastRequest
      };
      if (config.responseType === 'stream') {
        response.data = stream;
        settle(resolve, reject, response);
      } else {
        var responseBuffer = [];
        stream.on('data', function handleStreamData(chunk) {
          responseBuffer.push(chunk);
    
          // make sure the content length is not over the maxContentLength if specified
          if (config.maxContentLength > -1 && Buffer.concat(responseBuffer).length > config.maxContentLength) {
            stream.destroy();
            reject(createError('maxContentLength size of ' + config.maxContentLength + ' exceeded',
              config, null, lastRequest));
          }
        });
    
        stream.on('error', function handleStreamError(err) {
          if (req.aborted) return;
          reject(enhanceError(err, config, null, lastRequest));
        });
    
        stream.on('end', function handleStreamEnd() {
          var responseData = Buffer.concat(responseBuffer);
          if (config.responseType !== 'arraybuffer') {
            responseData = responseData.toString(config.responseEncoding);
          }
          response.data = responseData;
          settle(resolve, reject, response);
        });
      }
    });