如何从 Google App Engine 访问 CSV 数据？

Question

我有一个简单的网络应用程序，可让用户将 CSV 上传到 GAE blob 存储。我正在尝试将该数据传递给谷歌分析 API 方法，但我无法弄清楚如何。按照教程文档，我似乎只能在响应头中返回文件。

有没有办法将 blob 作为文件直接传递给方法？

或者，有没有办法上传 blob，然后将数据映射到 Cloud Storage？

Answer 1

如果您按照此处的代码https://cloud.google.com/appengine/docs/java/blobstore/ 操作，它将指导您设置上传 URL 并提供回调 URL 等...当文件上传并调用您的回调 URL 时，您需要记住 blob 键，您可以将其保存在数据存储中，将其保留在会话中或根据需要从数据存储中读取 blob。

下面的代码应该会有所帮助，特别是您感兴趣的方法是 getBlobAsString 或者您可以简单地使用 blobStream (BlobstoreInputStream blobStream = new BlobstoreInputStream(blobKey);)将文件内容作为 InputStream 传递

在您的 servlet 中处理上传回调

import org.apache.commons.io.IOUtils;

import com.google.appengine.api.blobstore.BlobKey;
import com.google.appengine.api.blobstore.BlobstoreInputStream;
import com.google.appengine.api.blobstore.BlobstoreService;
import com.google.appengine.api.blobstore.BlobstoreServiceFactory;

public class Upload extends HttpServlet {
    private BlobstoreService blobstoreService = BlobstoreServiceFactory.getBlobstoreService();

    @Override
    public void doPost(HttpServletRequest req, HttpServletResponse res)
        throws ServletException, IOException {

        Map<String, BlobKey> blobs = blobstoreService.getUploadedBlobs(req);
        BlobKey blobKey = blobs.get("myFile");

        if (blobKey != null) {
            String keyString = blobKey.getKeyString();
            // you can store keyString in the datastore or whatever
            // if you want the call the analytics API then you need the blob as string

             String csv = getBlobAsString(keyString);

             // you can do with csv whatever you like, convert it as an array, etc... then pass it
             // over to the analytic API
        } 
    }


   public static String getBlobAsString(String keyString) throws IOException {
        BlobKey blobKey = new BlobKey(keyString);
        BlobstoreInputStream blobStream = new BlobstoreInputStream(blobKey);

        return IOUtils.toString(blobStream, "UTF-8");
    }
 }