Question

我真的希望你能帮助我！

目标是能够通过我的（java - 谷歌应用引擎）应用程序上传数据文件（.tsv）并获取其内容并将其写入mysql数据库。

经过一番研究，blobstore似乎是最好的选择，因为文件大约是70-100MB。

所以我几天前开始使用这个示例项目让我开始https://github.com/crhym3/java-blobstore-gcs-sample。

我的项目启动并运行没问题。由于我想访问内容而不是下载文件（这是示例项目正在做的事情），我尝试使用BlobstoreInputStream执行此操作，如多个来源中所建议的那样。因此，我从示例项目中更改的唯一文件是ServeBlobServlet。我尝试通过BlobstoreInputStream获取第一行，而不是提供整个blob。

public class ServeBlobServlet extends HttpServlet {

BlobstoreService blobstore = BlobstoreServiceFactory.getBlobstoreService();

private static final Logger log = 
        Logger.getLogger(ServeBlobServlet.class.getName());

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {

    String[] parts = req.getRequestURI().split("/");
    String gsObjectName = URLDecoder.decode(parts[parts.length - 1], "UTF-8");

    log.info("Serving GCS object: " + gsObjectName);
    BlobKey blobKey = blobstore.createGsBlobKey(gsObjectName);

    //blobstore.serve(blobKey, resp);
    System.out.println(getFirstLine(blobKey));
}

private String getFirstLine(BlobKey blobkey) throws IOException {
    BufferedReader reader = new BufferedReader(new InputStreamReader(new BlobstoreInputStream(blobkey)));
    String line = reader.readLine();
    reader.close();
    return line;
}

如你所见。我实际上只是取消注释了blobstore.serve行并添加了标准输出行（并编写了getFirstLine方法）。

虽然我使用与Blobstore.serve相同的BlobKey（工作正常），但我收到此错误。

Uncaught exception from servlet
com.google.appengine.api.blobstore.BlobstoreInputStream$BlobstoreIOException: BlobstoreInputStream received an invalid blob key: AMIfv97t_VDPdp2Qg7UXkE3oc6nRe7yrr86jo6th4-cCU2w8HnjOF5iSOYyAlsrQDkWVLsOMYMdHlbl-AE14swvD5n03N4XStmumVlNeNtNANXI8OWNpodBmJrBB4QS7Ru_AXK5rYvV4-KizTi6kPznYvGQ6gCd1oizh0xtRwO0jkuC-K4l648XpGhZF65H-eb1JJtxWDEsMlQ9LbmRzEPJZHV3tfZ5YRLFnlzOEGnWZxj92BpORnBq8Ly_PMTA-xSNDuFsMBAJwYzdDwG3WVwDpnkxxkqvTLfTRxXKm1WgMZEtlP-0w4NbVwuJ8QNaTAzsDLCs14PFFvWV4pVMd9coXvF3KmC-Z6T4S8yC0nGK9ST0x8o0-CNI
    at com.google.appengine.api.blobstore.BlobstoreInputStream.<init>(BlobstoreInputStream.java:121)
    at com.google.appengine.api.blobstore.BlobstoreInputStream.<init>(BlobstoreInputStream.java:92)
    at com.google.appengine.api.blobstore.BlobstoreInputStream.<init>(BlobstoreInputStream.java:104)
    at com.moviemap.server.ServeBlobServlet.getFirstLine(ServeBlobServlet.java:43)
    at com.moviemap.server.ServeBlobServlet.doGet(ServeBlobServlet.java:39)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
    at com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java:125)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.apphosting.runtime.jetty.SaveSessionFilter.doFilter(SaveSessionFilter.java:37)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.apphosting.utils.servlet.JdbcMySqlConnectionCleanupFilter.doFilter(JdbcMySqlConnectionCleanupFilter.java:60)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
    at com.google.apphosting.runtime.jetty.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:260)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
    at com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable(RpcRequestParser.java:78)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:148)
    at com.google.apphosting.runtime.JavaRuntime$RequestRunnable.run(JavaRuntime.java:469)
    at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:437)
    at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:444)
    at com.google.tracing.CurrentContext.runInContext(CurrentContext.java:234)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:308)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:300)
    at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:441)
    at com.google.apphosting.runtime.ThreadGroupPool$PoolEntry.run(ThreadGroupPool.java:235)
    at java.lang.Thread.run(Thread.java:745)

我尝试了几种不同的方法和BlobKey构造函数，但没有任何作用。同样的错误不断回归。

提前感谢任何花时间帮助的人！欣赏它！

Answer 1

以下是答案

konqi对上述问题的评论绝对正确。我开始使用的项目（链接在问题中）不适合直接上传和读取blob。正如konqi所说，我所做的（项目的作用）是将blob上传到谷歌云存储。

所以回答：如果你想将blob上传到谷歌blobstore并直接阅读，你应该按照这里的教程https://cloud.google.com/appengine/docs/java/blobstore/#Java_Using_the_Blobstore，而不是提供blob（参见教程中的段落），你可以这样读：

    String keyString = req.getParameter("blob-key");
    BlobKey blobkey = new BlobKey(keyString);
    BufferedReader reader = new BufferedReader(new InputStreamReader(new BlobstoreInputStream(blobkey)));
    String line = null;
    while((line = reader.readLine()) != null) {
        //Do whatever you like with the line
    }
    reader.close();

希望这有助于某人

Google App Engine - 使用BlobstoreInputStream逐行读取Blobstore

1 个答案: