Question

我写了以下代码：

                     FileService fileService = FileServiceFactory
                 .getFileService();

                 // Create a new Blob file with mime-type "text/plain"
                 AppEngineFile file = fileService.createNewBlobFile(
                 "image/jpeg", name);

                 if(null!=file)
                 log.warn(file.toString());

                 FileReadChannel readChannel =
                 fileService.openReadChannel(
                 file, true);

                 // Again, different standard Java ways of reading from
                 // the
                 // channel.
                 BufferedReader reader = new BufferedReader(Channels
                 .newReader(readChannel, "UTF8"));
                 String line = reader.readLine();

                 resp.setContentType("text/plain");
                 resp.getWriter().println(line);

                 readChannel.close();

但不幸的是，它给了我以下例外：

来自servlet的未捕获异常 com.google.appengine.api.files.FinalizationException 在com.google.appengine.api.files.FileServiceImpl.translateException（FileServiceImpl.java:597）在com.google.appengine.api.files.FileServiceImpl.makeSyncCall（FileServiceImpl.java:574）在com.google.appengine.api.files.FileServiceImpl.open（FileServiceImpl.java:496）在com.google.appengine.api.files.FileServiceImpl.openForRead（FileServiceImpl.java:456）在com.google.appengine.api.files.FileServiceImpl.openForRead（FileServiceImpl.java:447）在com.google.appengine.api.files.FileServiceImpl.openReadChannel（FileServiceImpl.java:202）在com.myfileshost.MyfileshostServlet.doGet（MyfileshostServlet.java:362）在javax.servlet.http.HttpServlet.service（HttpServlet.java:617）在javax.servlet.http.HttpServlet.service（HttpServlet.java:717）在org.mortbay.jetty.servlet.ServletHolder.handle（ServletHolder.java:511）在org.mortbay.jetty.servlet.ServletHandler $ CachedChain.doFilter（ServletHandler.java:1166）在com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter（ParseBlobUploadFilter.java:102）在org.mortbay.jetty.servlet.ServletHandler $ CachedChain.doFilter（ServletHandler.java:1157）在com.google.apphosting.runtime.jetty.SaveSessionFilter.doFilter（SaveSessionFilter.java:35）在org.mortbay.jetty.servlet.ServletHandler $ CachedChain.doFilter（ServletHandler.java:1157）在com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter（TransactionCleanupFilter.java:43）在org.mortbay.jetty.servlet.ServletHandler $ CachedChain.doFilter（ServletHandler.java:1157）在org.mortbay.jetty.servlet.ServletHandler.handle（ServletHandler.java:388）在org.mortbay.jetty.security.SecurityHandler.handle（SecurityHandler.java:216）在org.mortbay.jetty.servlet.SessionHandler.handle（SessionHandler.java:182）在org.mortbay.jetty.handler.ContextHandler.handle（ContextHandler.java:765）在org.mortbay.jetty.webapp.WebAppContext.handle（WebAppContext.java:418）在com.google.apphosting.runtime.jetty.AppVersionHandlerMap.handle（AppVersionHandlerMap.java:249）在org.mortbay.jetty.handler.HandlerWrapper.handle（HandlerWrapper.java:152）在org.mortbay.jetty.Server.handle（Server.java:326）在org.mortbay.jetty.HttpConnection.handleRequest（HttpConnection.java:542） at org.mortbay.jetty.HttpConnection $ RequestHandler.headerComplete（HttpConnection.java:923）在com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable（RpcRequestParser.java:76）在org.mortbay.jetty.HttpConnection.handle（HttpConnection.java:404）在com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest（JettyServletEngineAdapter.java:135）在com.google.apphosting.runtime.JavaRuntime $ RequestRunnable.run（JavaRuntime.java:446）在com.google.tracing.TraceContext $ TraceContextRunnable.runInContext（TraceContext.java:449）在com.google.tracing.TraceContext $ TraceContextRunnable $ 1.run（TraceContext.java:455）在com.google.tracing.TraceContext.runInContext（TraceContext.java:695）在com.google.tracing.TraceContext $ AbstractTraceContextCallback.runInInheritedContextNoUnref（TraceContext.java:333）在com.google.tracing.TraceContext $ AbstractTraceContextCallback.runInInheritedContext（TraceContext.java:325）在com.google.tracing.TraceContext $ TraceContextRunnable.run（TraceContext.java:453）在com.google.apphosting.runtime.ThreadGroupPool $ PoolEntry.run（ThreadGroupPool.java:251）在java.lang.Thread.run（Thread.java:679）

Answer 1

当通过GAE FileService创建文件时，必须先将其最终确定，然后才能读取。

openReadChannel(..)的Javadoc明确指出，如果文件未最终确定，此方法将抛出FinalizationException。

以下是有关如何创建文件，完成文件然后从中进行阅读的完整示例：https://developers.google.com/appengine/docs/java/blobstore/overview#Writing_Files_to_the_Blobstore

如何按名称检索blobstore文件

1 个答案: