Major Description
I’m implementing a web service to upload files (from 120 Kb to 1 Mb). Most of the time everything works fine, but sometimes (randomly) the uploaded file is empty (size == 0) in the target platform.
After some debugging I found that the problem comes from the temp file created by the CachedOutputStream that is deleted during the process of getting the cached stream. In fact, maybeDeleteTempFile is called before getInputStream which returns an empty LoadingByteArrayOutputStream. The finalize method of FileInputStream calls its close method which is overridden in CachedOutputStream#getInputStream to delete the temp file.
I tried to synchronize all the methods dealing with tempFile but it didn’t resolve my problem.
The stack:
Daemon System Thread [Finalizer] (Suspended (breakpoint at line 490 in CachedOutputStream)) CachedOutputStream.maybeDeleteTempFile(Object) line: 490 CachedOutputStream.access$000(CachedOutputStream, Object) line: 43 CachedOutputStream$1.close() line: 469 CachedOutputStream$1(FileInputStream).finalize() line: 381 Finalizer.invokeFinalizeMethod(Object) line: not available [native method] Finalizer.runFinalizer() line: 83 Finalizer.access$100(Finalizer) line: 14 Finalizer$FinalizerThread.run() line: 160
The getInputStream method:
public InputStream getInputStream() throws IOException { flush(); if (inmem) { if (currentStream instanceof LoadingByteArrayOutputStream) { return ((LoadingByteArrayOutputStream) currentStream).createInputStream(); } else if (currentStream instanceof ByteArrayOutputStream) { return new ByteArrayInputStream(((ByteArrayOutputStream) currentStream).toByteArray()); } else if (currentStream instanceof PipedOutputStream) { return new PipedInputStream((PipedOutputStream) currentStream); } else { return null; } } else { try { FileInputStream fileInputStream = new FileInputStream(tempFile) { public void close() throws IOException { super.close(); maybeDeleteTempFile(this); } }; streamList.add(fileInputStream); return fileInputStream; } catch (FileNotFoundException e) { throw new IOException("Cached file was deleted, " + e.toString()); } } }
The maybeDeleteTempFile method:
private void maybeDeleteTempFile(Object stream) { streamList.remove(stream); if (!inmem && tempFile != null && streamList.isEmpty() && allowDeleteOfFile) { if (currentStream != null) { try { currentStream.close(); postClose(); } catch (Exception e) { //ignore } } tempFile.delete(); tempFile = null; currentStream = new LoadingByteArrayOutputStream(1024); inmem = true; } }