对于我的一个项目FileSystem
,我在 Box API Java SDK(新的)上实现了 Java 7 。
但是,对于下载文件,当您想要内容流时,它只提供OutputStream
作为参数的方法;具体来说,我目前正在使用这个。
但这不适用于 JDK API。我需要能够实现FileSystemProvider#newInputStream()
......因此我选择使用Pipe{Input,Output}Stream
.
此外,由于 Box SDK API 方法是同步的(在这里并不重要),我将它们包装在Future
. 我的代码如下(为简洁起见省略了导入):
@ParametersAreNonnullByDefault
public final class BoxFileInputStream
extends InputStream
{
private final Future<Void> future;
private final PipedInputStream in;
public BoxFileInputStream(final ExecutorService executor,
final BoxFile file)
{
in = new PipedInputStream(16384);
future = executor.submit(new Callable<Void>()
{
@Override
public Void call()
throws IOException
{
try {
file.download(new PipedOutputStream(in));
return null;
} catch (BoxAPIException e) {
throw BoxIOException.wrap(e);
}
}
});
}
@Override
public int read()
throws IOException
{
try {
return in.read();
} catch (IOException e) {
future.cancel(true);
throw new BoxIOException("download failure", e);
}
}
@Override
public int read(final byte[] b)
throws IOException
{
try {
return in.read(b);
} catch (IOException e) {
future.cancel(true);
throw new BoxIOException("download failure", e);
}
}
@Override
public int read(final byte[] b, final int off, final int len)
throws IOException
{
try {
return in.read(b, off, len);
} catch (IOException e) {
future.cancel(true);
throw new BoxIOException("download failure", e);
}
}
@Override
public long skip(final long n)
throws IOException
{
try {
return in.skip(n);
} catch (IOException e) {
future.cancel(true);
throw new BoxIOException("download failure", e);
}
}
@Override
public int available()
throws IOException
{
try {
return in.available();
} catch (IOException e) {
future.cancel(true);
throw new BoxIOException("download failure", e);
}
}
@Override
public void close()
throws IOException
{
IOException streamException = null;
IOException futureException = null;
try {
in.close();
} catch (IOException e) {
streamException = e;
}
try {
future.get(5L, TimeUnit.SECONDS);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
futureException = new BoxIOException("donwload interrupted", e);
} catch (ExecutionException e) {
futureException = new BoxIOException("download failure",
e.getCause());
} catch (CancellationException e) {
futureException = new BoxIOException("download cancelled", e);
} catch (TimeoutException e) {
futureException = new BoxIOException("download timeout", e);
}
if (futureException != null) {
if (streamException != null)
futureException.addSuppressed(streamException);
throw futureException;
}
if (streamException != null)
throw streamException;
}
@Override
public synchronized void mark(final int readlimit)
{
in.mark(readlimit);
}
@Override
public synchronized void reset()
throws IOException
{
try {
in.reset();
} catch (IOException e) {
future.cancel(true);
throw new BoxIOException("download failure", e);
}
}
@Override
public boolean markSupported()
{
return in.markSupported();
}
}
该代码始终失败并显示以下堆栈跟踪(即在int read(byte[])
:
Exception in thread "main" com.github.fge.filesystem.box.exceptions.BoxIOException: download failure
at com.github.fge.filesystem.box.io.BoxFileInputStream.read(BoxFileInputStream.java:81)
at java.nio.file.Files.copy(Files.java:2735)
at java.nio.file.Files.copy(Files.java:2854)
at java.nio.file.CopyMoveHelper.copyToForeignTarget(CopyMoveHelper.java:126)
at java.nio.file.Files.copy(Files.java:1230)
at Main.main(Main.java:37)
[ IDEA specific stack trace elements follow -- irrelevant]
Caused by: java.io.IOException: Pipe broken
at java.io.PipedInputStream.read(PipedInputStream.java:322)
at java.io.PipedInputStream.read(PipedInputStream.java:378)
at java.io.InputStream.read(InputStream.java:101)
at com.github.fge.filesystem.box.io.BoxFileInputStream.read(BoxFileInputStream.java:78)
... 10 more
但是当它失败时,下载已经完成......
好的,问题是,我可以获取文件大小并绕过它,但如果可能的话,我宁愿不这样做;如何修改此代码以避免 EPIPE?