The NIO Stream Storage project is a lightweight library to store streamed byte data using a combination of in memory and file storage. StreamStorage (which extends OutputStream) is used as the destination to write incoming bytes as they are available. It supplies an InputStream of the stored bytes when requested. Automatic resource management is available to ensure any underlying files are automatically be deleted once the InputStream is closed.

<dependency>
    <groupId>org.synchronoss.cloud</groupId>
    <artifactId>nio-stream-storage</artifactId>
    <version>1.0.0</version>
</dependency>

The implementation of StreamStorage, DeferredFileStreamStorage has two distinct states:

• The StreamStorage is ONLY writable and NOT readable.
• The StreamStorage is ONLY readable and NOT writable.

A new instance will always start in a write state, ready to accept bytes and any call to the getInputStream() will fail. Once all the data has been written, the close() method needs to be called to close the write channel and switch the DeferredFileStreamStorage to the read state. When the purgeFileAfterReadComplete flag is set to true the PurgeOnCloseFileInputStream ensures the temporary storage file is deleted if it exists. At that point the data can be read via getInputStream().

Instantiate a StreamStorage object either directly or via a configured Factory:

StreamStorageFactory streamStorageFactory = new DeferredFileStreamStorageFactory();
StreamStorage streamStorage = streamStorageFactory.create();

StreamStorage is an OutputStream so simply write bytes to it and close the stream once complete:

streamStorage.write(new byte[]{0x03, 0x4, 0x5});
streamStorage.write(new byte[]{0x01, 0x02});
streamStorage.close();

Retrieve an InputStream of the stored bytes:

InputStream inputStream = streamStorage.getInputStream();

Close the InputStream to cleanup the underlying file:

inputStream.close()

It is possible to configure an in-memory threshold before storing data on disk. If configured the data is flushed to disk only if that in-memory threshold is breached. This is provided as a potential optimisation to avoid unnecessary slow disk IO. It should be noted however that even without this option (when flushing directly to disk) there will likely be a Page Cache hit on the OS anyway, especially if the lifecycle of StreamStorage is relatively short-lived. So it may be worth bench-marking any use of this in-memory threshold.