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POWhy doesn't more Java code use PipedInputStream / PipedOutputStream?
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copied!<p>I've discovered this idiom recently, and I am wondering if there is something I am missing. I've never seen it used. Nearly all Java code I've worked with in the wild favors slurping data into a string or buffer, rather than something like this example (using HttpClient and XML APIs for example):</p> <pre><code> final LSOutput output; // XML stuff initialized elsewhere final LSSerializer serializer; final Document doc; // ... PostMethod post; // HttpClient post request final PipedOutputStream source = new PipedOutputStream(); PipedInputStream sink = new PipedInputStream(source); // ... executor.execute(new Runnable() { public void run() { output.setByteStream(source); serializer.write(doc, output); try { source.close(); } catch (IOException e) { throw new RuntimeException(e); } }}); post.setRequestEntity(new InputStreamRequestEntity(sink)); int status = httpClient.executeMethod(post); </code></pre> <p>That code uses a Unix-piping style technique to prevent multiple copies of the XML data being kept in memory. It uses the HTTP Post output stream and the DOM Load/Save API to serialize an XML Document as the content of the HTTP request. As far as I can tell it minimizes the use of memory with very little extra code (just the few lines for <code>Runnable</code>, <code>PipedInputStream</code>, and <code>PipedOutputStream</code>).</p> <p>So, what's wrong with this idiom? If there's nothing wrong with this idiom, why haven't I seen it?</p> <p>EDIT: to clarify, <code>PipedInputStream</code> and <code>PipedOutputStream</code> replace the boilerplate buffer-by-buffer copy that shows up everywhere, and they also allow you to process incoming data concurrently with writing out the processed data. They don't use OS pipes.</p>

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