在非阻塞模式下从InputStream读取所有字节

Question

Trying to find solution to read all bytes from InputStream in non blocking mode. Section inputStream.read() in function below blocks forever when no data are available.

private static String extract(InputStream inputStream) throws IOException { 
    ByteArrayOutputStream baos = new ByteArrayOutputStream();               
    byte[] buffer = new byte[1024];
    int read = 0;
    while ((read = inputStream.read(buffer, 0, buffer.length)) != -1) {
        baos.write(buffer, 0, read);
    }       
    baos.flush();       
    return  new String(baos.toByteArray(), "UTF-8");
}

How to read all bytes without blocking?

Answer 1

I assume you want a timeout for reading.

For an URLConnection (should the InputStream stem from that) you can set miscellaneous timeouts, and check the optimal blocksize (that from the sender).

For Sockets the same functionality exists.

A timeout one can make oneself using a thread: this I found on SO .

But also Future seems appropriate:

ExecutorService service = Executors.newFixedThreadPool(2); // Or whatever.
// Callable<String> callable = () -> extract(inputStream);
Future<String> future = service.submit(() -> extract(inputStream));
try {
    String s = future.get(3, TimeUnit.SECONDS);
} catch (Exception e){
    e.printStackTrace();
    future.cancel(true);
    inputStream.close();
}

Answer 2

您可以使用InputStream.available()方法在读取之前测试多少字节可用。