How to convert OutputStream to InputStream?

by

There seem to be many links and other such stuff, but no actual code using pipes. The advantage of using java.io.PipedInputStream and java.io.PipedOutputStream is that there is no additional consumption of memory. ByteArrayOutputStream.toByteArray() returns a copy of the original buffer, so that means that whatever you have in memory, you now have two copies of it. Then writing to an InputStream means you now have three copies of the data.

The code:

// take the copy of the stream and re-write it to an InputStream
PipedInputStream in = new PipedInputStream();
final PipedOutputStream out = new PipedOutputStream(in);
new Thread(new Runnable() {
    public void run () {
        try {
            // write the original OutputStream to the PipedOutputStream
            // note that in order for the below method to work, you need
            // to ensure that the data has finished writing to the
            // ByteArrayOutputStream
            originalByteArrayOutputStream.writeTo(out);
        }
        catch (IOException e) {
            // logging and exception handling should go here
        }
        finally {
            // close the PipedOutputStream here because we're done writing data
            // once this thread has completed its run
            if (out != null) {
                // close the PipedOutputStream cleanly
                out.close();
            }
        }   
    }
}).start();

This code assumes that the originalByteArrayOutputStream is a ByteArrayOutputStream as it is usually the only usable output stream, unless you’re writing to a file. I hope this helps! The great thing about this is that since it’s in a separate thread, it also is working in parallel, so whatever is consuming your input stream will be streaming out of your old output stream too. That is beneficial because the buffer can remain smaller and you’ll have less latency and less memory usage.

More Related Contents:

  1. How can an app use files inside the JAR for read and write?
  2. Connecting an input stream to an outputstream
  3. Can you explain the HttpURLConnection connection process?
  4. Java – How Can I Write My ArrayList to a file, and Read (load) that file to the original ArrayList?
  5. What is InputStream & Output Stream? Why and when do we use them?
  6. How do I convert an OutputStream to an InputStream?
  7. Convert InputStream to byte array in Java
  8. How can I read a text file in Android?
  9. How do I convert a String to an InputStream in Java?
  10. Should one call .close() on HttpServletResponse.getOutputStream()/.getWriter()?
  11. Read input stream twice
  12. How to clone an InputStream?
  13. How to identify end of InputStream in java
  14. Why does InputStream#read() return an int and not a byte?
  15. Is it necessary to close each nested OutputStream and Writer separately?
  16. How to read file from ZIP using InputStream?
  17. How to write data to two java.io.OutputStream objects at once?
  18. Reading streams from java Runtime.exec
  19. How to convert InputStream to virtual File
  20. Unable to read InputStream from Java Process (Runtime.getRuntime().exec() or ProcessBuilder)
  21. InputStream from a URL
  22. Getting InputStream with RestTemplate
  23. Determine the size of an InputStream
  24. Most efficient way to create InputStream from OutputStream
  25. Reading a binary input stream into a single byte array in Java
  26. How to Cache InputStream for Multiple Use
  27. Looping Error on Android Emulator
  28. ClassLoader getResourceAsStream returns null
  29. How to read pdf file and write it to outputStream [closed]
  30. What’s the fastest way to read from System.in in Java?

Leave a Comment