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If you have java.io.InputStream object, how should you process that object and produce a String?

Suppose I have an InputStream that contains text data, and I want to convert this to a String (for example, so I can write the contents of the stream to a log file).

What is the easiest way to take the InputStream and convert it to a String?

public String convertStreamToString(InputStream is) { 
    // ???
}

2Answer


0

A nice way to do this is using Apache commons IOUtils to copy the InputStream into a StringWriter... something like

StringWriter writer = new StringWriter();
IOUtils.copy(inputStream, writer, encoding);
String theString = writer.toString();

or even

// NB: does not close inputStream, you can use IOUtils.closeQuietly for that
String theString = IOUtils.toString(inputStream, encoding); 

Alternatively, you could use ByteArrayOutputStream if you don't want to mix your Streams and Writers

  • answered 3 years ago
  • Gul Hafiz

0

Here's a way using only standard Java library (note that the stream is not closed, YMMV).

static String convertStreamToString(java.io.InputStream is) {
    java.util.Scanner s = new java.util.Scanner(is).useDelimiter("\\A");
    return s.hasNext() ? s.next() : "";
}

I learned this trick from "Stupid Scanner tricks" article. The reason it works is because Scanneriterates over tokens in the stream, and in this case we separate tokens using "beginning of the input boundary" (\A) thus giving us only one token for the entire contents of the stream.

Note, if you need to be specific about the input stream's encoding, you can provide the second argument to Scanner constructor that indicates what charset to use (e.g. "UTF-8").

  • answered 3 years ago
  • Gul Hafiz

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