java - Guava equivalent for IOUtils.toString(InputStream)

Question

Apache Commons IO has a nice convenience method IOUtils.toString() to read an InputStream to a String.

Since I am trying to move away from Apache Commons and to Guava: is there an equivalent in Guava? I looked at all classes in the com.google.common.io package and I couldn't find anything nearly as simple.

Edit: I understand and appreciate the issues with charsets. It just so happens that I know that all my sources are in ASCII (yes, ASCII, not ANSI etc.), so in this case, encoding is not an issue for me.

Answer 1

You stated in your comment on Calum's answer that you were going to use

CharStreams.toString(new InputStreamReader(supplier.get(), Charsets.UTF_8))

This code is problematic because the overload CharStreams.toString(Readable) states:

Does not close the Readable.

This means that your InputStreamReader, and by extension the InputStream returned by supplier.get(), will not be closed after this code completes.

If, on the other hand, you take advantage of the fact that you appear to already have an InputSupplier<InputStream> and used the overload CharStreams.toString(InputSupplier<R extends Readable & Closeable>), the toString method will handle both the creation and closing of the Reader for you.

This is exactly what Jon Skeet suggested, except that there isn't actually any overload of CharStreams.newReaderSupplier that takes an InputStream as input... you have to give it an InputSupplier:

InputSupplier<? extends InputStream> supplier = ...
InputSupplier<InputStreamReader> readerSupplier = 
    CharStreams.newReaderSupplier(supplier, Charsets.UTF_8);

// InputStream and Reader are both created and closed in this single call
String text = CharStreams.toString(readerSupplier);

The point of InputSupplier is to make your life easier by allowing Guava to handle the parts that require an ugly try-finally block to ensure that resources are closed properly.

Edit: Personally, I find the following (which is how I'd actually write it, was just breaking down the steps in the code above)

String text = CharStreams.toString(
    CharStreams.newReaderSupplier(supplier, Charsets.UTF_8));

to be far less verbose than this:

String text;
InputStreamReader reader = new InputStreamReader(supplier.get(), 
    Charsets.UTF_8);
boolean threw = true;
try {
  text = CharStreams.toString(reader);
  threw = false;
}
finally {
  Closeables.close(reader, threw);
}

Which is more or less what you'd have to write to handle this properly yourself.

---

Edit: Feb. 2014

InputSupplier and OutputSupplier and the methods that use them have been deprecated in Guava 16.0. Their replacements are ByteSource, CharSource, ByteSink and CharSink. Given a ByteSource, you can now get its contents as a String like this:

ByteSource source = ...
String text = source.asCharSource(Charsets.UTF_8).read();