Read text from InputStream

Question

If I start with a java.io.InputStream, what's the easiest way to read the entire stream out into a String (assuming utf-8)?

This should be pretty easy but I'm mostly a C# person and google is failing me on this. Thanks.

Answer 1

Reading/writing from streams is remarkably painful in Java.

public static String getStreamContents(InputStream stream) throws IOException {

    StringBuilder content = new StringBuilder()

    Reader reader = new BufferedReader(new InputStreamReader(stream, "UTF-8"))
    String lineSeparator = System.getProperty("line.separator");

    try {
        String line
        while ((line = reader.readLine()) != null) {
            content.append(line + lineSeparator)
        }
        return content.toString()

    } finally {
        reader.close()
    }

}

Answer 2

Depending on what licenses you are comfortable with, it's a one liner with Jakarta-Commons IO library.

Answer 3

Do specify the character encoding. Do not waste code, introduce bugs, and slow execution with a BufferedReader.

Here is an example. You could parameterize it with a buffer size, encoding, etc.

static String readString(InputStream is) throws IOException {
  char[] buf = new char[2048];
  Reader r = new InputStreamReader(is, "UTF-8");
  StringBuilder s = new StringBuilder();
  while (true) {
    int n = r.read(buf);
    if (n < 0)
      break;
    s.append(buf, 0, n);
  }
  return s.toString();
}

Answer 4

Using Commons-IO is likely to be the best option. For your interest, another approach is to copy all the bytes and then convert it into a String.

public static String readText(InputStream is, String charset) throws IOException {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    byte[] bytes = new byte[4096];
    for(int len;(len = is.read(bytes))>0;)
        baos.write(bytes, 0, len);
    return new String(baos.toByteArray(), charset);
}