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) {
// ???
}
If you want to do it simply and reliably, I suggest using the Apache Jakarta Commons IO library IOUtils.toString(java.io.InputStream, java.lang.String) method.
This is my version,
public static String readString(InputStream inputStream) throws IOException {
ByteArrayOutputStream into = new ByteArrayOutputStream();
byte[] buf = new byte[4096];
for (int n; 0 < (n = inputStream.read(buf));) {
into.write(buf, 0, n);
}
into.close();
return new String(into.toByteArray(), "UTF-8"); // Or whatever encoding
}
String text = new Scanner(inputStream).useDelimiter("\\A").next();
The only tricky is to remember the regex
\A, which matches the beginning of input. This effectively tellsScannerto tokenize the entire stream, from beginning to (illogical) next beginning...
- from the Oracle Blog
Since Java 9 InputStream.readAllBytes() even shorter:
String toString(InputStream inputStream) throws IOException {
return new String(inputStream.readAllBytes(), StandardCharsets.UTF_8); // Or whatever encoding
}
Note: InputStream is not closed in this example.
You can use a BufferedReader to read the stream into a StringBuilder in a loop, and then get the full contents from the StringBuilder:
public String convertStreamToString(InputStream is) {
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
StringBuilder sb = new StringBuilder();
String line = null;
try {
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return sb.toString();
}
Full disclosure: This is a solution I found on KodeJava.org. I am posting it here for comments and critique.
A nice way to do this is using Apache commons IOUtils
IOUtils.toString(inputStream, string);
