Convert InputStream to byte array in Java
Convert InputStream to byte array in Java
Accepted Answer
You can use Apache Commons IO to handle this and similar tasks.
The IOUtils type has a static method to read an InputStream and return a byte[].
InputStream is;
byte[] bytes = IOUtils.toByteArray(is);
Internally this creates a ByteArrayOutputStream and copies the bytes to the output, then calls toByteArray(). It handles large files by copying the bytes in blocks of 4KiB.
Popular Answer
You need to read each byte from your InputStream and write it to a ByteArrayOutputStream.
You can then retrieve the underlying byte array by calling toByteArray():
InputStream is = ...
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
int nRead;
byte[] data = new byte[16384];
while ((nRead = is.read(data, 0, data.length)) != -1) {
buffer.write(data, 0, nRead);
}
return buffer.toByteArray();
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Finally, after twenty years, there’s a simple solution without the need for a 3rd party library, thanks to Java 9:
InputStream is;
…
byte[] array = is.readAllBytes();
Note also the convenience methods readNBytes(byte[] b, int off, int len) and transferTo(OutputStream) addressing recurring needs.
Use vanilla Java's DataInputStream and its readFully Method (exists since at least Java 1.4):
...
byte[] bytes = new byte[(int) file.length()];
DataInputStream dis = new DataInputStream(new FileInputStream(file));
dis.readFully(bytes);
...
There are some other flavors of this method, but I use this all the time for this use case.
If you happen to use google guava, it'll be as simple as :
byte[] bytes = ByteStreams.toByteArray(inputStream);
As always, also Spring framework (spring-core since 3.2.2) has something for you: StreamUtils.copyToByteArray()
public static byte[] getBytesFromInputStream(InputStream is) throws IOException {
ByteArrayOutputStream os = new ByteArrayOutputStream();
byte[] buffer = new byte[0xFFFF];
for (int len = is.read(buffer); len != -1; len = is.read(buffer)) {
os.write(buffer, 0, len);
}
return os.toByteArray();
}