Easy way to write contents of a Java InputStream to an OutputStream
I was surprised to find today that I couldn't track down any simple way to write the contents of an InputStream to an OutputStream in Java. Obviously, the byte buffer code isn't difficult to write, but I suspect I'm just missing something which would make my life easier (and the code clearer).
So, given an InputStream in and an OutputStream out , is there a simpler way to write the following?
byte[] buffer = new byte[1024];
int len = in.read(buffer);
while (len != -1) {
out.write(buffer, 0, len);
len = in.read(buffer);
}
As WMR mentioned, org.apache.commons.io.IOUtils from Apache has a method called copy(InputStream,OutputStream) which does exactly what you're looking for.
So, you have:
InputStream in;
OutputStream out;
IOUtils.copy(in,out);
in.close();
out.close();
...in your code.
Is there a reason you're avoiding IOUtils ?
If you are using Java 7, Files (in the standard library) is the best approach:
/* You can get Path from file also: file.toPath() */
Files.copy(InputStream in, Path target)
Files.copy(Path source, OutputStream out)
Edit: Of course it's just useful when you create one of InputStream or OutputStream from file. Use file.toPath() to get path from file.
To write into an existing file (eg one created with File.createTempFile() ), you'll need to pass the REPLACE_EXISTING copy option (otherwise FileAlreadyExistsException is thrown):
Files.copy(in, target, StandardCopyOption.REPLACE_EXISTING)
我认为这会起作用，但要确保测试它......微小的“改进”，但在可读性方面可能会有点成本。
byte[] buffer = new byte[1024];
int len;
while ((len = in.read(buffer)) != -1) {
out.write(buffer, 0, len);
}