There is an online file (such as http://www.example.com/information.asp
) I need to grab and save to a directory. I know there are several methods for grabbing a
Use apache commons-io, just one line code:
FileUtils.copyURLToFile(URL, File)
When using Java 7+
use the following method to download a file from the Internet and save it to some directory:
private static Path download(String sourceURL, String targetDirectory) throws IOException
{
URL url = new URL(sourceURL);
String fileName = sourceURL.substring(sourceURL.lastIndexOf('/') + 1, sourceURL.length());
Path targetPath = new File(targetDirectory + File.separator + fileName).toPath();
Files.copy(url.openStream(), targetPath, StandardCopyOption.REPLACE_EXISTING);
return targetPath;
}
Documentation here.
There is method U.fetch(url) in underscore-java library.
pom.xml:
<groupId>com.github.javadev</groupId>
<artifactId>underscore</artifactId>
<version>1.45</version>
Code example:
import com.github.underscore.lodash.U;
public class Download {
public static void main(String ... args) {
String text = U.fetch("https://stackoverflow.com/questions"
+ "/921262/how-to-download-and-save-a-file-from-internet-using-java").text();
}
}
Simpler nio usage:
URL website = new URL("http://www.website.com/information.asp");
try (InputStream in = website.openStream()) {
Files.copy(in, target, StandardCopyOption.REPLACE_EXISTING);
}
There are many elegant and efficient answers here. But the conciseness can make us lose some useful information. In particular, one often does not want to consider a connection error an Exception, and one might want to treat differently some kind of network-related errors - for example, to decide if we should retry the download.
Here's a method that does not throw Exceptions for network errors (only for truly exceptional problems, as malformed url or problems writing to the file)
/**
* Downloads from a (http/https) URL and saves to a file.
* Does not consider a connection error an Exception. Instead it returns:
*
* 0=ok
* 1=connection interrupted, timeout (but something was read)
* 2=not found (FileNotFoundException) (404)
* 3=server error (500...)
* 4=could not connect: connection timeout (no internet?) java.net.SocketTimeoutException
* 5=could not connect: (server down?) java.net.ConnectException
* 6=could not resolve host (bad host, or no internet - no dns)
*
* @param file File to write. Parent directory will be created if necessary
* @param url http/https url to connect
* @param secsConnectTimeout Seconds to wait for connection establishment
* @param secsReadTimeout Read timeout in seconds - trasmission will abort if it freezes more than this
* @return See above
* @throws IOException Only if URL is malformed or if could not create the file
*/
public static int saveUrl(final Path file, final URL url,
int secsConnectTimeout, int secsReadTimeout) throws IOException {
Files.createDirectories(file.getParent()); // make sure parent dir exists , this can throw exception
URLConnection conn = url.openConnection(); // can throw exception if bad url
if( secsConnectTimeout > 0 ) conn.setConnectTimeout(secsConnectTimeout * 1000);
if( secsReadTimeout > 0 ) conn.setReadTimeout(secsReadTimeout * 1000);
int ret = 0;
boolean somethingRead = false;
try (InputStream is = conn.getInputStream()) {
try (BufferedInputStream in = new BufferedInputStream(is); OutputStream fout = Files
.newOutputStream(file)) {
final byte data[] = new byte[8192];
int count;
while((count = in.read(data)) > 0) {
somethingRead = true;
fout.write(data, 0, count);
}
}
} catch(java.io.IOException e) {
int httpcode = 999;
try {
httpcode = ((HttpURLConnection) conn).getResponseCode();
} catch(Exception ee) {}
if( somethingRead && e instanceof java.net.SocketTimeoutException ) ret = 1;
else if( e instanceof FileNotFoundException && httpcode >= 400 && httpcode < 500 ) ret = 2;
else if( httpcode >= 400 && httpcode < 600 ) ret = 3;
else if( e instanceof java.net.SocketTimeoutException ) ret = 4;
else if( e instanceof java.net.ConnectException ) ret = 5;
else if( e instanceof java.net.UnknownHostException ) ret = 6;
else throw e;
}
return ret;
}
It's possible to download the file with with Apache's HttpComponents
instead of Commons-IO
. This code allows you to download a file in Java according to its URL and save it at the specific destination.
public static boolean saveFile(URL fileURL, String fileSavePath) {
boolean isSucceed = true;
CloseableHttpClient httpClient = HttpClients.createDefault();
HttpGet httpGet = new HttpGet(fileURL.toString());
httpGet.addHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.3; WOW64; rv:34.0) Gecko/20100101 Firefox/34.0");
httpGet.addHeader("Referer", "https://www.google.com");
try {
CloseableHttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity fileEntity = httpResponse.getEntity();
if (fileEntity != null) {
FileUtils.copyInputStreamToFile(fileEntity.getContent(), new File(fileSavePath));
}
} catch (IOException e) {
isSucceed = false;
}
httpGet.releaseConnection();
return isSucceed;
}
In contrast to the single line of code:
FileUtils.copyURLToFile(fileURL, new File(fileSavePath),
URLS_FETCH_TIMEOUT, URLS_FETCH_TIMEOUT);
this code will give you more control over a process and let you specify not only time outs but User-Agent
and Referer
values, which are critical for many web-sites.