Java download file from url to directory

This code allows you to download a file in Java according to its URL and save it at the specific destination. I know there are several methods for grabbing and reading online files URLs line-by-line, but is there a way to just download and save the file using Java? Using transferFrom is potentially much more efficient than a simple loop that reads from the source channel and writes to this channel. Many operating systems can transfer bytes directly from the source channel into the filesystem cache without actually copying them.

Note : The third parameter in transferFrom is the maximum number of bytes to transfer. Downloading a file requires you to read it, either way you will have to go through the file in some way. Instead of line by line, you can just read it by bytes from the stream:. It's an old question but here is a concise, readable, JDK-only solution with properly closed resources:. The internal buffer means we do not have to use the BufferedInputStream class to enhance our code performance and helps us avoid writing boilerplate code.

Another library managed by the Apache organization is the HttpComponents package. This library uses the request-response mechanism to download the file from a given URL. The first step to downloading a file is to create an HTTP client object that would issue the request to the server. For this, we will be using the CloseableHttpClient class.

The code snippet that creates a new HTTP client is as follows:. We then need to create an HttpGet or HttpPost object to send the request to the server. The request is created by the following line of code:. The execute request function is applied to the client object and returns with a response from the server. Once the request is sent to the server we need a response object to receive the data sent from the server.

To catch the response from the server we use the HttpResponse class object. The data sent by the server in the form of a message is obtained through the getEntity function. You can also obtain the response code sent by the server through the response object and use it to your specific need. The data to be downloaded is encapsulated within the entity object and can be extracted using the getContent function.

The getContent function returns an InputStream object that can be further used with a BufferedInputStreamReader to enhance performance.

Now all you need to do is read from the stream byte by byte and write the contents into a file using the FileOutputStream class. The last thing required to be done is closing all the open resources in order to ensure that the system resources are not overutilized and that there are no memory leaks.

Full working code to download a file when you are behind a proxy. I am not sure how to download this since it has the MD5 and expiry time as parameters, and so wget only downloads a web page, not this ISO. On linux and alike systems, this makes it a background process. Solution it to enclose url in double quoutes ' so that its treated as one argument. If you are just trying to get a reasonable filename the complex URL, you can use the output-document option. As noted previously, be sure none of the special characters in the URL are getting interpreted by the command parser.

ISO :. So if you ask me, the second method works best for most average use. Also notice the -L flag being used in both commands; that commands tells Curl to follow any redirection links that a file download URL might have since a lot of times files on download services redirect a few times before landing at the destination payload file.

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