Java download a file and save

The reason we use the BufferedInputStream class instead of the InputStream is its buffering ability that gives our code a performance boost. Before we dive deeper into the coding aspect let's take an overview of the classes and the individual functions we will be using in the process.

The java. URL class in Java is a built-in library that offers multiple methods to access and manipulate data on the internet. In this case, we will be using the openStream function of the URL class.

The method signature for the openStream function is:. The openStream function works on an object of the URL class. The URL class opens up a connection to the given URL and the openStream method returns an input stream which is used to read data from the connection. These classes are used for reading from a file and writing to it, respectively. The contents are read as bytes and copied to a file in the local directory using the FileOutputStream.

To lower the number of lines of code we can use the Files class available from Java 7. The Files class contains methods that read all the bytes at once and then copies it into another file. Here is how you can use it:. Java NIO is an alternative package to handle networking and input-output operations in Java. The main advantage that the Java NIO package offers is that it's non-blocking, and has channeling and buffering capabilities. When we use the Java IO library we work with streams that read data byte by byte.

However, the Java NIO package uses channels and buffers. The buffering and channeling capabilities allow the system to copy contents from a URL directly into the intended file without needing to save the bytes in application memory, which would be an intermediary step. The ability to work with channels boosts performance. The downloaded contents will be transferred to a file on the local system via the corresponding file channel.

After defining the file channel we will use the transferFrom method to copy the contents read from the readChannel object to the file destination using the writeChannel object. The transferFrom and transferTo methods are much more efficient than working with streams using a buffer. The transfer methods enable us to directly copy the contents of the file system cache to the file on the system.

Link; import com. TextField; import com. UI; import com. Thus, a new file path can be set. Improve this answer. Visruth Visruth 3, 31 31 silver badges 46 46 bronze badges. The file is created and stored on server disk. Anyone seen this? Make sure that the path is valid at the time of download. Can you check as :- First try with a sample text file containing more than 64KB of data and try to print the file contents in beforeDownload method itself, and verify it prints all of the contents.

Yes, it works on non-vm environments. The file is dynamically generated and stored on disk with Fileoutputstream and out. I use relative path and get error File not found: download? PDave it makes for me no sense to reference a local located file through a fileprovider like you did with "download?

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