The FileReader interface has pretty good browser support and supports reading blob data as follows as at the time of this writing :. Here is what a typical object URL looks like:. The URL. Here is what it looks like:.
It is important to note that, this method will always return a new object URL each time it is called, even if it is called with the same blob object. Whenever an object URL is created, it stays around for the lifetime of the document on which it was created. Usually, the browser will release all object URLs when the document is being unloaded. However, it is important that you release object URLs whenever they are no longer needed in order to improve performance and minimize memory usage.
It takes the object URL to be released as its argument. For example:. We have also seen how we can programmatically extract or generate content in the browser using Web APIs. In this section, we will examine how we can download programmatically generate content in the browser, leveraging all we have learned from the beginning of the article and what we already know about blobs and object URLs.
The logic of our helper function can be broken down as follows:. Here is what an implementation of this helper function will look like:. That was a pretty straightforward implementation of the download link helper function. Notice that the helper triggers a one-off automatic download of the blob content whenever it is called.
Also notice that the helper function takes a filename as its second argument, which is very useful for setting the default filename for the downloaded file. Now that we have our download helper function in place, we can revisit our previous examples and modify them to trigger a download for the generated content. 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. Free certificates of completion Focused on data science skills Flexible learning timetable.
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Related Code Examples JavaScript. Precision of JavaScript Number. Constructors in JavaScript String Conversion. Like Article. Download File Using. Download this file. For Downloading, Click. Recommended Articles. Article Contributed By :. I do not get the file. I only get the file url from the server as part of a json object — user Rock Rock 19 5 5 bronze badges.
I do not want it to open in browser. I want to download it. Whats the format of file, i mean file extension. If you want to downlaod even pdf and image then set proper content type at server side — Rock. It could be any of the following. Show 1 more comment. The file url that I get is an absolute file url, not the actual file itself. Also, I am not aware of java. If you could help me using javascript, I'd really appreciate that!
Javascript it can only work in the way what i explained above.
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