Here are just a few ways of how you can accomplish the task:. The most easily available and a basic package available for downloading a file from internet using Java code is the Java IO package. Here we will be using the BufferedInputStream and the URL classes to open and read a file on a given address to a file on our local system.
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.
Thus direct channeling restricts the number of context switches required and enhances the overall code performance. Now, in the following sections, we will be looking at ways to download files from a URL using third-party libraries instead of core Java functionality components. Now you may be thinking why would we use this when Java has its own set of libraries to handle IO operations. However, Apache Commons IO overcomes the problem of code rewriting and helps avoid writing boilerplate code.
In order to start using the Apache Commons IO library, you will need to download the jar files from the official website. When you are done downloading the jar files, you need to add them to use them. If you are using an Integrated Development Environment IDE such as Eclipse , you will need to add the files to the build path of your project. There is only a single line of code required to download a file, which looks like:.
The connection and read timeouts convey the permissible time for which either the connection may stay idle or reading from the URL may stop. More info about AsyncTask on Android documentation. Run these codes in thread or AsyncTask. Here is the code help you to download file from server at the same time you can see the progress of downloading on your status bar. Here i create an asynchronous task to download file. Note: If you want code with import package then Click Here.
Now Step 2: You need to call above ayncronous task on your click event. To call AsyncTask use below code:. Note: Here You can see filename variable in file parameter. This is the name which i use to save my downloaded file in local device. When you click on download button, first you have to create local storage path where you want to save it, we should put download file functionality into ExecutorService that is used instead of AsyncTask because AsyncTask is deprecated. Starting from api level 11 or Honeycomb doing network operations on main thread is forbidden.
Use thread or asynctask. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Android - How to download a file from a webserver Ask Question.
Asked 8 years, 7 months ago. Active 2 months ago. Viewed k times. DataInputStream; import java. File; import java. FileOutputStream; import java. IOException; import java. InputStream; import java. MalformedURLException; import java. URL; import android. Activity; import android. Bundle; import android. Environment; import android. Log; import android. BufferedInputStream; import java. OutputStream; import java. URL; import java. URLConnection; import android.
Dialog; import android. ProgressDialog; import android. AsyncTask; import android. Please wait Iam4fun Iam4fun 1, 3 3 gold badges 13 13 silver badges 18 18 bronze badges. Do NOT perform network related operation on main thread. Create a separate thread for downloading the file.
You do not need to call conection. Add a comment. Active Oldest Votes. Brokkoli 71 8 8 bronze badges. Nirav Ranpara Nirav Ranpara This example has a problem. When the codes run at line where getContentLength a request will be sent with url and then later again at line of url.
Show 1 more comment. This is the same realization as defined in InputStream. N connection. Vlad Vlad 6, 2 2 gold badges 45 45 silver badges 42 42 bronze badges. One more time, kotlin makes simple what should be simple. JordanH it's depend on how you are using this function — Vlad. Request uri ; request. Awsom3D Awsom3D 6 6 silver badges 21 21 bronze badges.
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