Download a file java example

To select a file from user file system, we need to use input element with type as file. We need to store file into some directory at server, we can have this directory hardcoded in program but for better flexibility, we will keep it configurable in deployment descriptor context params. Also we will add our upload file html page to the welcome file list. Since we need to read context parameter for file location and create a File object from it, we can write a ServletContextListener to do it when context is initialized.

We can set absolute directory location and File object as context attribute to be used by other servlets. Please check out Servlet 3 Upload File. For File upload, we will use Apache Commons FileUpload utility, for our project we are using version 1. FileItem provides useful method to get the file name, field name in form, size and content type details of the file that needs to be uploaded. To write file to a directory, all we need to do it create a File object and pass it as argument to FileItem write method.

Since the whole purpose of the servlet is to upload file, we will override init method to initialise the DiskFileItemFactory object instance of the servlet. We will use this object in the doPost method implementation to upload file to server directory.

Once the file gets uploaded successfully, we will send response to client with URL to download the file, since HTML links use GET method,we will append the parameter for file name in the URL and we can utilise the same servlet doGet method to implement file download process.

For implementing download file servlet, first we will open the InputStream for the file and use ServletContext. We will also need to set the response content length as length of the file.

Once we are done with setting response configuration, we can read file content from InputStream and write it to ServletOutputStream and the flush the output to client. Check out next article in the series about Servlet Exception Handling. Hey thank you for this tutorial. Hello Sir , Very Beatiful Example. I want to upload documents for particular user. John upload and views its documents 2. Marry upload and views its documents. This was a great tutorial. I had a few issues with the code at first, but was able to resolve.

As a suggestion it would be helpful to everyone to understand that your code is probably coding in a linux based system verses windows. If coding in windows, there maybe an issue with the AbsolutePath causing an issue with saving the file to the tempfile directory on the apache server.

If using apache as the web server. Also, the code is meant to upload the file once, any subsequent uploads will result in an exception because the file already exist. So, can force remove the existing file or simply add a! Thanks for the inputs. Nevermind this, I resolved this issue with my Intellij artifact setup.

The artifact must include the external libraries. Sorry for the trouble. Thanks for this tutorial,but when i upload the file it shows Exception in uploading file..

I had to change a few things to make this work. The biggest problem was that fileItem. I tried your code above, it works sometimes, sometimes meaning when I try downloading a 3. What do you think? I tried your code and it store the file in tmp directory. But i need to store in server.

How to save the file in url server. Just awesome topic! Its pretty easy to use. I think you can get a free trial if you ask for it. ClassNotFoundException: com. ExpressionFactoryImpl at org. Your code is working fine but I want to upload file with same name as well as same file type. Please help me in this matter. Thanks in advance. For Ex. File Directory created to be used for storing files java. Unknown Source at java. Unknown Source at org.

My aim is to upload an encrypted file to server. So what modification should i do in this basic code? I need to select a file, do aes encryption at client side and then after encryption upload encrypted file to server.

Again to retreive the file, do the decryption at client side. Exception in uploading file. In worder to get the correct file name i must use this FilenameUtils. Our code is built on top of Web Starter Application. We are using WebJars for Bootstrap and Jquery. At the core of this application will be our service class — FileSystemStorageService.

We will look at each of its functions in the rest of the article. This code is executed after the service class object is created. In this init method, we try to create the directory where we want to upload our files. This method will get a MultipartFile from Spring controller. The file name is then resolved relative to our upload directory and copied there. Above code, converts a file that we want to download into a Resource. This resource is later pushed to download via the controller.

We will use the copy inputStream, fileOS method to download a file into the local system. Check out our hands-on, practical guide to learning Git, with best-practices, industry-accepted standards, and included cheat sheet.

Stop Googling Git commands and actually learn it! The function returns the number of bytes copied. If the value of the variable i is -1, then it indicates that the contents of the file are over 2GB. When the returned value is -1, you can use the function copyLarge inputStream, fileOS in place of the copy inputstream, fileOS function to handle this load.

Both of these functions buffer the inputstream internally. 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.

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