File Upload Example in Java using Servlet, JSP and Apache Commons FileUpload - Tutorial

Uploading Files to the server using Servlet and JSP is a common task in Java web applications. Before coding your Servlet or JSP to handle file upload requests, you need to know a little bit about File upload support in HTML and HTTP protocol. If you want your user to choose files from the file system and upload them to the server then you need to use <input type="file"/>. This will enable us to choose any file from the file system and upload to a server. 

The next thing is that the form method should be HTTP POST with enctype as multipart/form-data, which makes file data available in parts inside the request body. Now in order to read those file parts and create a File inside Servlet can be done by using ServletOutputStream.

Though, It's better to use Apache Commons FileUpload, an open-source library. Apache FileUpload handles all low details of parsing HTTP requests which conform to RFC 1867 or "Form-based File Upload in HTML” when you set form method post and content type as "multipart/form-data".

 

Apache Commons FileUpload - Important points:

1) DiskFileItemFactory is the default Factory class for FileItem. When Apache commons read multipart content and generate FileItem, this implementation keeps file content either in memory or in the disk as a temporary file, depending upon threshold size.

By default, DiskFileItemFactory has a threshold size of 10KB and generates temporary files in the temp directory, returned by System.getProperty("java.io.tmpdir"). 

Both of these values are configurable and it's best to configure these for production usage. You may get permission issues if the user account used for running the Server doesn't have sufficient permission to write files into the temp directory.

2) Choose threshold size carefully based upon memory usage, keeping large content in memory may result in java.lang.OutOfMemory, while having too small values may result in lot's of temporary files.

3) Apache commons file upload also provides FileCleaningTracker for deleting temporary files created by DiskFileItemFactory. FileCleaningTracker deletes temporary files as soon as the corresponding File instance is garbage collected. It accomplishes this by a cleaner thread which is created when FileCleaner is loaded. If you use this feature, then remember to terminate this Thread when your web application ends.

4) Keep configurable details e.g. upload directory, maximum file size, threshold size etc in config files and use reasonable default values in case they are not configured.

5) It's good to validate size, type, and other details of Files based upon your project requirement e.g. you may want to allow upload only images of a certain size and certain types e.g. JPEG, PNG, etc.

File Upload Example in Java Servlet and JSP

Here is the complete code for uploading files in Java web application using Servlet and JSP. This File Upload Example needs four files :

1. index.jsp which contains HTML content to set up a form, which allows the user to select and upload a file to the server.

2. FileUploader Servlet which handles file upload request and uses Apache FileUpload library to parse multipart form data

3. web.xml to configure servlet and JSP in Java web application.

4. result.jsp for showing the result of the file upload operation.

FileUploadHandler.java

import java.io.File;

import java.io.IOException;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;

import org.apache.commons.fileupload.disk.DiskFileItemFactory;

import org.apache.commons.fileupload.servlet.ServletFileUpload;

/**

 * Servlet to handle File upload request from Client

 * @author Javin Paul

 */

public class FileUploadHandler extends HttpServlet {

    private final String UPLOAD_DIRECTORY = "C:/uploads";

  

    @Override

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

      

        //process only if its multipart content

        if(ServletFileUpload.isMultipartContent(request)){

            try {

                List<FileItem> multiparts = new ServletFileUpload(

                                         new DiskFileItemFactory()).parseRequest(request);

              

                for(FileItem item : multiparts){

                    if(!item.isFormField()){

                        String name = new File(item.getName()).getName();

                        item.write( new File(UPLOAD_DIRECTORY + File.separator + name));

                    }

                }

           

               //File uploaded successfully

               request.setAttribute("message", "File Uploaded Successfully");

            } catch (Exception ex) {

               request.setAttribute("message", "File Upload Failed due to " + ex);

            }          

         

        }else{

            request.setAttribute("message",

                                 "Sorry this Servlet only handles file upload request");

        }

    

        request.getRequestDispatcher("/result.jsp").forward(request, response);

     

    }

  

}

index.jsp

<%@page contentType="text/html" pageEncoding="UTF-8"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"

    "http://www.w3.org/TR/html4/loose.dtd">

<html>

    <head>

        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

        <title>File Upload Example in JSP and Servlet - Java web application</title>

    </head>

 

    <body> 

        <div>

            <h3> Choose File to Upload in Server </h3>

            <form action="upload" method="post" enctype="multipart/form-data">

                <input type="file" name="file" />

                <input type="submit" value="upload" />

            </form>          

        </div>

      

    </body>

</html>

result.jsp

<%@page contentType="text/html" pageEncoding="UTF-8"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"

    "http://www.w3.org/TR/html4/loose.dtd">

<html>

    <head>

        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

        <title>File Upload Example in JSP and Servlet - Java web application</title>

    </head>

 

    <body> 

        <div id="result">

            <h3>${requestScope["message"]}</h3>

        </div>

      

    </body>

</html>

web.xml

<?xml version="1.0" encoding="UTF-8"?>

<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

   <servlet>

        <servlet-name>FileUploadHandler</servlet-name>

        <servlet-class>FileUploadHandler</servlet-class>

    </servlet>

    <servlet-mapping>

        <servlet-name>FileUploadHandler</servlet-name>

        <url-pattern>/upload</url-pattern>

    </servlet-mapping>

  

  

    <session-config>

        <session-timeout>

            30

        </session-timeout>

    </session-config>

    <welcome-file-list>

        <welcome-file>index.jsp</welcome-file>

    </welcome-file-list>

</web-app>

In summary, just keep three things in mind while uploading files using Java web application

1) Use HTML form input type as File to browse files to upload

2) Use form method as post and enctype as multipart/form-data

3) Use Apache commons FileUpload in Servlet to handle HTTP requests with multipart data.

Dependency

In order to compile and run this Java web application in any web server e.g. Tomcat, you need to include following dependency JAR in the WEB-INF lib folder.

commons-fileupload-1.2.2.jar

commons-io-2.4.jar

If you are using Maven then you can also use following dependencies :

<dependency>

     <groupId>commons-fileupload</groupId>

     <artifactId>commons-fileupload</artifactId>

     <version>1.2.2</version>

</dependency>

<dependency>

     <groupId>commons-io</groupId>

     <artifactId>commons-io</artifactId>

     <version>2.4</version>

</dependency>

That's all on How to Upload Files using Servlet and JSP in Java web application. This File Upload example can be written using JSP, Filter or Servlet because all three are request’s entry points in Java web application. I have used Servlet for handling File upload request for simplicity. By the way from Servlet 3.0 API, Servlet is supporting multipart form data and you can use the getPart() method of HttpServletRequest to handle file upload.