This article provides code example of a sample Java web application that demonstrates how to implement file upload functionality based on Apache Common FileUpload API, servlet and JSP.
The application consists of the following source files:
Java runtime configuration:
<%@ page language="java" contentType="text/html; charset=UTF-8" 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 Demo</title> </head> <body> <center> <form method="post" action="uploadFile" enctype="multipart/form-data"> Select file to upload: <input type="file" name="uploadFile" /> <br/><br/> <input type="submit" value="Upload" /> </form> </center> </body> </html>
package net.codejava.upload; import java.io.File; import java.io.IOException; import java.io.PrintWriter; 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; /** * A Java servlet that handles file upload from client. * * @author www.codejava.net */ public class FileUploadServlet extends HttpServlet { private static final long serialVersionUID = 1L; // location to store file uploaded private static final String UPLOAD_DIRECTORY = "upload"; // upload settings private static final int MEMORY_THRESHOLD = 1024 * 1024 * 3; // 3MB private static final int MAX_FILE_SIZE = 1024 * 1024 * 40; // 40MB private static final int MAX_REQUEST_SIZE = 1024 * 1024 * 50; // 50MB /** * Upon receiving file upload submission, parses the request to read * upload data and saves the file on disk. */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // checks if the request actually contains upload file if (!ServletFileUpload.isMultipartContent(request)) { // if not, we stop here PrintWriter writer = response.getWriter(); writer.println("Error: Form must has enctype=multipart/form-data."); writer.flush(); return; } // configures upload settings DiskFileItemFactory factory = new DiskFileItemFactory(); // sets memory threshold - beyond which files are stored in disk factory.setSizeThreshold(MEMORY_THRESHOLD); // sets temporary location to store files factory.setRepository(new File(System.getProperty("java.io.tmpdir"))); ServletFileUpload upload = new ServletFileUpload(factory); // sets maximum size of upload file upload.setFileSizeMax(MAX_FILE_SIZE); // sets maximum size of request (include file + form data) upload.setSizeMax(MAX_REQUEST_SIZE); // constructs the directory path to store upload file // this path is relative to application's directory String uploadPath = getServletContext().getRealPath("") + File.separator + UPLOAD_DIRECTORY; // creates the directory if it does not exist File uploadDir = new File(uploadPath); if (!uploadDir.exists()) { uploadDir.mkdir(); } try { // parses the request's content to extract file data @SuppressWarnings("unchecked") List<FileItem> formItems = upload.parseRequest(request); if (formItems != null && formItems.size() > 0) { // iterates over form's fields for (FileItem item : formItems) { // processes only fields that are not form fields if (!item.isFormField()) { String fileName = new File(item.getName()).getName(); String filePath = uploadPath + File.separator + fileName; File storeFile = new File(filePath); // saves the file on disk item.write(storeFile); request.setAttribute("message", "Upload has been done successfully!"); } } } } catch (Exception ex) { request.setAttribute("message", "There was an error: " + ex.getMessage()); } // redirects client to message page getServletContext().getRequestDispatcher("/message.jsp").forward( request, response); } }
<%@ page language="java" contentType="text/html; charset=UTF-8" 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>Upload Result</title> </head> <body> <center> <h2>${message}</h2> </center> </body> </html>
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5"> <display-name>FileUploadServletExample</display-name> <servlet> <display-name>FileUploadServlet</display-name> <servlet-name>FileUploadServlet</servlet-name> <servlet-class>net.codejava.upload.FileUploadServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>FileUploadServlet</servlet-name> <url-pattern>/uploadFile</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>upload.jsp</welcome-file> </welcome-file-list> </web-app>
Download distribution and extract zip archive, then pick up jar file of the following libraries: