How to retrieve uploaded image and save to a file with JSP?

Question

Sorry but I'm totally new to jsp.

How to retrieve uploaded image and save to a file with jsp?

Answer 1

It's a bit complicated when using pure jsp/servlets, that's why Apache created commons-fileupload.

In short:

1. define <input type="file" />
2. set <form method="post" enctype="multipart/form-data">

3. In the servlet/jsp where you handle the form:

   // Create a factory for disk-based file items
   FileItemFactory factory = new DiskFileItemFactory();
   
   
   // Create a new file upload handler
   ServletFileUpload upload = new ServletFileUpload(factory);
   
   
   // Parse the request
   List /* FileItem */ items = upload.parseRequest(request);
   

And then you proceed with java.io to write your file (I assume you know how to do this)

Answer 2

1. Create a web project.

2. Create a JSP file with at least the following content:

   <form action="upload" method="post" enctype="multipart/form-data">
       <input type="file" name="file">
       <input type="submit">
   </form>
   

3. Go to Apache Commons FileUpload homepage, read both the User Guide and Frequently Asked Questions sections.

4. Download the binaries of the following libraries:

   • commons-fileupload
   • commons-io

5. Unpack the zips and place the JAR files in the /WEB-INF/lib of your web project.

6. Create a Servlet class with at least the following content:

   public class UploadServlet extends HttpServlet {
       protected void doPost(HttpServletRequest request, HttpServletResposne response) throws ServletException, IOException {
           List<FileItem> items = null;
           try {
               items = new ServletFileUpload(new DiskFileItemFactory()).parseRequest(request);
           } catch (FileUploadException e) {
               throw new ServletException("Cannot parse multipart request.", e);
           }
           for (FileItem item : items) {
               if (item.isFormField()) {
                   // Process regular form fields here the same way as request.getParameter().
                   // You can get parameter name by item.getFieldName();
                   // You can get parameter value by item.getString();
               } else {
                   // Process uploaded fields here.
                   String filename = FilenameUtils.getName(item.getName()); // Get filename.
                   File file = new File("/path/to/uploads", filename); // Define destination file.
                   item.write(file); // Write to destination file.
               }
           }
           // Show result page.
           request.getRequestDispatcher("result.jsp").forward(request, response);
       }
   }
   

7. Map the servlet in web.xml as follows:

   <servlet>
       <servlet-name>upload</servlet-name>
       <servlet-class>mypackage.UploadServlet</servlet-class>
   </servlet>
   <servlet-mapping>
       <servlet-name>upload</servlet-name>
       <url-pattern>/upload</url-pattern>
   </servlet-mapping>
   

That should be it. When you submit the form in the JSP, it will invoke the action /upload which matches the <url-pattern> of the servlet and then the servlet will do its task in the doPost() method. At end it's all fairly simple. Hope this helps.