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Thursday, 1 September 2016

Creating a File Upload Form:

Creating a File Upload Form:

The following HTM code below creates an uploader form. Following are the important points to be noted down:
  • The form method attribute should be set to POST method and GET method can not be used.
  • The form enctype attribute should be set to multipart/form-data.
  • The form action attribute should be set to a JSP file which would handle file uploading at backend server. Following example is usinguploadFile.jsp program file to upload file.
  • To upload a single file you should use a single <input .../> tag with attribute type="file". To allow multiple files uploading, include more than one input tags with different values for the name attribute. The browser associates a Browse button with each of them.
  • <html>
    <head>
    <title>File Uploading Form</title>
    </head>
    <body>
    <h3>File Upload:</h3>
    Select a file to upload: <br />
    <form action="UploadServlet" method="post"
                            enctype="multipart/form-data">
    <input type="file" name="file" size="50" />
    <br />
    <input type="submit" value="Upload File" />
    </form>
    </body>
    </html>
This will display following result which would allow to select a file from local PC and when user would click at "Upload File", form would be submitted along with the selected file:

Writing Backend JSP Script:

First let us define a location where uploaded files would be stored. You can hard code this in your program or this directory name could also be added using an external configuration such as a context-param element in web.xml as follows:

<web-app>
....
<context-param>
    <description>Location to store uploaded file</description>
    <param-name>file-upload</param-name>
    <param-value>
         c:\apache-tomcat-5.5.29\webapps\data\
     </param-value>
</context-param>
....
</web-app>

Following is the source code for UploadFile.jsp which can handle multiple file uploading at a time. Before proceeding you have make sure the followings:
  • Following example depends on FileUpload, so make sure you have the latest version of commons-fileupload.x.x.jar file in your classpath. You can download it from http://commons.apache.org/fileupload/.
  • FileUpload depends on Commons IO, so make sure you have the latest version of commons-io-x.x.jar file in your classpath. You can download it from http://commons.apache.org/io/.
  • While testing following example, you should upload a file which has less size than maxFileSize otherwise file would not be uploaded.
  • Make sure you have created directories c:\temp and c:\apache-tomcat-5.5.29\webapps\data well in advance.

<%@ page import="java.io.*,java.util.*, javax.servlet.*" %>
<%@ page import="javax.servlet.http.*" %>
<%@ page import="org.apache.commons.fileupload.*" %>
<%@ page import="org.apache.commons.fileupload.disk.*" %>
<%@ page import="org.apache.commons.fileupload.servlet.*" %>
<%@ page import="org.apache.commons.io.output.*" %>

<%
   File file ;
   int maxFileSize = 5000 * 1024;
   int maxMemSize = 5000 * 1024;
   ServletContext context = pageContext.getServletContext();
   String filePath = context.getInitParameter("file-upload");

   // Verify the content type
   String contentType = request.getContentType();
   if ((contentType.indexOf("multipart/form-data") >= 0)) {

      DiskFileItemFactory factory = new DiskFileItemFactory();
      // maximum size that will be stored in memory
      factory.setSizeThreshold(maxMemSize);
      // Location to save data that is larger than maxMemSize.
      factory.setRepository(new File("c:\\temp"));

      // Create a new file upload handler
      ServletFileUpload upload = new ServletFileUpload(factory);
      // maximum file size to be uploaded.
      upload.setSizeMax( maxFileSize );
      try{
         // Parse the request to get file items.
         List fileItems = upload.parseRequest(request);

         // Process the uploaded file items
         Iterator i = fileItems.iterator();

         out.println("<html>");
         out.println("<head>");
         out.println("<title>JSP File upload</title>"); 
         out.println("</head>");
         out.println("<body>");
         while ( i.hasNext () )
         {
            FileItem fi = (FileItem)i.next();
            if ( !fi.isFormField () )         
            {
            // Get the uploaded file parameters
            String fieldName = fi.getFieldName();
            String fileName = fi.getName();
            boolean isInMemory = fi.isInMemory();
            long sizeInBytes = fi.getSize();
            // Write the file
            if( fileName.lastIndexOf("\\") >= 0 ){
            file = new File( filePath +
            fileName.substring( fileName.lastIndexOf("\\"))) ;
            }else{
            file = new File( filePath +
            fileName.substring(fileName.lastIndexOf("\\")+1)) ;
            }
            fi.write( file ) ;
            out.println("Uploaded Filename: " + filePath +
            fileName + "<br>");
            }
         }
         out.println("</body>");
         out.println("</html>");
      }catch(Exception ex) {
         System.out.println(ex);
      }
   }else{
      out.println("<html>");
      out.println("<head>");
      out.println("<title>Servlet upload</title>"); 
      out.println("</head>");
      out.println("<body>");
      out.println("<p>No file uploaded</p>");
      out.println("</body>");
      out.println("</html>");
   }
%>


Now try to upload files using the HTML form which you created above. When you would try http://localhost:8080/UploadFile.htm, it would display following result which would help you uploading any file from your local machine.

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