file upload validation

Janoo · May 30th, 2007, 08:17 AM

hi all

i need help in getting a way to validate a file input object in Html form
i have a form where users should select a file to upload and am using jsp code to upload the file

but i want to validate that if the user didnt select a file then he should get a message which says u should select a file
using java script is possible or using jsp >>> anything would work would help me

this is my form

<FORM ACTION="single_upload_page.jsp" METHOD="POST" ENCTYPE="multipart/form-data" name="form1" id="form1">
                <br>
                <br>
                <br>
                <center>
                  <table border="2" bordercolor="#006666" >
                    <tr>
                      <td colspan="3"><center>
                          <p align="center" class="style1"><span class="style3">Upload your CV <span class="style37">using MS word or PDF files </span></span>
                              <center>
                              </center>
                        </center>
                    </tr>
                    <tr>
                      <td height="64"><span class="style2">Choose the file To Upload:</span></td>
                      <td><input name="f1" type="file" required></td>
                    </tr>
                    <tr>
                      <td colspan="2"><p align="right">
                          <INPUT name="f2" TYPE="submit" id="f2" VALUE="Upload" >
                      </p></td>
                    </tr>
                  </table>
                </center>
              </FORM></td>

Thanks in advance

iamrakesh22 · May 30th, 2007, 11:17 AM

Hi,
If you post some of the java code which deals with file upload then i can try to help you.
Usually the way is to check the available bytes in the request object using request.getInputstream().available() method call.

Regards,
Rakesh

Janoo · May 31st, 2007, 07:34 AM

hi again Rakesh

i dont have the java script .. i searched alot but didnt find a solution that's why i posted here

i tried to validate it using jsp and this is it

<%@ page import="java.io.*" %>

<%

    //to get the content type information from JSP Request Header

    //String uf = request.getParameter("f1");

    String contentType = request.getContentType();

    //here we are checking the content type is not equal to Null and as well as the passed data from mulitpart/form-data is greater than or equal to 0

    //if (uf.equals(""))
    //{
    //out.println("Please select a file to upload");

    //}

    if (contentType.equals(""))

    {
        out.println("sorry");
    }

    if ((contentType != null) && (contentType.indexOf("multipart/form-data") >= 0))

     {
         DataInputStream in = new DataInputStream(request.getInputStream());

    //we are taking the length of Content type data

        int formDataLength = request.getContentLength();

        byte dataBytes[] = new byte[formDataLength];

        int byteRead = 0;

        int totalBytesRead = 0;

        //this loop converting the uploaded file into byte code

        while (totalBytesRead < formDataLength)

        {

        byteRead = in.read(dataBytes, totalBytesRead, formDataLength);

            totalBytesRead += byteRead;

        }

        String file = new String(dataBytes);

        //for saving the file name

        String saveFile = file.substring(file.indexOf("filename=\"") + 10);

        saveFile = saveFile.substring(0, saveFile.indexOf("\n"));

        saveFile = saveFile.substring(saveFile.lastIndexOf("\\")+ 1,saveFile.indexOf("\""));

        int lastIndex = contentType.lastIndexOf("=");

        String boundary = contentType.substring(lastIndex + 1,contentType.length());

        int pos;

        //extracting the index of file

        pos = file.indexOf("filename=\"");

        pos = file.indexOf("\n", pos) + 1;

        pos = file.indexOf("\n", pos) + 1;

        pos = file.indexOf("\n", pos) + 1;

        int boundaryLocation = file.indexOf(boundary, pos) - 4;

        int startPos = ((file.substring(0, pos)).getBytes()).length;

        int endPos = ((file.substring(0, boundaryLocation)).getBytes()).length;

        // creating a new file with the same name and writing the content in new file and saving the file in a specific file

        String dir = ("C:\\Uploaded_Files\\");

        FileOutputStream fileOut = new FileOutputStream(dir+saveFile);

        fileOut.write(dataBytes, startPos, (endPos - startPos));

        fileOut.flush();

        fileOut.close();

        %>

iamrakesh22 · June 1st, 2007, 12:06 AM

Hi,

check the additional condition i've added [in bold letters]
that way we can verify whether the file selected by user is valid or not if the user just type some garbage in to the file input tag we'll get 0 bytes in the stream, or even if he completly omits it.

Code:

<%@ page import="java.io.*" %>
<%
    //to get the content type information from JSP Request Header
    //String uf = request.getParameter("f1");
    String contentType = request.getContentType();
    //here we are checking the content type is not equal to Null and as well as the passed data from mulitpart/form-data is greater than or equal to 0
    //if (uf.equals(""))
    //{
    //out.println("Please select a file to upload");
    //}
    if (contentType.equals(""))
    {
        out.println("sorry");
    }

    if ((contentType != null) && (contentType.indexOf("multipart/form-data") >= 0))
     {
         DataInputStream in = new DataInputStream(request.getInputStream());

    //we are taking the length of Content type data
        int formDataLength = request.getContentLength();

    //Check the data availability
    if(formDataLength <= 0){
        out.println("The file you've selected in empty or it does not exisits");
    }else{

        byte dataBytes[] = new byte[formDataLength];
        int byteRead = 0;
        int totalBytesRead = 0;
        //this loop converting the uploaded file into byte code
        while (totalBytesRead < formDataLength)
        {
        byteRead = in.read(dataBytes, totalBytesRead, formDataLength);
            totalBytesRead += byteRead;
        }

        String file = new String(dataBytes);
        //for saving the file name
        String saveFile = file.substring(file.indexOf("filename=\"") + 10);
        saveFile = saveFile.substring(0, saveFile.indexOf("\n"));
        saveFile = saveFile.substring(saveFile.lastIndexOf("\\")+ 1,saveFile.indexOf("\""));
        int lastIndex = contentType.lastIndexOf("=");
        String boundary = contentType.substring(lastIndex + 1,contentType.length());
        int pos;
        //extracting the index of file
        pos = file.indexOf("filename=\"");
        pos = file.indexOf("\n", pos) + 1;
        pos = file.indexOf("\n", pos) + 1;
        pos = file.indexOf("\n", pos) + 1;
        int boundaryLocation = file.indexOf(boundary, pos) - 4;
        int startPos = ((file.substring(0, pos)).getBytes()).length;
        int endPos = ((file.substring(0, boundaryLocation)).getBytes()).length;
        // creating a new file with the same name and writing the content in new file and saving the file in a specific file
        String dir = ("C:\\Uploaded_Files\\");
        FileOutputStream fileOut = new FileOutputStream(dir+saveFile);
        fileOut.write(dataBytes, startPos, (endPos - startPos));
        fileOut.flush();
        fileOut.close();
    }            
%>

You can also verify whether the file has been selected or not using java script. Try the following code.

Code:

    function checkFileExists(){
        createRequestObject();
        var file_component = document.getElementById("document");
        var filename = file_component.value;

        if(!filename || filename.length <=0){
            highlightRow(document.getElementById("document"));
            errorData[errorData.length] = "Select a document to upload.";
            return false;
        }else{
            var drive;
            if(filename.indexOf("\\")!=-1){
                drive = "\\";
            }else if(filename.indexOf("/")!=-1){
                drive = "/";
            }else{
                highlightRow(document.getElementById("document"));
                errorData[errorData.length] = "Invalid path, use browse button to select a document.";
                return false;
            }

            if((filename.substring(filename.lastIndexOf(drive)+1,filename.lastIndexOf('.'))).length >= 100){
                errorData[errorData.length] = "File name should be less than 100 characters.";

                var parent_td = document.getElementById("document").parentNode;
                parent_td.removeChild(document.getElementById("document"));
                temp_file = document.createElement("input");
                temp_file.type = "file";
                temp_file.id = "document";
                temp_file.name = "document";
                temp_file.defaultValue = "";
                temp_file.className = "element";
                temp_file.size = "35";
                parent_td.appendChild(temp_file);
                temp_file.value = "";
                return false;
            }else if(!checkValidDocs(file_component)){
                return false;
            }else
                return true;
        }

    }

Regards,
Rakesh

Janoo · June 1st, 2007, 05:32 AM

i have tried the first solution but i get an error say the saveFile is not resovled >>>> i dont know why though its indetified as it is a string

i didnt understand the java script one so i dont think i can use it

any way thanks alot Rakesh , i really appreciate that :)

iamrakesh22 · June 4th, 2007, 05:37 AM

hi,

Quote:

quote:Originally posted by Janoo
i have tried the first solution but i get an error say the saveFile is not resovled >>>> i dont know why though its indetified as it is a string

The problem is the saveFile object defined in the else block is visible only in the else block, which is not there previously [i mean before i added the if condition for validating the file size.], you might've been using it below that code [i.e. after closing the else block]. Check it you can solve it easily. If you want to use that saveFile variable outsied the else block declare it before the if condition and then assign the value in the else block.

Hope it solves your problem.

Regards,
Rakesh