check File Existence and display alert message

[Rohit Kumar]

Hi,

I have a servlet which uploads file to server. Below is my code and is working file. Now, I want to check if the file uploading by the user is already exists. If so , I have to display a message to user "The file you are trying to upload already exists. Do you want to overwrite" with YES or NO actions.

How can I display this alert message from user.

 
//item.write(tosave);
FileItemFactory factory = new DiskFileItemFactory();
boolean isMultipart = FileUpload.isMultipartContent(request);
System.out.println(isMultipart);
Map fileDetails = new HashMap();
ServletFileUpload upload = new ServletFileUpload(factory);
 
 
List items = upload.parseRequest(request);
Iterator iter = items.iterator();
while (iter.hasNext()) {
item = (FileItem) iter.next();
if (item.isFormField()) {
String fieldName = item.getFieldName(); 
String fieldValue = item.getString();
fileDetails.put("fileName",item.getString());
 
}
else {
fileDetails.put("path",item.getName());
cfile=new File(item.getName());
onlyFileName = cfile.getName();
}
if (! folder.exists()) folder.mkdirs();
 
 
if(cfile.exists()){ //THIS CHECK THE FILE EXISTENCE. HOW CAN I DISPLAY ALERT MESSAGE TO USER HERE.
System.out.println("File Already Exists Path is "); 
}
 

Can anyone suggest me on this?
[ October 30, 2007: Message edited by: Ben Souther ]

[sudhir nim]

You can render a new page and display the message, or you can use ajax to upload file, and if file exists on the server display an alert using ajax.

[Ulf Dittmer]

Rendering a new page informing the user is the way to go.

AJAX has no concept of files, and so can't be used for the upload.

[sudhir nim]

AJAX has no concept of files, and so can't be used for the upload.[/QB]

Why not?
You can use ajax to upload files. do some googling you will find read made code.

[Ulf Dittmer]

Originally posted by sudhir nim:
Why not?
You can use ajax to upload files. do some googling you will find read made code.

AJAX can send data to the server, but it can't upload files because JavaScript has no access to the client file system.

[Senthil Kumar]

Rohit,
You can try setting a request atribute in the servlet once you find the file already exists in the location.
1.In the JSP write a scriplet for getting the attribute value and assign it to variable declared in the scriptlet.
2.Now declare a variable in the Javascript and assign scriplet variable's value to this script variable.
3.You have to write an ONLOAD event Handler.
In that function,check the javascript variable and display the alert.
I think this will work.