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file upload

alec stewart stewart
Ranch Hand

Joined: Dec 23, 2003
Posts: 71
how do i upload a file.
i have an html file whose enctype=multipart/form data
besides a file field in the html document i have other elements also like textboxes and select boxes.
now how in the servlet i get these parameters (req.getParameter)when form enc type is multipart/form data
himanshu patel
Ranch Hand

Joined: Feb 03, 2003
Posts: 205
I would encourage you to make use of search facility.This topics had been
discussed many times in past.You will certainaly get what you want.

If you want to become a rich, do not work for others but make others to work for you.
danny liu
Ranch Hand

Joined: Jan 22, 2004
Posts: 185
The HttpServletRequest cannot recognize the multipart format message.
What you could do are:
a. write a wrapper request which include the functionality to read the multipart message.
b. download a customized wrapper from internet.
just go to, go to the servlet forum, there are a lot of
info about this sort of wrapper.
Hope it helps
R. Shellbay

Joined: Sep 19, 2003
Posts: 13
The Jakarta project commons have a FileUpload thingy.
This include among other a multipartfomrparser...
Jakarta Commons
Senthil B Kumar
Ranch Hand

Joined: Feb 09, 2004
Posts: 160
The HTML form where there is a input type file control then its enc type should be as follows
The enctype attribute of the FORM element specifies the content type used to encode the form data set for submission to the server. User agents must support the content types listed below. Behavior for other content types is unspecified.
This is the default content type. Forms submitted with this content type must be encoded as follows:
Control names and values are escaped. Space characters are replaced by `+', and then reserved characters are escaped as described in [RFC1738], section 2.2: Non-alphanumeric characters are replaced by `%HH', a percent sign and two hexadecimal digits representing the ASCII code of the character. Line breaks are represented as "CR LF" pairs (i.e., `%0D%0A').
The control names/values are listed in the order they appear in the document. The name is separated from the value by `=' and name/value pairs are separated from each other by `&'.
Note. Please consult [RFC2388] for additional information about file uploads, including backwards compatibility issues, the relationship between "multipart/form-data" and other content types, performance issues, etc.

The content type "application/x-www-form-urlencoded" is inefficient for sending large quantities of binary data or text containing non-ASCII characters. The content type "multipart/form-data" should be used for submitting forms that contain files, non-ASCII data, and binary data.
The content "multipart/form-data" follows the rules of all multipart MIME data streams as outlined in [RFC2045]. The definition of "multipart/form-data" is available at the [IANA] registry.
A "multipart/form-data" message contains a series of parts, each representing a successful control. The parts are sent to the processing agent in the same order the corresponding controls appear in the document stream. Part boundaries should not occur in any of the data; how this is done lies outside the scope of this specification.
As with all multipart MIME types, each part has an optional "Content-Type" header that defaults to "text/plain". User agents should supply the "Content-Type" header, accompanied by a "charset" parameter.
Each part is expected to contain:
a "Content-Disposition" header whose value is "form-data".
a name attribute specifying the control name of the corresponding control. Control names originally encoded in non-ASCII character sets may be encoded using the method outlined in [RFC2045].
Thus, for example, for a control named "mycontrol", the corresponding part would be specified:
Content-Disposition: form-data; name="mycontrol"
As with all MIME transmissions, "CR LF" (i.e., `%0D%0A') is used to separate lines of data.
Each part may be encoded and the "Content-Transfer-Encoding" header supplied if the value of that part does not conform to the default (7BIT) encoding (see [RFC2045], section 6)
If the contents of a file are submitted with a form, the file input should be identified by the appropriate content type (e.g., "application/octet-stream"). If multiple files are to be returned as the result of a single form entry, they should be returned as "multipart/mixed" embedded within the "multipart/form-data".
The user agent should attempt to supply a file name for each submitted file. The file name may be specified with the "filename" parameter of the 'Content-Disposition: form-data' header, or, in the case of multiple files, in a 'Content-Disposition: file' header of the subpart. If the file name of the client's operating system is not in US-ASCII, the file name might be approximated or encoded using the method of [RFC2045]. This is convenient for those cases where, for example, the uploaded files might contain references to each other (e.g., a TeX file and its ".sty" auxiliary style description).
The following example illustrates "multipart/form-data" encoding. Suppose we have the following form:
<FORM action=""
What is your name? <INPUT type="text" name="submit-name"><BR>
What files are you sending? <INPUT type="file" name="files"><BR>
<INPUT type="submit" value="Send"> <INPUT type="reset">

If the user enters "Larry" in the text input, and selects the text file "file1.txt", the user agent might send back the following data:
Content-Type: multipart/form-data; boundary=AaB03x
Content-Disposition: form-data; name="submit-name"
Content-Disposition: form-data; name="files"; filename="file1.txt"
Content-Type: text/plain
... contents of file1.txt ...
If the user selected a second (image) file "file2.gif", the user agent might construct the parts as follows:
Content-Type: multipart/form-data; boundary=AaB03x
Content-Disposition: form-data; name="submit-name"
Content-Disposition: form-data; name="files"
Content-Type: multipart/mixed; boundary=BbC04y
Content-Disposition: file; filename="file1.txt"
Content-Type: text/plain
... contents of file1.txt ...
Content-Disposition: file; filename="file2.gif"
Content-Type: image/gif
Content-Transfer-Encoding: binary
...contents of file2.gif...

So this form should be submitted to Servlet in the server, and in the servlet you have to decode the request using the boundary, identify the individual controls , their names and their values.......
there are few 3rd party Servlets available doing the above work....

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