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412

Chapter 16 Using HTML Forms

16.7 File Upload Controls

HTML Element:

 (No End Tag)

Attributes:

NAME

 (required), 

VALUE

 (ignored), 

SIZE

, 

MAXLENGTH

, 

ACCEPT

, 

ONCHANGE

, 

ONSELECT

, 

ONFOCUS

, 

ONBLUR

 (nonstandard)

This element results in a filename textfield next to a Browse button. Users

can enter a path directly in the textfield or click on the button to bring up a

file selection dialog that lets them interactively choose the path to a file.

When the form is submitted, the contents of the file are transmitted as long

as an 

ENCTYPE

 of 

multipart/form data

 was specified in the initial 

FORM

declaration. This element provides a convenient way to make user support

pages, where the user sends a description of the problem along with any asso 

ciated data or configuration files.

Core Tip

Always specify 

ENCTYPE="multipart/form data"

 in forms with file 

upload controls.

NAME

The 

NAME

 attribute identifies the textfield when the form is submitted.

VALUE

For security reasons, this attribute is ignored. Only the end user can 

specify a filename. 

SIZE and MAXLENGTH

The 

SIZE

 and 

MAXLENGTH

 attributes are used the same way as in text 

fields, specifying the number of visible and maximum allowable charac 

ters, respectively.

ACCEPT

The 

ACCEPT

 attribute is intended to be a comma separated list of 

MIME types used to restrict the available filenames. However, very few 

browsers support this attribute.

Second edition of this book: www.coreservlets.com; Sequel: www.moreservlets.com.

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