XForms/Saving Intermediate Form Data
NOTE – this page is in development
[edit | edit source]Saving Intermediate Form Data
[edit | edit source]This example will show you how to save intermediate form data to a local disk.
Motivation
[edit | edit source]Sometimes long forms take a while to fill out. You would like to allow users to fill out part of a form, log off, and resume their form when they return. Sometimes this intermediate data can be used as a default template for fields that are re-entered frequently by form users.
Cross Domain Posting A Security Concern
[edit | edit source]By default, XForms will not allow a form to be served from one domain and then access another domain without the user being warned. This could allow a nefarious form to access local files without authorization.
This is reflected in the fact that the "src" tag in the instance can only reference a hard-coded static string. You can not load a local file into an instance if the form was loaded from a web server.
Note that you can read and write a local file on the local file system with an XForms application that supports the file: type such as FireFox. But the forms must have this path statically coded into the XForms instance src attribute.
Steps
[edit | edit source]Step 1: Save to Client
[edit | edit source]Save instance data:
<xf:submission id="save-instance-to-client"
method="put"
action="file://C:/tmp/xforms/my-data.xml"
replace="instance"
instance="my-instance"
/>
Step 2: Read From Client
[edit | edit source]Save instance data:
<xf:submission id="read-instance-from-client"
method="get"
action="file://C:/tmp/xforms/my-data.xml"
replace="instance"
instance="my-instance"
/>
Note that to find the file you can use the <xf:upload> control:
<xf:upload ref="FilePath">
<xf:mediatype>text/xml</xf:mediatype>
</xf:upload>
The value of the action
attribute in both xf:submission
s save-instance-to-file
and read-instance-from-file
should be a variable: action="file://C:/tmp/xforms/my-data.xml"
should be automatically changed to FilePath
value.
Solution
[edit | edit source]To get this to work you have to deal with the security concerns...
Notes
[edit | edit source]There was a reference to using the chrome:// prefix not the file:// prefix on one posting..but no example was given. There was also some discussion of saving to a cookie using cookie://