Hi all
:THIS SOUNDS SIMPLE
Thanks for the response detlef but I'm still short of a simple example. How
complicated can
it be to deliver binary files (such as images) from a webserver to a webclient?
Why is it that I
need to write my own engine service???? That sounds complicated and the mere
fact that
nobody else seems willing to provide the documentation to do this only serves
to confirm my
suspicion that it is complicated!
Okay, so writing an engine service is complicated and nobody wants to document
it. Instead
I'm being asked to download an example application and then work out how the
example
works, to identify the required bits of code to do what I need and be able to
copy and
implement these in my application.
:DOESN'T EVERYBODY NEED ONE OF THESE
All of this despite the generic requirement that many web applications would
have for storing
and retrieving documents (images / blobs / etc).
:SAMPLE CONFIGURATION SUGGESTION
I realise this is an open source project so I would like to volunteer the
configuration
component necessary:
<servlet>
<servlet-name>servesBinaryFiles</servlet-name>
<servlet-class>org.somebody.SimpleBinaryServlet</servlet-class>
<load-on-startup>0</load-on-startup>
<init-param>
<param-name>binaryPath</param-name>
<param-value>/home/application/storage</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>servesBinaryFiles</servlet-name>
<url-pattern>/extimage/*</url-pattern>
</servlet-mapping>
All we need now is somebody who knows how to write the SimpleBinaryServlet to
do so.
Can we then add it into Tapestry and then we would have a solution that
everybody could
use.
:HAVE I GOT IT ALL WRONG?
Perhaps I've missed something? Is this too easy? If so then it won't take
somebody very
long to do, however as above, I'm still thinking along the lines that it's not
that simple.
Perhaps I've got it right? Is writing an engine service difficult? If so then
how can our
average web developer with a year or two of Tapestry experience be expected to
do this?
:MORE BACKGROUND ON WHAT THIS IS ALL ABOUT
And finally, just so that everybody understands the application. Consider for
example an
online shop, we upload an image of a product. We can store that image (and
perhaps a
thumbnail variation) in one of three places:
a) In the database as a BLOB (although a number of databases I have tried
experience
performance issues dealing with blobs)
b) In a directory within my webapp root (this is a very dangerous location, if
you undeploy an
application it will delete everything under the webapp root - I've had this
happen and it's not
nice) Also, by definition the webapp root is simply an expansion of the
war/ear, to store
dynamic files in this location goes against that standard. Potentially an
administrator should
be able to delete the webapp subdirectories and they should rebuild by
expansion of the
war/ear files.
c) In a directory external to my webapp root. Outside of my webapp root I'm
not going to
have any problems redeploying my application. Also, I can backup the data
(the database
and the external binary directory) separately from the programs - this is a
good thing. And
finally this method requires that I access each file via a program that can
potentially check
security settings before letting me view the file - this would be a requirement
for any CRM
style of system.
If you don't have dynamic binary files (eg images associated with database
records etc) then
you can store static images in your war file, no problem.
If your website only requires dynamic text (eg stored in a database) then you
won't need any
binary file management, again no problem.
If you do require dynamic binary files then options (a) and (b) are not great,
leaving only
option (c). My hunch is that this is a common requirement of many web
applications,
certainly it has been of the sites I have developed over the years.
:THE FINAL SUMMARY / SOLUTION
My ideal solution is that Tapestry includes a servlet engine for serving these
binary files (as
per my configuration entries above - or similar).
If I can't have the ideal the next best would be a library that provided this
functionality that I
could download.
If I can't have a library to download, the next best would be a sample
application on the faq
page showing how the engine is written and configured.
Sorry this has been so long.
Cheers
mc
On 27 Jul 2006 at 9:46, Detlef Schulze wrote:
> If you only want to stream a file to the browser the example in the faq
> is perfectly ok.
>
> If you want to do something else, for example create an image from a
> database blob or whatever for displaying it in a page, you should create
> your own engine service for that.
>
> IIRC there is an example for that (ChartService) in the demo application
> that you can download (workbench or virtual library) at least that was
> the case with tap 3.
>
> Cheers,
> detlef
>
> -----Original Message-----
> From: Murray Collingwood [mailto:[EMAIL PROTECTED]
> Sent: Donnerstag, 27. Juli 2006 09:49
> To: tapestry users
> Subject: Streaming files from Tapestry
>
> Hi all
>
> This faq page http://tapestry.apache.org/tapestry4/faq.html answers a
> common question
> people have about how to serve images or other binary files from a
> Tapestry application.
> The details are provided under:
>
> 2.6. How do I stream a file to the user from Tapestry?
>
> The example that follows works for a 'Document' type which is fine,
> however the 'disowner' at
> the bottom of the answer indicates that this is not the way this should
> be done. Also, recently
> in the forum when somebody tried this they found it only worked if you
> were sending this
> document as the only result (not as an image or other object type in the
> midst of a page).
>
> So, can somebody please document the answer to this question how it
> should be done? And
> of course - update the faq.
>
> Cheers
> mc
>
>
>
> FOCUS Computing - web design
> Mob: 0415 24 26 24
> [EMAIL PROTECTED]
> http://www.focus-computing.com.au
>
>
>
>
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