[racket] web server: leading forward slash required in paths?

The behavior is correct. It's just not the behavior you want.

When you start up the web server, the default URL for the page is:

http://localhost:8000/servlets/standalone.rkt

So "/puppy.jpg" really means this:

http://localhost:8000/puppy.jpg

Which works, because puppy.jpg is in server-root-path. Whereas the relative
URL "puppy.jpg" means this:

http://localhost:8000/servlets/puppy.jpg

And indeed, you get no puppy, because the server is looking in the
subdirectory "servlets", which doesn't exist in your server-root-path.

Thus you have two choices:

1) Add the #:servlet-path parameter, which lets you attach the servlet to a
URL at the top level, like so:

(serve/servlet
 start
 #:server-root-path SOMEPATH
 #:servlet-path "/standalone.rkt"
 )

Now when you start the web server, the URL for the page will be:

http://localhost:8000/standalone.rkt

And when you link to "puppy.jpg" (no forward slash), it will mean:

http://localhost:8000/puppy.jpg

And you will get a puppy. (Of course, "/puppy.jpg" will still work.)

2) Keep your existing server configuration and instead put a "servlets"
subdirectory within D:/Tobias/server-root/htdocs/, and puppy.jpg within it.
Then you can use "puppy.jpg" as a relative URL.

The docs for serve/servlet cover servlet-path [1], though your question is
fair because this consequence is a little unexpected. I don't know the
policy reason for having the default servlet-path
be "/servlets/standalone.rkt" rather than something at the top level, like
"/standalone.rkt".

[1] http://docs.racket-lang.org/web-server/run.html?q=serve/servlet



On Tue, Jan 28, 2014 at 1:38 PM, Janos Tobias Locsei <jtlocsei at cantab.net>wrote:

> Hi Matthew,
>
> Here's an example without using templates, but the same sort of behavior
> applies when using templates too.
>
> #lang racket
>
> (require web-server/servlet
>          web-server/servlet-env)
>
> (define SOMEPATH
>   (build-path "D:\\Tobias\\server-root"))
>
> (define (start request)
>   (response/xexpr
>    `(html (head (title "Hello world"))
>           (body (h1 "Hello world")
>                 (img ([src "/puppy.jpg"] [alt "cute puppy"]))))))
> ; puppy.jpg is located at D:/Tobias/server-root/htdocs/puppy.jpg
> ; Image only displays if I use the leading forward slash like this
>
> (serve/servlet
>  start
>  #:server-root-path SOMEPATH
>  )
>
> I noticed that the leading forward slash is used in the web applications
> tutorial of the racket documentation, e.g. when referencing a css file
> (search page for "test-static.css"):
> http://docs.racket-lang.org/continue/
>
> Tobias
>
>
>
>
> On 28 January 2014 19:27, Matthew Butterick <mb at mbtype.com> wrote:
>
>> I've not experienced this issue with the Racket web server. When you
>> append a leading forward slash to a URL, you're obviously telling the
>> browser something completely different about where to find the file. I
>> would suspect it has something to do with either file organization, Racket
>> web server configuration, or both.
>>
>> Where are myimage.jpg and mytemplate.html in relation to one another? In
>> the same directory?
>>
>>
>> On Tue, Jan 28, 2014 at 7:04 AM, Janos Tobias Locsei <jtlocsei at cantab.net
>> > wrote:
>>
>>> I noticed that when using the racket web server one needs to include a
>>> leading forward slash when referencing static files e.g. a style.css or an
>>> image.jpg. Is there a rationale for this? It's different than the usual
>>> html convention, and it means that when using html template files it's not
>>> possible to preview the template in the web browser without running the web
>>> server.
>>>
>>> For example, I have a file mytemplate.html that includes the line
>>>
>>> <img src="/myimage.jpg" />
>>>
>>> The leading "/" is required for the image to be found by the racket web
>>> server but it means that I can't preview mytemplate.html in my web browser
>>> without first firing up the racket web server.
>>>
>>> It's not a big deal but I'm just wondering if there's a way around this.
>>>
>>> Tobias
>>>
>>>
>>>
>>>
>>>
>>> ____________________
>>>   Racket Users list:
>>>   http://lists.racket-lang.org/users
>>>
>>>
>>
>
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