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

On Tue, Jan 28, 2014 at 3:45 PM, Matthew Butterick <mb at mbtype.com> wrote:
> 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".

There's no deep reason. It's just for backwards compatibility.

Jay

> [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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>   http://lists.racket-lang.org/users
>



-- 
Jay McCarthy <jay at cs.byu.edu>
Assistant Professor / Brigham Young University
http://faculty.cs.byu.edu/~jay

"The glory of God is Intelligence" - D&C 93