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Designing a RESTful Web Application

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Re: Designing a RESTful Web Application

#21

Post by rimantas »

DougWebb wrote: post #18

Regarding response data formats, xhtml has the advantage of being both html (a format browsers know how to handle) and xml (a format that is well structured and parsable.) Semantically, xhtml can represent all of the same data structures/types as JSON: lists are UL elements, dictionaries are OL elements, numbers, strings, and booleans are really just strings in both, objects are really just dictionaries, and nulls in…

  >xhtml has the advantage of being both html
  >(a format browsers know how to handle) and
  >xml (a format that is well structured and parsable.)
And where is the advantage in that over JSON? It's just a Javascript object and browsers know very well how to handle it. That's the point.

  >Semantically, xhtml can represent all of
  >the same data structures/types as JSON
XHTML has HTML semantics, i.e. it's intended to be used to mark the structure of the text. It has no advantage for a general purpose data exchange.

  >dictionaries are OL elements
Nope. Or did you think about DL/DT/DD? Still nope.

  >numbers, strings, and booleans are really just strings in both
Nope. In JSON only strings are strings. Numbers, booleans and null are Javascript numbers, booleans and null.

  >objects are really just dictionaries
Objects are objects. Entire JSON response is an object, you can assign it to variable and use straight away.

  >and nulls in xhtml can be a special string as in JSON or an empty element.
As I said, nulls in JSON are Javascript nulls, not "some special string".

  >In both cases, the client has to either already know about
  >the data structure and how to navigate it, or can treat it
  >generically. XHTML has an advantage here; every data item
  >can be labeled with an id or class attribute to make it
  >easier to find. You can't do that in JSON unless everything
  >is a dictionary value.
Uhm. If we are talking about data in key-value then JSON has a huge advantage there. Not only you can do it in JSON, but you do exactly that and with very little overhead—that's exactly what makes JSON so attractive and popular.

var article = {"title":"Adventures in JSON land", "authors":[{"name":"Jane Doe"}], "published":false, "tags":["JSON", "Javascript", "data format"]}.

That's it. Want to access your data? It's right there:

  article.title -> "Adventures in JSON land"
  article.authors[0].name -> "Jane Doe"
  article.tags.length -> 3
Now do the same in XHTML and you will have much better understanding what advantages of JSON are.

Re: Designing a RESTful Web Application

#23

Post by RyanMcGreal »

nkohari wrote: post #22

The author seems to get confused himself about PUT vs. POST. At one point he says POST is used to create resources, and at another point he says PUT matches up roughly with SQL's INSERT (ignoring idempotence).

> It's tempting to assume that the HTTP verbs line up nicely with the SQL CRUD verbs: [...] They're superficially similar but they're not identical, and treating them as such leads to this kind of gotcha.

Re: Designing a RESTful Web Application

#24

Post by DougWebb »

rimantas wrote: post #21
DougWebb wrote: post #18

Regarding response data formats, xhtml has the advantage of being both html (a format browsers know how to handle) and xml (a format that is well structured and parsable.) Semantically, xhtml can represent all of the same data structures/types as JSON: lists are UL elements, dictionaries are OL elements, numbers, strings, and booleans are really just strings in both, objects are really just dictionaries, and nulls in…

>xhtml has the advantage of being both html >(a format browsers know how to handle) and >xml (a format that is well structured and parsable.) And where is the advantage in that over JSON? It's just a Javascript object and browsers know very well how to handle it. That's the point. >Semantically, xhtml can represent all of >the same data structures/types as JSON XHTML has HTML semantics, i.e. it's intended to be used…

The advantage of XHTML over JSON is that you don't need a specialized client to work with it. You can use the browser, which is a general-purpose client, and that will benefit you hugely during development and testing. There's a whole world of tools for testing web pages, both browser-based and library-based, and all of that can be used with your service if you use xhtml representations.

  >Nope. In JSON only strings are strings. Numbers, booleans and null are Javascript numbers, booleans and null.
I assume you've looked at a JSON message. On the wire, it's all strings. Null is represented by the four characters n, u, l, and l. It's the message parser that turns that into a real null, and an XML parser can do that too.

I'm not saying that JSON doesn't have an advantage when your client language is javascript, but even in javascript the best-practice is to use a real parser for JSON rather than just eval. If you've got to use a real parser anyway, you can also use the xml parser that's built into the browser. Combined with a library like jQuery which gives you xpath-like retrieval it's pretty easy:

    
        
            Title: Adventures in JSON land
            Authors: 
                
                    Jane Doe
                
            
            Published:false
            Tags:
                
                    JSON
                    Javascript
                    data format
Retrieve that into msg, and then:

    $("#title", msg) -> "Adventures in JSON land"
    $("#authors:first .name", msg) -> "Jane Doe"
    $("#tags li", msg).length -> 3
To be fair, an extra step is needed for turning true, false, and null into real boolean and null values. That's a solvable problem, and so is turning the xhtml into a javascript object just like the JSON parser does if that's what you want.

Also, notice that I recommended the service be able to produce BOTH json and xhtml. Special-purpose clients can use the json representation, and general-purpose clients can use the xhtml representation. That gives you the best of both worlds, and the code that produces either/or from an internal data structure is easy and small so it's not likely to introduce inconsistencies between the two representations.

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