Version 13 (modified by erob@…, 12 years ago) (diff)

adding ref for py-cjson et al


Here's a simple recipe that worked for me. It is quite inspired by the AjaxDojoFormSub example―and from this tutorial―except that this recipe is expected to use python-cjson for receiving JSON data.

My initial objective was to display validation errors without doing a page-refresh, by using JSON for carrying errors (or whatever else you could possibly imagine) back to the client browser.

The server view

First thing first, lets write the server view, as its really important to make the forms working without the use of Javascript:

import cjson
from django.http import HttpResponse
from django.template import loader, Context

def register(request):
    # Register or reports any (new)form-validation errors using JSON.
    form = ExampleForm(request.POST)
    t = loader.get_template('myform.html')
    if not form.is_valid():
       # Return JSON object containing the errors object.
       if xhr:
          return HttpResponse(cjson.encode(form.errors), mimetype='text/javascript')
          # vanilla Http response fallback
          return HttpResponse(t.render(Context({'errors' : form.errors }))
       # Do something when the form has been validated.

The client view

Now that the server view is writtent, we could try next to arrange the client code to fit into one, unportable template chunk, however it's usually best to split the work in smaller pieces, at least for being nice to the maintainers (You). :-)

So let's move on in writing our own Dojo template, where we will make an abstraction of all our applied Dojo concepts.

Quite frankly, that part is going straight-forward, as we're only writing HTML:

<script type="text/javascript">
    djConfig = {
<script type="text/javascript" src="/media/js/dojo/dojo.js"></script>
<script type="text/javascript">
    dojo.require("dojo.event.*");       // sophisticated AOP event handling
    dojo.require("*");          // for Ajax requests
    dojo.require("dojo.json");          // serialization to JSON
<script type="text/javascript" src="/media/js/ajax.js"></script>

The djConfig.isDebug parameter is important for debugging, so you should consider setting it to "true" when inspecting you're application with Firebug or something else.

Optionally, you can "bake" your own Dojo file, and substract the baked modules from the list of required modules above, so we wont load the already compiled Dojo modules twice.

Form validating w/

Let's complete our application by writing down the core JS file, for doing some-cute-AJAX-related-things-with-Dojo:

function validate() {
    var fNode = dojo.byId('xForm') 
    var fParms =
    var bindArgs = {
        url: ".",
        mimetype: 'text/json',
        method: "post",
        preventCache: true,
        transport: "XMLHTTPTransport",
        postContent: fParms,
        error: function(type, error){
               // Handle errors for the XMLHTTPTransport here.
               return false
        load: function(type, data, evt){
              // handle successful response here
              if(type == 'load'){
                var myDiv = dojo.byId('errorBox1')
                // XXX Not sure what to do if the data is JSON or
                // something else..
                var json = dojo.json.evalJson(data)
                   errStr = ''
                   for(x in json){
                     errStr += x + ': ' + json[x] + '<br />'
                   myDiv.innerHTML = errStr
                   myDiv.innerHTML = "hello, world!"
       var xmlhttp =
       return xmlhttp

Notice the absence of the formNode param for postContent, and the presence of to parse/encode the form data into a proper format. That is all required for having the XMLHTTPRequest object handled by the Dojo toolkit.

To connect the input submit button with the JS callback, use the following line:

<input type="button" onclick="validate()" id="fooBtn"></input>

Have fun! That recipe should work in Firefox 2 and Opera 9.10.


  • Usability issues: HTML 4.01 vs XHTML 1.0 strict vs No javascript
  • How to display other mimetype(s) when JSON is not used?


Add some notes here.


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