I'm wondering: if I were a a router, packet inspector, firewall, or other packet-sniffing device (which I'm glad I'm not) would I be able to tell the difference between a traditional HTTP request and an XMLHttpRequest? Less theoretically, is it possible that some ISP or (let's say) cell phone data provider could restrict XMLHttpRequest traffic without interrupting HTTP service?
Thanks.
There's nothing at the packet level to distinguish them because and XMLHttpRequest is an HTTP request. The XML bit refers to the fact that if the response is of an xml Content-Type then the responseXML method will return a DOM Object.
To the best of my knowledge, there is no fundamental difference - so from the point of view of a router etc. you can't tell in general.
But I do believe that most popular Javascript toolkits will add an HTTP header to their XMLHttpRequests to identify them as such. I forget the name, though...
EDIT: Here's an example (top Google hit for "jquery xmlhttprequest header", no quotes) that shows that jQuery apparently sets X-Requested-With to "XMLHttpRequest".
at packet, network, session levels: no.
at application level, that is with an HTTP-specific device like a filtering proxy, maybe.
i'd check the HTTP request headers. they might (just might) have some differences. but i'm sure any difference there would be very browser-specific, and quite probably the right JavaScript code could insert the appropriate headers to make it totally indistinguishable.
in short: check the HTTP headers; but don't expect it to be general, much less useful.
Related
I'd like to accept and respond to JSON requests in Odoo from sources that may be out of my control. The reason this is not straightforward is because Odoo is forcing me to use JSON-RPC, which is not suitable for the source I'm interacting with.
For example, if I set the route type to http in the #http.route decorator, Odoo rejects the request if the mimetype is application/json but the body has no content. This isn't going to work in my case because I may not be able to choose what the other source sends to me. Additionally, I am unable to send back a custom JSON response unless the incoming request doesn't have the application/json mimetype, which again is not in my control.
I have done a lot of searching on the internet and read much of Odoo's HTTP source code. The "solution" I keep seeing everywhere is to monkey patch the JsonRequest class one way or another. This allows me to indeed respond with whatever I want, however it doesn't allow me to accept whatever the service may send me.
One specific case I need to be able to handle is incoming application/json GET requests with no body. How can I achieve this despite Odoo's heavy handed JSON-RPC handing?
There is no correct way to accomplish this, I'd call the described method acceptable. It applies to versions of Odoo 10 through 15.
In my opinion, it would be better to leave JsonRequest class alone and let it do its JSON-RPC related job. There is odoo.http.Root.get_request method which constructs the json-rpc or http request object, depending on the content type:
class Root(object):
"""Root WSGI application for the OpenERP Web Client.
"""
# ...
def get_request(self, httprequest):
# deduce type of request
if httprequest.mimetype in ("application/json", "application/json-rpc"):
return JsonRequest(httprequest)
else:
return HttpRequest(httprequest)
This point seems to be the most relevant one to be patched, with returning the custom request class object from this method. There is an issue, though - this method is called prior to any route detection. You have to invent a suitable method to tell, which request class object to return.
To have an idea about a possible implementation, please, see OCA base_rest module.
I understand what a HEAD request is, and what it could be used for. Will any standard, modern browser ever send a HEAD request? If so, in what context?
A browser will send a HEAD request if that is explicitly requested in an XMLHttpRequest, but I'm fairly certain that the browser will never send a HEAD request of its own accord. My evidence is that the Tornado web server defaults to returning an error for HEAD requests and I've never heard of anyone running into problems related to this (or even being aware of it).
HEAD is mostly obsolete IMHO: on a dynamic web site it is unlikely to be significantly more efficient than a GET, and it can usually be replaced by one of the following:
Conditional GET with If-Modified-Since or If-None-Match (used for caching)
Partial GET with Range header (used for e.g. streaming video)
OPTIONS (used for CORS preflight requests)
I know that XMLHttpRequest and ServletRequest are not different in theory by searching similar questions.
But some details confuse me.
Fox example, if I send an XMLHttpRequest to the server, how does the client know the response is for the XMLHttpRequest rather than for the ServletRequest?
How does the client distinguishes the response type?
Otherwise, on the server side, when I call method:
response.getWriter().write(str);
Will the argument str be present on the browser?
This may be of help to you.
while the standard HTTP request makes a 'synchronous' call and must wait for the response and makes a page-reload (you always get a new html-page to display) a XMLHttpRequest may be used sync (not typical) and async (the better way) without a page-reload. you may ask for the response with javascript and the response is usually xml- or json-data that you may process with js and update parts of your page through the use of dom-methods that manipulate your document ... so you don't need an entire page-reload because all of that is running in the 'background' ...
This should also help with how the two requests are treated differently by servers and clients.
I have a program that is supposed to interact with a web server and retrieve a file containing structured data using http and cgi. I have a couple questions:
The cgi script on the server needs to specify a body right? What should the content-type be?
Should I be using POST or GET?
Could anyone tell me a good resource for reading about HTTP?
If you just want to retrieve the resource, I’d use GET. And with GET you don’t need a Content-Type since a GET request has no body. And as of HTTP, I’d suggest you to read the HTTP 1.1 specification.
The content-type specified by the server will depend on what type of data you plan to return. As Jim said if it's JSON you can use 'application/json'. The obvious payload for the request would be whatever data you're sending to the client.
From the servers prospective it shouldn't matter that much. In general if you're not expecting a lot of information from the client I'd set up the server to respond to GET requests as opposed to POST requests. An advantage I like is simply being able to specify what I want in the url (this can't be done if it's expecting a POST request).
I would point you to the rfc for HTTP...probably the best source for information..maybe not the most user friendly way to get your answers but it should have all the answers you need. link text
For (1) the Content-Type depends on the structured data. If it's XML you can use application/xml, JSON can be application/json, etc. Content-Type is set by the server. Your client would ask for that type of content using the Accept header. (Try to use existing data format standards and content types if you can.)
For (2) GET is best (you aren't sending up any data to the server).
I found RESTful Web Services by Richardson and Ruby a very interesting introduction to HTTP. It takes a very strict, but very helpful, view of HTTP.
Is it allowable to pass parameters to a web page through the URL (after the question mark) when using the POST method? I know that it works (most of the time, anyways) because my company's webapp does it often, but I don't know if it's actually supported in the standard or if I can rely on this behavior. I'm considering implementing a SOAP request handler that uses a parameter after the question mark to indicate that it is a SOAP request and not a normal HTTP request. The reason for this that the webapp is an IIS extension, so everything is accessed via the same URL (ex: example.com/myisapi.dll?command), so to get the SOAP request to be processed, I need to specify that "command" parameter. There would be one generic command for SOAP, not a specific command for each SOAP action -- those would be specified in the SOAP request itself.
Basically, I'm trying to integrate the Apache Axis2/C library into my webapp by letting the webapp handle the HTTP request and then pass off the incoming SOAP XML to Axis2 for handling if it's a SOAP request. Intuitively, I can't see any reason why this wouldn't work, since the URL you're posting to is just an arbitrary URL, as far as all the various components are concerned... it's the server that gives special meaning to the parts after the question mark.
Thanks for any help/insight you can provide.
Lets start with the simple stuff. HTTP GET request variables come from the URI. The URI is a requested resource, and so any webserver should (and apache does) have the entire URI stored in some variable available to the modules or appserver components running within the webserver.
An http POST which is different from an http GET is a separate logical call to the webserver, but it still defines a URI that should process the post. A good webserver (apache being one) will again make the URI available to whatever module or appserver is running within it, then will additionally make available the variables which were sent in the POST headers.
At the point where your application takes control from apache during a POST you should have access to both the GET and POST variables and be able to do whatever control logic you wish, including replying with a SOAP protocol instead of HTML.
If you are asking whether it is possible to send parameters via both GET and POST in a single HTTP request, then the answer is "YES". This is standard functionality that can be used reliably AFAIK.
One such example is sending authentication credentials in two pieces, one over GET and the other through POST so that any attempt to hijack a session would require hijacking both the GET and POST variables.
So in your case, you can use POST to contain the actual SOAP request but test for whether it is a SOAP request based on the parameter passed in GET (or in other words through the URL).
I believe that no standard actually defines the concept of "HTTP parameters" or "request variables". RFC 1738 defines that an URL may have a "search part", which is the substring after the question mark. HTML specifies in the form submission protocol how a browser processing a FORM element should submit it. In either case, how the server-side processes both the search part and the HTTP body is entirely up to the server - discarding both would be conforming to these two specs (but fairly useless).
In order to determine whether you can post a search part to a specific service, you need to study this service's protocol specification. If the service is practically defined by means of a HTML form, then you cannot use a mix - you can't even use POST if the FORM specifies GET (and vice versa). If you post to a web service, you need to look at the web service's WSDL - which will typically mandate POST; with all data in a SOAP message. Etc.
Specific web frameworks may have the notion of "request variables" - whether they will draw these variables both from a search part and a request body, you need to find out in the product documentation.
I deployed a web application with 3 (a mobile network operator) in the UK. It originally used POST parameters, but the 3 gateway stripped them (and X-headers as well!). So beware...
allowable? sure, it's doable, but i'm leaning towards the spec suggesting dual methods isn't necessarily supposed to happen, or be supported. RFC2616 defines HTTP/1.1, and i would argue suggests only one method per request. if you think about your typical HTTP transaction from the client side, you can see the limitation as well:
$ telnet localhost 80
POST /page.html?id=5 HTTP/1.1
host: localhost
as you can see, you can only use one method (POST/GET, etc...), however due to the nature of how various languages operate, they may pick up the query string, and assign it to the GET variable. ultimately though, this is a POST request, and not a GET.
so basically, yes this functionality exists, is it intended? i would say no.