This is to ask for verification-- and further info/reference if i'm wrong:
AJAX is the asynchronous go-between between the server and the client-- the operations that
are not bound to loading&reloading the web-pages.
From what i know, it's the class XMLHttpRequest handling all this asynchronousity-- all the methods and members (send(), onreadystatechange, etc.) handling/helping
the asynch operations are on XMLHttpRequest.
is this all in AJAX-- as far as its significant components go?
from what i see, XMLHttpRequest is the only vital thing in AJAX.
am i missing something here?
You are right. XMLHttpRequest is what's really the core of the ajax architecture. In a modern web app, it's most likely to be hidden under the hood ( jQuery or another javascript framework/lib ).
I remember using XMLHttpRequest for my ajax stuff like 5-6 years ago and it wasnt very user friendly but it was working.
Jquery encapsulate the XMLHttpRequest object within some methods, like get and ajax.
These methods also simplify the way the parameters are sent to and received from the server. (xml/json)
The server side part of the ajax operation is not tied to any technology. Which means you can have PHP, C# WCF/ASMX Services or something else to do the server side work.
Have a look at this, this or this for complete references for the XMLHttpRequest object.
Related
In Laravel when we using forms to store or delete a resource, the page is refreshed. What is the best technology to avoid refreshing the page while the request is being processed? AJAX, Vue.js, etc?
There are two main ways to handle http requests: synchronously and asynchronously.
Laravel is a PHP framework and therefore uses... PHP, which is a synchronous language. This implies a page refresh for every requests you make. The point is, every PHP framework have this behavior, this is the way PHP works.
So let's answer your question: indeed, you need an asynchronous technology to make a request to the server and get the response without refreshing the page. The technolodgy of choice in this case is Javascript, which will be able to make AJAX calls.
An AJAX (asynchronous JavaScript and XML) will, as stated in its name, make an asynchronous request. But an AJAX request is just the way of doing it, it's not really a technology. Yes, javascript frameworks like Vue.js are using AJAX, but that is overkill to just make some AJAX requests.
Using Axios or even jQuery is much easier and will allow you to make a request, grab the answer and modify your page without refresh very quickly :)
[EDIT]
The process to achieve what you are looking for is pretty simple:
Use Axios or jQuery to make an AJAX call (an asynchronous request)
Handle this request with Laravel, as you do for every other request
Returns something (or not, it depends of you) to alert your user that something happened
This response will be handled by Javascript
Vue is suitable for small projects where you just want to add a little bit of reactivity, submit a form with AJAX, show the user a modal, display the value of an input as the user is typing, or many other similarly straightforward things. It's scalable and also fantastic for huge project.
I have tried to incorporate AJAX into an application that I built.
The basic function is:
-The user clickes a button, which triggers JS code that makes an AJAX call that does a POST to a Servlet(sending account data).
-The Servlet(which has an EJB injected into it), communicates with an EJB through it's local interface.
-The EJB(on init) initializes a DAO object, injects an EntityManager into it, and uses that DAO object to communicate with a database through JPA (Hibernate as the provider).
-The local interface methods of the EJB return Data Transfer Objects, which are parsed in the Servlets doPost() method, and the DTO's are used to build an HTML table(String) that the Servlet responds to the AJAX call with.
-On the client side, I use that HTML table(responseText) to update a div on the page.
I have 2 questions:
1) Is using a data-centric approach to the AJAX call (returning an HTML table instead of JSON Strings) a common choice in enterprise level applications that make use of AJAX?
2)I've noticed that sometimes the POST is not even called. It seems to be intermittent. I tried to add the Cache Control header, but that doesn't seem to work. This concerns me especially when I think about eventually deploying the application to production, that maybe AJAX is not the way to go, but when it works, the application works smoothly.
1) Using AJAX to submit data or update the web page is very common. Page at a time applications are the old way web applications used to be done where you would need to reload the entire page just to update a little bit of information - which would be inefficient and not to mention would create a bad user experience. These days, updating just "Part of a page" is very common and is mostly done using AJAX, and if not WebSockets.
Now you question regarding updating the page using the servers response which is HTML - to update the page, or just get a JSON String, and manipulate the DOM (ie adding tables etc). I have used a combination of these. For example if needed to add a row to a table, you could get the server to generate the HTML using a tempting engine (groovy or similar). In addition you you need a response code, so you can package the HTML and Response code in a JSON, and send it back to the client. Any combination of these works depending on your use case.
JsonObject json = new JsonObject();
json.addProperty("responseCode", responseCode);
json.addProperty("html", html);
2) You can write a simple script to send multiple requests to the AJAX url to see if it is the server that is not able to handle the amount of requests. If it works, then you can narrow down the problem to be client side. Make sure you are not using blocking techniques. You can also setup a callback function to see if there is any response if any. AJAX Post is similar to a normal POST request, just make sure you have some indicator for the user notifying them that the request is in progress/complete.
I am new to Ajax.I found that Ajax will use XMLHTTPRequest. Can any one clarify me the usage of XMLHttpRequest without Ajax and with Ajax with an example.?
How asynchrnous Postback will occur ?
Thanks,
Rakesh.
XMLHTTPRequest is the underlying browser feature that makes what we call AJAX possible, you cannot have one without the other. Postback sounds like a reference to a .Net, which is a completely separate technology to AJAX/XMLHTTPRequest.
Find out more here
I read some paragraphs in a book saying that it is not possible to do a partial postback for web, even AJAX is employed. Ajax will postback everything and update only ajaxfied controls.
However, on pages I made using ajax, I used Fiddler to monitor the transportation. I found when the page initial load, it loaded everything include pictures .... However, when I click a button and do a ajax postback. I can only see the some data were loaded.... Looks like it doesn't need to reload the whole page again.
I don't know if what I see is correct? Or the book I read is correct?
Thank you guys.
That depends what you put in the term "postback".
The AJAX call will send the complete form data back to the server, just as if the form was posted normally. The server will answer with a partial response that only contains the parts of the page that should be updated.
So, the request is not partial, but the response is.
I am not sure how you are posting back from the client side. I am guessing you are using UpdatePanels. How well you 'AJAX-ify' a web page depends on what method you employ.
UpdatePanels - Read Dave Ward's posting on them - http://encosia.com/2007/07/11/why-aspnet-ajax-updatepanels-are-dangerous/
PageMethods to post back to a web service, get the data and update the DOM to display the result
JQuery and other such AJAX frameworks to post back to a web service
I am sure the link above should clear things up a bit
I'm having a hard time understanding your terminology. I'm not really sure what a "postback" is, much less a "partial" one. I do know that one of the basic ways to transmit information to an HTTP server is via a POST request, which is usually used when submitting forms. If you mean to say that the entire form is transmitted when you click a submit button, I believe you'd be right.
You also seem to be doing something with AJAX, but it's difficult to tell. The whole point of AJAX is to have dynamic data displayed on a page without resorting to reloading it. Defining what to send and what to do with the results is entirely up to your own JavaScript. So unless you're using a framework, which you don't specify, there is no such thing as "ajaxified controls."
In any case, "AJAX" usually means using the XMLHttpRequest() method of modern browsers to send data to servers without refreshing the page. When you call this function, you specify exactly what data to send. This has nothing to do with HTML forms. One caveat: if you are indeed using a library for AJAX, it might impose additional limits on how you structure information to send.
When an user tries to send AJAX requests simultaneously from multiple browser tabs, the earlier requests get completed and the page loads but the other AJAX calls are preempted. AS a result of which the response is empty for the other calls. Only one call survives.
In my application using struts 2.0, JSP and javascript and the prototype framework, i found that the server response is empty in the cases mentioned above though the data gets updated in teh database with the request parameters. The onSucess event handler for Ajax.request gets called but the the response is empty.
Can you please help?
Thanks
I'm not quite sure what's happening to cause this, but here's one thing to try: The last large AJAX-centric application I developed, we had to add a random number parameter to each query string to ensure there was no caching on either the client or server side (or ISP side, these days).
Guaranteeing the query URL is different in each tab could solve your problem.
I think we should get ready status from Ajax call before starting making another call to server (except you were creating a new ajax object for each call), but i could be wrong.
I never use prototype, but i use Adobe Spry for years and have no problem with multiple Ajax call, but this one is for prototype, read this it should helpful.
Multiple Ajax Requests