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.
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 am a complete newbie to AngularJS. I want to check the feasibility of using it in my new Project which is a web application. I already have a few pages created in project using Struts2 Spring and hibernate. To convert these following are points I understand:
Convert server side API to REST style which returns JSON data
Question: Can I use dynamic HTML to load using AngularJS. I guess yes. not sure how?
Currently I use velocity Templates on server side to populate data in HTML templates and send it as response in AJAX? What would change if i try to use AngularJS?
I have a landing page which is used to show some images and data associated with it which is stored in DB. How can I show it using AngularJS?
Question: Shall I load the HTML template which contains only one div tag when I hit website URL(mysite.com) and then fire AJAX requests to load the dynamic HTML?
If I use AndularJS does it invalidate use of Struts2 altogether if I choose to implement my Data API as REST with JSON? I guess not as I will still need to load dynamic HTML views which will be generated on Server correct?
How to maintain HTTP session state on server side if I use REST data API with AngularJS on client?
I know I can search and read about answers to above questions on net somewhere. I just need them at one place so that I can carry discussion and other questions that arise from it.
I may answer some of your questions:
1) Convert server side API to REST style which returns JSON data
Yes
Question : Can I use dynamic HTML to load using AngularJS. I guess
yes. not sure how?
Currently I use velocity Templates on server side to populate data in HTML templates and send it as response in AJAX? What would change
if i try to use AngularJS?
If I understood you right, you want to generate templates on server-side. In this case - you just don't need AngularJs - your views are prepopulated on server and browser recieves static content (from client-side point of view). If you want to use AngularJs, then your templates will become static content (from server-side point of view) and they will be populated by angular via REST services.
2) I have a landing page which is used to show some images and data
associated with it which is stored in DB. How can I show it using
AngularJS?
Question : Shall I load the HTML template which contains
only one div tag when I hit website URL(mysite.com) and then fire AJAX
requests to load the dynamic HTML?
Not exactly. One div would be enough for jQuery-based approuch (you would use something like $.ajax and then appended data in imperative way). In case of Angular you will need to return template. It may look like this:
<ul ng-controller="MyCtrl">
<li ng-repeat="item in data">
<img ng-src="item.image.src">
<span>{{item.data.someTextProperty}}</span>
</li>
</ul>
And some AngularJs controller that will fire request to REST service (via your AngularJs service, probably) and autmatically fill template with results
function MyCtrl($scope, $http) {
$http.get('/rest/data').success(function(result) {
$scope.data = result;
});
}
3) If I use AndularJS does it invalidate use of Struts2 altogether if
I choose to implement my Data API as REST with JSON? I guess not as I
will still need to load dynamic HTML views which will be generated on
Server correct?
I think it will only invalidate use of View of MVC in Struts, since AngularJS will just replace it. Also it will make you to use something like RESTful controllers (not quite familliar with Struts, but I think there is something like this)
4) How to maintain HTTP session state on server side if I use REST
data API with AngularJS on client?
This is not short answer, but basically there is following pattern. AngualrJs provides http interceptors, that may intercept requests and responses. If response with code 401 (which is unauthorized) is intercepted, you may provide your user with a login form to restore session and after this action will be completed, retry last request. Also, here you may find another aspect of this question.
I hope my answer helped you.
Greeting to the community. This is my very first question.
I had in mind to add Livezilla live support in my MVC website, but I realised that there are some problems.
First of all, it is written in php and mysql, so is it possible to comply with MVC and sql server?
Does anybody know a similar solution (like livezilla) in my case?
PS. Excuse my poor english...
you could even look into using an iFrame to run livezilla inside of an mvc3 page if you wanted.
or, you could roll your own. if you wanted to try implementing a live response mvc3 page look into jquery and ajax asynchronous calls such as $.post and also look into the extension for controller AsyncController, and [AsyncTimeout(XXX)]. you will also have to read up on sending and receiving json objects in ajax and from a controller to the view.
Simple psuedo:
View:
setTimeOut calls a javascript function every X milliseconds
the javascript function uses json to wrap page data and pass it to the controller inside a $.post() call
Controller:
recieves page data as an model object in a post
determines if page is out of sync or not
returns relevant sync data in a json object back to the view
View:
the same javascript function receives the json object from controller
updates the page based on relevant sync data
Problem solved. I just uploaded the folder given from livezilla in the root folder of my website. Then the only need to met is to have a Mysql server to create the database for livezilla. After that php and mvc runs together with no problem.
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