Im pretty new to struts2 and Ajax ,Actually i have a drop down menu in JSP lets say first.jsp, When user select a choice from dropdown menu,I am calling a function of Action class lets say Method1.In this method i am fetching some value from DB(lets say:a,b,c) and one value from java memory lets say d.Then I am forwarding to second.jsp and display all the parameters(a,b,c and d) in tabular format.
Now problem is that the parameter d is dynamic ,this is updating by some other application and if its change then I have to show it on JSP wihout any action.
One solution is I use in second.jsp , so after interval of 10 second again Mehod1 will call and it will fetch value(a,b,c) from db and updated value of d from java memory. and disply it to second.jsp.But in this case i am unnecessary retrieving value from db while my purpose is just to get value d from memory.This is working but this is causing my application to slower.
Can any body suggetst some other solution? or can i do it using ajax and how?
Any other advice? any help is appreciated.try to be more clear, i'm in lack of ideas in this problem, even it sounds like a classic :I have spend hours trying to play around with this but have got nowhere
Okay... What you're asking is a little fuzzy so let me rephrase:
You have a user (USER1) who opens a web page and sees some data.
You have a second user (USER2) (who may be an application) who is able set a value from time to time.
When USER2 updates that value you want USER1 to see it change in their open browser window?
If this is the case you need to understand basic ajax. For that get these demo applications working:
This example uses dojo and perhaps the S2 ajax tag lib I don't remember I prefer not to use ajax tags (as they are deprecated and prefer jquery for ajax):
http://struts.apache.org/2.x/docs/struts-2-spring-2-jpa-ajax.html
This example here shows a very similar application but using jquery, no tag library, upgraded to Spring 3, it still needs polish:
http://www.kenmcwilliams.com/Downloads/
Now that you know how to get data via ajax, look at the request with firebug. You'll see that the request is just like a typical function call, the browser keeps waiting for the data to come back.
What you do is simply not return from the action until new data is provided. This is called long polling see: http://en.wikipedia.org/wiki/Comet_%28programming%29#Ajax_with_long_polling
If you have not written a simple chat program, using just terminal windows I recommend you do so. Two windows per client (client-send, client-receive windows) and you'll need a server program. I remember hacking one together in a few hours using _Thinking In Java 2nd Edition (Later books took out the networking section if I remember correctly). Anyways between understanding client server interaction and long polling will let you get things working. It would be fun to extend the simple terminal based chat application to a S2 ajax chat application. Would make an awesome tutorial! PS: This is just an application of the producer/consumer problem (If you understand that then I guess you don't need to do the fun exercise).
The interfaces would look very pretty if the server was managed by spring. I know there must be nice servers already written but I am not familiar with any, but would love to hear of one.
Related
When I am creating a new session (or try to access from an other computer) in Vaadin Flow I get this error:
Can't move a node from one state tree to another
From this link, I read something about UI and getUIId().
However, I don't understand how I should change my application in order to fix the error.
As Denis mentioned in the forum post you linked, wrong scope sounds like the most likely culprit. In other words, you are trying to use the exact same component instance in two different UIs, when both UIs should have their own instance. It's not possible to use the same instance in two places at the same time.
You can find the documentation for Vaadin Spring scopes here: https://vaadin.com/docs/latest/flow/integrations/spring/scopes
One possible cause of errors such as that is that if you're storing a Component in a static variable. You shouldn't do that - a Component instance can only belong to a single UI. A single UI in turn (in practice) means a single browser tab.
I have little to none programming experience and I just started learning Python two weeks ago it was a pain running under windows (e.g. environment variable etc something I didn't really know what it is until two weeks ago).
I am using seleniumto try to web scrape information.
basically the url(mainly jscript) pages changes incrementally:
e.g.
http://sssss.proxy.sssss/sample#/detail/0/1
http://sssss.proxy.sssss/sample#/detail/0/2
http://sssss.proxy.sssss/sample#/detail/1/1
http://sssss.proxy.sssss/sample#/detail/1/2
http://sssss.proxy.sssss/sample#/detail/2/1
http://sssss.proxy.sssss/sample#/detail/2/2
http://sssss.proxy.sssss/sample#/detail/50/1
http://sssss.proxy.sssss/sample#/detail/50/2
I want to pragmatically and systemically webscrape specific content(find by xpath) under each page and its subpage. However, I don't know how loop works (e.g. for i to xxx) in this case because every url has to be "get" by browser web driver. (does it mean the loop will initiate the browser to open every single page or will it happen within python shell like in request package)
There are method for scraping content for url that is fixed. But in my case the url does changes so I assume it can be done differently.
Please enlighten me
With thanks,
Iverson
I'm still in a learning phase with PHP and Laravel 5 and since I upgraded to L5, I struggle with where my code belongs to. There are so many files and folders which seem to have the same purpose or at least are very similar. There are Commands, Controllers, Events, Services, Requests, etc. I give an example with my workflow and where I would place the code and I hope you guys can comment on that and correct/help me.
Situation
I want to register a new user in my application and send a welcome e-mail when he registered successfully.
Workflow
Controller (UserController): Returns requested view (register).
Request (RegisterRequest): The "RegisterRequest" validates the entered data.
Controller (UserController): Passes the validated data to the "UserRegistrar" (service) in 'App/Services'.
Service (UserRegistrar): Creates a new user and saves it to the database.
Controller (UserController): Fires the "UserWasRegistered" Event.
Event (UserWasRegistered): This Event call the "SendWelcomeEmail" Command.
Command (SendWelcomeEmail): This Command will send/queue the welcome e-mail.
Controller (UserController): Redirects the user to a view with the information that he has been registerd successfully and a message has been send to him.
Logic
Okay, let's discuss some logic:
Controller:
Doesn't hold much code.
Mainly there to return views (with requested data).
Handles workflow and "connects" modules (Services, Requests, Events).
Request: Validates the data for a specified request
Service: A service "does" something. For example it's doing requests to the database.
Event: An Event is a central place to call one or more tasks if it is fired (SendConfirmationMail, SendWelcomeMail).
Command: Mainly there to handle the logic for ONE certain task. For example sending a confirmation mail. Another command will hold the logic for sending the welcome mail. Both commands are called in the Event described before.
Repositories: What is that?!
So this is what I understand. Please help me and feed me with information.
Thanks,
LuMa
Your question is a little vague and will likely attract downvotes as being "too broad". That said, here's my take on this...
The biggest issue I see is that your application structure is very different from the recommended L5 structure - or even the standard MVC structure - that it's no wonder you're getting confused.
Let's talk about your "Logic" section:
controller - you're on the right track here. The controller is the glue between your models and your views. It can do some processing, but most should be offloaded to classes that handle specific tasks.
request - what is this? L5 includes a Request class that includes methods for examining the HTTP request received from the client. Are you talking about subclassing that? Why? If your idea of a "request" class is primarily concerned with examining input, you can either do that in your model (ie. validating stuff before sticking it in the database) or in your controller (see the L5 docs on controller validation)
service - again, what is this? You talk about "doing requests to the database", but L5 provides a class for that (DB). At a higher level, database access should primarily be done through models, which abstract away most of the low level database access. As for other services, what I usually do is create libraries to perform specific processing. For example, my application has a particular third party project management application that it accesses via an API. I have a library for that, with methods such as getProject or createProject.
event - An event is a way of ensuring that some code is called when the event happens, without a whole lot of messing about. It sounds like you have the right idea about events.
command - again, it sounds like you have the basic idea about commands.
repositories - these are way of abstracting the connection between a resource (primarily the database, but it can apply to other resources too) and the code that uses the resource. This gives a way to switch the underlying resource more easily if you (for example) decide to change database servers in the future. They are optional.
You also haven't mentioned anything about models. L5 provides an excellent way to deal with your data in understandable chunks via Eloquent models - this will make your life much easier.
My suggestion is this: start small. Build a simple MVC application with L5 - A model (to save some data), a view (to display the data), and a controller (to put the model & view together by handling the client request). Once you have that, start extending it.
There are tutorials out there that will give you this basic structure for Laravel - most are for Laravel 4, but see if you can follow the basic ideas and build something similar for Laravel 5.
I have a VS 2013 Lightswitch HTML Client application to which I've added a button that makes a Web API REST post. This basically 'refreshes' the data in the table from the original upstream source. This is all working correctly, but the operation takes a few minutes, and I want to report status to the user as it runs.
Right now, I've tried attaching a simple Refresh when the post returns as follows:
$.post("/api/data/", "Refresh", function (response) {
screen.getData().then(function (newData) { screen.reQuery(); });
});
This doesn't actually seem to do a refresh (screen.reQuery is apparently the wrong call), but the better option would be to instead have the server show progress of this long-running application.
One thought I had would be to have the server call return data in the form of "percent done" in the response as it processes it, but I don't know if this would be delivered to the client piecemeal, nor the best way to display this to the user in Lightswitch.
I'm open to other third-party libraries that might help with this, but I'd like to stick with WebAPI for commanding instead of adding something like SignalR for now, if possible. Thanks!
In general this seems like not the best idea to run operations that takes minutes on the server.
A reasonable alternative is to create a single call, that will in turn create multiple Web Jobs (see Azure Web Jobs for more info). The Web Jobs will be broken to smaller individual tasks, and your html will query the web jobs rather than your Web API.
I'm using the latest ASP.Net WebAPI Nightly builds (dated 2013-01-16).
I have a simple EF database first model at the moment that has two entities - Patients and Visits. Each patient can have many visits.
I'd like to be able to query for my list of patients and have the visits entities for each patient returned inline. I know that WebAPI's OData implementation doesn't yet support $expand. I'm hoping that just means that optional client-controlled expansion is not supported and that I can force expansion server-side.
At the moment I'm not getting any of the visits inline.
For example, my PatientController's() Get() method looks like
[Queryable(AllowedQueryOptions=AllowedQueryOptions.Supported)]
public override IQueryable<Patient> Get()
{
var query = this.entities.Patients.Include("Visits");
return query;
}
I've verified that the query executing against my database does indeed include the visit information.
To use a publicly available OData service as an example, if you use the service at http://services.odata.org/OData/OData.svc/, you can get a list of Suppliers. This is http://http://services.odata.org/OData/OData.svc/Suppliers.
You can also ask for a list of suppliers that includes the list of products using http://http://services.odata.org/OData/OData.svc/Suppliers?$expand=Products
Stepping through the ASP.NET code (via the symbols server) I've got to the System.Web.Http.OData.Formatter.Serialization.ODataEntityTypeSerializer and can see that it's CreatePropertyBag method, which builds up the list of properties to be serialized, just doesn't include the navigation properties, and they don't seem to be enumerated anywhere else apart from being written out as NavigationLinks.
I'm quite new to the ASP.NET world in general and have spent a week or so getting my head around the way things work (particularly with the changes made to OData at the end of 2012 and further changes made so far in 2013).
I suspect that if the ODataEntityTypeSerializer was to be modified (I'm happy to try) to embed this extra information in the appropriate spot (within each navigation link as an nested inline feed as best I can tell) then I'd be set.
Questions:
Have I overlooked something obvious and there's a flag I can set to turn on this behaviour? I can see why, if such a flag exists, it would be off by default (EF lazy loading and this flag wouldn't get on well)
If #1 is no, is there some other ODataEntityTypeSerializer that I could use? If so, how do I switch to it?
If #2 is no, any pointers for where I should start writing my own? Is there a place I can substitute in my own serializer or do I have to maintain my own fork of ASP.NET's Extensions project (as opposed to the Runtime project)
Thanks very much!
$expand is very high on our list of things to support for OData. But as far as I know, we don't have any flag to turn it on server-side. The formatter doesn't currently allow you to substitute your own serializers either. So I'm afraid your only option in the meantime is to create a fork and add support for $expand. If you manage to get it working, please consider sending a pull request our way:
http://aspnetwebstack.codeplex.com/SourceControl/network
You can try it already in webapi nightly builds.
Here is how to install it with nuget:
http://aspnetwebstack.codeplex.com/wikipage?title=Use%20Nightly%20Builds