If I want to call a server function from JavaScript to retrieve a name of a person from a database (just as an example)... and I went...
name = myServices.getName(userId);
If I have a script manager with a service reference to a .asmx file that has the web method getName( int userId ) {} then this function should be called properly and would, eventually, return the name for that userId.
Unfortunately, I want to do...
name = myServices.getName(userId);
alert(name);
however, when doing ASP.NET AJAX, it would call the web method and continue executing before waiting for a response from the server (which I understand is the point of AJAX, to stop the browser from freezing while waiting for data)
I need to get the name back from the server before I can continue executing... How can I approach this to fix this issue?
There is a method you can add as a parameter to the service method that will call the method on success where you can do other stuff.
For example:
function test() {
PageMethods.MyMethod("name", OnMyMethodComplete);
}
function OnMyMethodComplete(result, userContext, methodName) {
alert(result);
}
If you want to call a Web method synchronously, you'll need to set up the request manually and use a Sys.Net.XMLHttpSyncExecutor.
Here's an example (see ExecuteSynchronously function).
For a JavaScript solution, you could loop until name has a value. Adjust time-based on latency to keep app responsive
var time = 100;
window.setTimeout(name == '' ? wait : continue, time);
function wait() {
window.setTimeout(name == '' ? wait : continue, time);
}
function continue() {
//code having to do with name
alert(name);
}
Congratulations! You've taken your first step into a larger asynchronous world. I'd definitely go with using the callbacks that CSharpAtl suggested.
Related
I have a method in .NET (GetDataStationParts), which I declare with 2 parameters, I want to call it from a JavaScript, and I use the InvokeMethodAsyn function in this way:
const { data } = require("jquery");
function GetParteScrap()
{
var idestacionjs = document.getElementById('getestacion');
var idmodelojs = document.getElementById('getmodelo');
var tablascrap = DotNet.InvokeMethodAsyn("YMMScrapSystem", "GetDataStationParts", idestacionjs, idmodelojs);
console.log(tablascrap);
}
To do it, I base it on an example on the web but I'm not sure where it gets the DotNet object to then invoke the method, the intention of my code is that after selecting parameters of 2 , go to the database and execute a SQL-level function, which will return a table, with the function GetDataStationParts, I try to give it the functionality to execute my method at the DB level as follows
[JSInvokable]
public async Task<IEnumerable<GetEstacionParte>>GetDataStationParts(int modelo, int estacion)
{
var resul = await _context.Set<GetEstacionParte>().FromSqlInterpolated($"SELECT * FROM dbo.GetEstacionParte({modelo},{estacion})").ToArrayAsync();
return resul;
}
The SQL level function works correctly, but when running the application at the console level in the browser, it throws the following error, where it indicates that the function is not defined
Where could the error be? Thank you for reading
require() is not a feature that is built into the browser. Javascript environment does not understand how to handle require(), In Node.js by Default this function is available.
I suspect you most probably missing some reference here. You can either download require.js from here & link with your application or use below script tag.
<script src="https://requirejs.org/docs/release/2.3.5/minified/require.js"></script>
I am toying with Ajax-Enabled WCF services. So far I've managed to create and consume my service with a small client application. However while reading the "How-to" page on the msdn website, I've came accross this piece of code :
function Button1_onclick() {
var service = new SandwichServices.CostService();
service.CostOfSandwiches(3, onSuccess, null, null);
}
function onSuccess(result) {
alert(result);
}
and I fail to understand (or even find information about) the null, null parameters when calling the function. 3 is the parameter you want to pass to the service function, onSuccess is the function that is called on a successfull callback but what are those 2 null parameters ?
The last two parameters refer to onFailure and Usercontext respectively for below mentioned question.
service.CostOfSandwiches(3, onSuccess, null, null);
OnFailure : As the name suggest, if ajax call fails because of network issue, server error, timeout etc.., function passed here as argument will invoked.
UserContext: Generally all ajax call (I mean this[WCF Ajax] is too dependent on ajax call) uses this parameter. Because, there is a main method that call $.ajax, in your case it is Button1_onclick. So upto this point all variables defined will not be available in callbacks ( success or failure), because these are called back when ajax call completes, but to make those call aware of previously defined variable, context option is used to pass them.
Example:
function Button1_onclick() {
var service = new SandwichServices.CostService();
var some_var = "someval"; // on successcallback if you are trying to access this, it will show error.
service.CostOfSandwiches(3, onSuccess, null, null);
}
To use this in success callback , you have to pass that as usercontext object -- like this service.CostOfSandwiches(3, onSuccess, null, some_var);
OnSuccessMethod -
function onSuccess(result,usctx,methodname)
{
if (usctx == "someval")
{
alert(result);
}
}
For more info on context option in general ajax sense , refer this - How to pass context in jquery ajax success callback function
They are callbacks for sucess, error, and userContext. You can read a bit more here under the "Accessing WCF web services" section.
There is a scenario in which a user terminates the application, while it is still processing data via BackgroundWorker.
I would like to send cancel or terminate command to this method. I tried calling CancelAsync() method, but it obviously didn't work the way I expected and the worker still continued processing.
What is a good way to signal the BackgroundWorker, and especially its RunWorkerCompleted method to stop processing?
Do I have to use state variables?
This is the code executed when you call CancelAsync() on a BackgroundWorker
public void CancelAsync()
{
if (!this.WorkerSupportsCancellation)
{
throw new InvalidOperationException(SR.GetString
("BackgroundWorker_WorkerDoesntSupportCancellation"));
}
this.cancellationPending = true;
}
As you can see, they set the internal cancellationPending variable to true after checking the value of WorkerSupportsCancellation.
So you need to set WorkerSupportsCancellation = true;, when you exit from your app call backGroundWorkerInstance.CancelAsync() and inside the DoWork or RunWorkerCompleted test the CancellationPending. If it's true stop your process.
Let's say I have a simple controller like this:
class FooController {
def index = {
someVeryLongCompution() //e.g crawl a set of web pages
render "Long computation was launched."
}
}
When the index action is invoked, I want the method to return immediately to the user while running the long computation asynchronously.
I understand the most robust way to do this would be to use a message broker in the architecture, but I was wondering if there is a simpler way to do it.
I tried the Executor plugin but that blocks the http request from returning until the long computation is done.
I tried the Quartz plugin, but that seems to be good for periodic tasks (unless there is a way to run a job just once?)
How are you guys handling such requests in Grails?
Where do you want to process veryLongComputation(), on the same Grails server, or a different server?
If the same server, you don't need JMS, another option is to just create a new thread and process the computation asynchronously.
def index = {
def asyncProcess = new Thread({
someVeryLongComputation()
} as Runnable )
asyncProcess.start()
render "Long computation was launched."
}
If you use a simple trigger in Grails Quartz and set the repeatCount to 0, the job will only run once. It runs separate from user requests, however, so you'd need to figure out some way to communicate to user when it completed.
I know this is a very old question, just wanted to give an updated answer.
Since grails 2.3, the framework supports async calls using Servlet 3.0 async request handling (of course, a servlet 3.0 container must be used and the servlet version should be 3.0 in the configuration, which it is per default)
It is documented here : http://grails.org/doc/latest/guide/async.html
In general, there are two ways achieving what you asked for:
import static grails.async.Promises.*
def index() {
tasks books: Book.async.list(),
totalBooks: Book.async.count(),
otherValue: {
// do hard work
}
}
or the Servlet Async way:
def index() {
def ctx = startAsync()
ctx.start {
new Book(title:"The Stand").save()
render template:"books", model:[books:Book.list()]
ctx.complete()
}
}
Small note - The grails method is using promises, which is a major (async) leap forward. Any Promise can be chained to further promised, have a callback on success and fail etc'
Have you tried Grails Promisses API? It should be as simple as
import static grails.async.Promise
import static grails.async.Promises
class FooController {
def index = {
Promise p = Promises.task {
someVeryLongCompution() //e.g crawl a set of web pages
}
render "Long computation was launched."
}
}
Try Spring events plugin - It supports asynchronous event listeners.
If you'd like to use the Quartz plugin (as we always do), you can do it like this. It works well for us:
DEFINE A JOB (with no timed triggers)
static triggers = {
simple name:'simpleTrigger', startDelay:0, repeatInterval: 0, repeatCount: 0
}
CALL <job>.triggerNow() to manually execute the job in asynchronous mode.
MyJob.triggerNow([key1:value1, key2: value2]);
Pro Tip #1
To get the named parameters out the other side...
def execute(context) {
def value1 = context.mergedJobDataMap.get('key1');
def value2 = context.mergedJobDataMap.get('key2');
...
if (value1 && value2) {
// This was called by triggerNow(). We know this because we received the parameters.
} else {
// This was called when the application started up. There are no parameters.
}
}
Pro Tip #2
The execute method always gets called just as the application starts up, but the named parameters come through as null.
Documentation: http://grails.org/version/Quartz%20plugin/24#Dynamic%20Jobs%20Scheduling
The best solution for this kind of problem is to use JMS, via the JMS plugin.
For a simpler implementation, that doesn't requires an externel server/service, you can try the Spring Events plugin.
Grails 2.2.1 Solution I had an additional requirement that said the report had to auto pop a window when it was complete. So I chose the servlet way from above with a twist. I replaced the render a view with a json formatted string return it looked like this.
Additionally my client side is not a gsp view, it is ExtJS 4.1.1 (a HTML5 product)
enter code here
def index() {
def ctx = startAsync()
ctx.start ({
Map retVar = [reportId: reportId, success: success];
String jsonString = retVar as JSON;
log.info("generateTwoDateParamReport before the render out String is: " + jsonString);
ctx.getOriginalWebRequest().getCurrentResponse().setContentType("text/html");
ctx.getOriginalWebRequest().getCurrentResponse().setCharacterEncoding("UTF-8");
log.info("current contentType is: "ctx.getOriginalWebRequest().getCurrentResponse().contentType);
try {
ctx.getOriginalWebRequest().getCurrentResponse().getWriter().write(jsonString);
ctx.getOriginalWebRequest().getCurrentResponse().getWriter().flush();
ctx.getOriginalWebRequest().getCurrentResponse().setStatus(HttpServletResponse.SC_OK);
}
catch (IOException ioe)
{
log.error("generateTwoDateParamReport flush data to client failed.");
}
ctx.complete();
log.info("generateNoUserParamsReport after complete");
});
}
I have some questions with a particular structure of a program I'm writing.
I'm using a Remote Object to make a remote call to a Rails method (using WebOrb). The problem arises in the way that I get my data back.
Basically I have a function, getConditions, in which I add an event listener to my remote call and then I make the remote call. However, what I want to do is to get that data back in getConditions so I can return it. This is a problem because I only access the event result data in the event handler. Here's some basic code describing this issue:
public function getConditions():Array
{
remoteObject.getConditions.addEventListener("result", onConditionResult);
remoteObject.getConditions();
//Here is where I want to get my event.result data back
}
public function onConditionResult(event:ResultEvent):void
{
//Here's the data that I want
event.result;
}
How can I achieve this data turn-about?
Remote calls in flex are always asynchronous so you won't be able to call getConditions() and wait there for the result. You have to use a function closure to process the results, either by means of an event handler than you declare elsewhere or a dynamic one created immediately within getConditions(), like so:
remoteObject.getConditions.addEventListener("result", function(event:ResultEvent):void {
// Run the code that you would want to when process the result.
});
remoteObject.getConditions();
The advantage of doing the above is that you would be able to "see" parameters passed to getConditions() or the result of any logic that happened before addEventListener() in the function closure. This however, takes a slight performance hit compared to declaring an explicit function (for that exact reason).
I should also add that doing so requires you to clean up after yourselves to make sure that you are not creating a new listener for every request.
you do it like this
public function getConditions():Array
{
remoteObject.getConditions.addEventListener("result", onConditionResult);
remoteObject.getConditions();
}
public function callMyExtraFunction(data:Object):void
{
//Here is where you want to get your event.result data back
}
public function onConditionResult(event:ResultEvent):void
{
//Here's the data that you want
var data:Object = event.result;
callMyExtraFunction(data);
}
You could make use of Call Responder like so :
<s:CallResponder id="getOperationsResult"/>
then use these lines to get the result from get operations
getOperationResult.token = remoteObject.getOperation();
this creates the call and returns the result stores it in getOpresult
whnever u want to access this u can call that token or getOperationResult.lastResult
Hope that helps
Chris