[SalesForce] How to perform equivalent of an AJAX long-poll with Visualforce

I have a web page that communicates with a node.js backend. I use AJAX to long-poll the server, allowing realtime updates to be received as they occur server-side.

Below is a simplification of my existing client-side code. What I'd like to know is whether there's an equivalent way of doing this with Visualforce/Apex, or can I even host my existing code somehow within an apex page? Any hints, examples or walkthroughs would be more than welcome – I have only been using the Force platform for 3 days so I am still extremely unfamiliar with the technology, terminology, etc.

Also, the data I'm polling for is not Salesforce related, so I don't think the Streaming API will work because the whole topic/query concept is not applicable in this situation.

function poll() {

    longPollRequest = $.ajax({
        url: "http://myserver.com/longPoll",
        type: "GET",
        dataType: "jsonp",
        jsonpCallback: "localJsonpCallback",
        complete: function(jqXHR, textStatus ) {  
            poll(); // restart the poll
        },
        error: function (jqXHR, textStatus, errorThrown) {  }
    });
}

function localJsonpCallback(json) {
    // parse long-poll response
}

Best Answer

Take a look at the Streaming API. You can have your VF page subscribe to a topic and get near real time updates. This blog post does a really good job walking you through setting it up on your page.

Related Solutions

[SalesForce] Visualforce: Major grief with IE9 AJAX refresh/rerender issues

Actually I found the solution finally.

Thanks to this guy's post in the developer forums. http://boards.developerforce.com/t5/Visualforce-Development/actionFunction-causing-Javascript-error-when-using-oncomplete-or/m-p/193724#M25961

The key was to override the Javascript function in question and add a try/catch block to ensure IE does not terminate the running code.

A4J.AJAX.XMLHttpRequest.prototype._copyAttribute = function (src, dst, attr) {
var value = src.getAttribute(attr);
if (value) {
    try {
        dst.setAttribute(attr, value);
    } catch (err) {
        //alert('Error with Salesforce: ' + err.description + '\nattr: ' + attr + '\n');
    }
}

};

I hope this helps someone who runs into this same issue with IE9.

[SalesForce] jQuery AJAX request responses with 401 Unauthorized

Well, I didn't manage to use cross-domain AJAX request, but for AJAX request to Apex class I used call to RemoteAction. Here is frontend code:

<apex:page sidebar="false" standardController="Warehouse__c" extensions="WarehouseUtils">
<apex:includeScript value="{!URLFOR($Resource.jquery_and_css, '/js/jquery-1.7.2.min.js')}"  />
    <div>
        <input name="getList" value="Get warehouse list" type="button" onclick="getWarehouseList('Vilnius','54.68','25.28')" />
    </div>
    <div id="warehouseList">
    </div>
    <script type="text/javascript">
        var $j = jQuery.noConflict();
        $j(document).ready(function() {
            console.log($j().jquery);
        });
        function getWarehouseList(title, lat, lon) {
            WarehouseUtils.getAllWarehousesAndAdd(title, lat, lon, function(responseData, event){
                if(event.status) {
                    console.log(responseData);
                    var sTable = "<table>";
                    $j.each(responseData, function(index, item) {
                        sTable += "<tr>" + 
                                      "<td>" + item.Name + "</td>" + 
                                      "<td>" + item.Location__Latitude__s + "</td>" + 
                                      "<td>" + item.Location__Longitude__s + "</td>" + 
                                  "</tr>";
                    });
                    sTable += "</table>";
                    $j('#warehouseList').html(sTable);
                }
            });
        }
    </script>
</apex:page>

And backend:

global with sharing class WarehouseUtils {

    public WarehouseUtils(ApexPages.StandardController controller) {
    }

    @RemoteAction
    global static List<Warehouse__c> getAllWarehousesAndAdd(String pname, Decimal lat, Decimal lon) {
        String query = 'SELECT Id, Name, Location__Longitude__s, Location__Latitude__s, Street_Address__c, Phone__c, City__c ' + 
                       'FROM Warehouse__c ';
        List<Warehouse__c> warehouses = database.Query(query);
        Warehouse__c warehouse = new Warehouse__c(Name = pname, Location__Latitude__s = lat, Location__Longitude__s = lon);
        warehouses.add(warehouse);
        return warehouses;           
    }
}

Related Topic