Streaming APIs - Easy Code

Streaming API is useful when you want notifications to be pushed from the server to the client based on criteria that you define.

The sequence of events when using Streaming API is as follows: (explained in detail later)
1. Create a PushTopic based on a SOQL query. This defines the channel.
2. Clients subscribe to the channel.
3. A record is created or updated (an event occurs). The changes to that record are evaluated.
4. If the record changes match the criteria of the PushTopic query, a notification is generated by the server and received by the subscribed clients.

Before we get started, I recommend you to go through these topics:

1) Push Technology
2) Bayeux Protocol, CometD, and Long Polling


We will achieve this once we are done with all steps (given below):

Now follow these steps:

Prerequisites:
1) The “Streaming API” permission must be enabled -> "Your Name > Setup > Customize > User Interface"
2) The logged-in user must have “Read” permission on the PushTopic standard object to receive notifications.
3) The logged-in user must have “Create” permission on the PushTopic standard object to create and manage PushTopic records.
4) The logged-in user must have “Author Apex” permissions to create a PushTopic by using the Developer Console.


Step 1: Create an Object - In our case we will use Account

Step 2: Create a PushTopic
Use the Developer Console to create the PushTopic record. You can use either Developer Console or Workbench. If needed these records can be updated.

"Your Name > Developer Console"

PushTopic pushTopic = new PushTopic();
pushTopic.Name = 'RefreshAccounts';
pushTopic.Query = 'SELECT Id, Name FROM Account';
pushTopic.ApiVersion = 26.0;
pushTopic.NotifyForOperations = 'All';
pushTopic.NotifyForFields = 'Referenced';
insert pushTopic;

Step 3: Create Static resource

1. Download the CometD compressed archive (.tgz) file from http://download.cometd.org/cometd-2.2.0-distribution.tar.gz
2. Extract the following JavaScript files from cometd-2.2.0-distribution.tar.gz:
• cometd-2.2.0/cometd-javascript/common/target/org/cometd.js
• cometd-2.2.0/cometd-javascript/jquery/src/main/webapp/jquery/jquery-1.5.1.js
• cometd-2.2.0/cometd-javascript/jquery/src/main/webapp/jquery/json2.js
• cometd-2.2.0/cometd-javascript/jquery/src/main/webapp/jquery/jquery.cometd.js

File Name	Static Resource Name
cometd.js	Cometd
jquery-1.5.1.js	Jquery
json2.js	json2
jquery.cometd.js	jquery_cometd

Step 4: Test the PushTopic Channel

Here is the code sample

Visualforce Page

<apex:page id="PG" controller="StreamingAPIController">
<apex:form id="FRM">

    <apex:includeScript value="{!$Resource.cometd}"/>
    <apex:includeScript value="{!$Resource.jquery}"/>
    <apex:includeScript value="{!$Resource.json2}"/>
    <apex:includeScript value="{!$Resource.jquery_cometd}"/>

    <apex:actionFunction name="GetRefreshedAccounts" reRender="PB,PBT"/>

    <script type="text/javascript">
        (function($)
        {
            $(document).ready(function() {
                
                // Connect to the CometD endpoint
                $.cometd.init({
                    url: window.location.protocol+'//'+window.location.hostname+'/cometd/24.0/',
                    requestHeaders: { Authorization: 'OAuth {!$Api.Session_ID}'}
                });
                
                // Subscribe to a topic. JSON-encoded update will be returned in the callback
                // In this example we are using this only to track the generated event
                $.cometd.subscribe('/topic/RefreshAccounts', function(message)
                {
                    //You can use message as it will return you many attributes
                    //I am just using to track that event is generated
                    GetRefreshedAccounts();
                });

            });
        })(jQuery)
    </script>

    <apex:pageBlock id="PB">
        <apex:variable var="count" value="{!0}" />
        <apex:pageBlockTable id="PBT" value="{!getRefreshedAccount}" var="AllAcc">
            
            <apex:column headerValue="S.No.">
                <apex:variable var="count" value="{!count+1}" />
                {!count}
            </apex:column>
            <apex:column value="{!AllAcc.Name}" headerValue="Name"/>
            
        </apex:pageBlockTable>
    </apex:pageBlock>

</apex:form>
</apex:page>

Apex Class

public class StreamingAPIController
{
    //Everytime page is reRendered it will get refreshed values of account
    public List<Account> getRefreshedAccount
    {
        get
        {
            return [select Id, Name from Account LIMIT 50000] ;
        }
        set;
    }
    
    public StreamingAPIController()
    {
    }
}

This is very small and simple sample code, you can do a lot more with streaming APIs. Please refer these documents to learn more:

1) http://www.salesforce.com/us/developer/docs/api_streaming/api_streaming.pdf
2) http://www.salesforce.com/us/developer/docs/api_streaming/index.htm
3)http://wiki.developerforce.com/page/Getting_Started_with_the_Force.com_Streaming_API

Uploading Multiple Attachments into Salesforce - Simple Code

Okay, so here is the simple code to upload multiple attachments into Salesforce. Please note that I've used standard controller ("Account" in the code) so you need to pass the record Id in parameter. You can also change this according to your need as code is dynamic.

So first option allow you to select how many files you want to upload. Say, you have selected "5", then it will give you 5 options to select files and once you click on "Upload" it will upload the files as attachments to the associated record.

Visualforce Page Code:

<apex:page standardController="Account" extensions="MultipleUploadController">
    <apex:form>
        <apex:pageBlock title="Upload Multiple Attachment to Object">
            
            <apex:pageBlockButtons>
                <apex:commandButton value="Upload"  action="{!SaveAttachments}"/>
            </apex:pageBlockButtons>
            
            <apex:pageMessages id="MSG"/>
            <apex:actionFunction name="ChangeCount" action="{!ChangeCount}"/>
            
            <apex:pageblocksection>
                            
                <apex:pageBlockSectionItem>
                    <apex:outputLabel value="How many files you want to upload?"/>
                    <apex:selectList onchange="ChangeCount() ;" multiselect="false" size="1" value="{!FileCount}">
                        <apex:selectOption itemLabel="--None--" itemValue=""/>
                        <apex:selectOptions value="{!filesCountList}"/>
                    </apex:selectList>
                </apex:pageBlockSectionItem>
            
            </apex:pageblocksection>
            
            <apex:pageBlockSection title="Select Files" rendered="{!IF(FileCount != null && FileCount != '', true , false)}">
                <apex:repeat value="{!allFileList}" var="AFL">
                    <apex:inputfile value="{!AFL.body}" filename="{!AFL.Name}" />
                    <br/>
                </apex:repeat>
            </apex:pageBlockSection>
            
        </apex:pageBlock>
    </apex:form>
</apex:page>

Apex Code:

public class MultipleUploadController
{   
    //Picklist of tnteger values to hold file count
    public List<SelectOption> filesCountList {get; set;}
    //Selected count
    public String FileCount {get; set;}
    
    public List<Attachment> allFileList {get; set;}
    
    public MultipleUploadController(ApexPages.StandardController controller)
    {
        //Initialize  
        filesCountList = new List<SelectOption>() ;
        FileCount = '' ;
        allFileList = new List<Attachment>() ;
        
        //Adding values count list - you can change this according to your need
        for(Integer i = 1 ; i < 11 ; i++)
            filesCountList.add(new SelectOption(''+i , ''+i)) ;
    }
    
    public Pagereference SaveAttachments()
    {
        String accId = System.currentPagereference().getParameters().get('id');
        if(accId == null || accId == '')
            ApexPages.addmessage(new ApexPages.message(ApexPages.Severity.ERROR,'No record is associated. Please pass record Id in parameter.'));
        if(FileCount == null || FileCount == '')
            ApexPages.addmessage(new ApexPages.message(ApexPages.Severity.ERROR,'Please select how many files you want to upload.'));

        List<Attachment> listToInsert = new List<Attachment>() ;
        
        //Attachment a = new Attachment(parentId = accid, name=myfile.name, body = myfile.body);
        for(Attachment a: allFileList)
        {
            if(a.name != '' && a.name != '' && a.body != null)
                listToInsert.add(new Attachment(parentId = accId, name = a.name, body = a.body)) ;
        }
        
        //Inserting attachments
        if(listToInsert.size() > 0)
        {
            insert listToInsert ;
            ApexPages.addmessage(new ApexPages.message(ApexPages.Severity.INFO, listToInsert.size() + ' file(s) are uploaded successfully'));
            FileCount = '' ;
        }
        else
            ApexPages.addmessage(new ApexPages.message(ApexPages.Severity.ERROR,'Please select at-least one file'));
            
        return null;
    }
    
    public PageReference ChangeCount()
    {
        allFileList.clear() ;
        //Adding multiple attachments instance
        for(Integer i = 1 ; i <= Integer.valueOf(FileCount) ; i++)
            allFileList.add(new Attachment()) ;
        return null ;
    }
}

You can enhance the code if you like, as I've provided the basic code which is re-usable. Also you can change the object passed in standard controller and code will handle the rest. URL should have ID else you will get error on UI :-)

Say, I've saved my VFP code as "MultipleUpload", so my URL will be https://...../apex/MultipleUpload?id=XXXXXXXXXXXXXXX (account id in this code).

Happy Coding.

Reading Visualforce Page Code In Apex

Recently faced a strange requirement to change the Visualforce page code dynamically (apologies can't disclose the complete scenario)

So would like to share the small POC with code. Code will take Visualforce Page name as parameter and will return you the code written for that VFP as text. For example, this is my Visualforce Page saved with name "VisualforceCode"

<apex:page id="PG" controller="VisualforceCodeController">
<apex:form id="FRM">
    <apex:pageMessages id="PM"/>
    <apex:pageBlock id="PB">
        
        <apex:commandLink value="See Magic" action="{!DisplayCode}" >
            <apex:param assignTo="{!CurrentPageName}" value="{!$CurrentPage.Name}"/>
        </apex:commandLink>
        
        <br/> <br/>

        <apex:outputPanel id="OPT" rendered="{!showCodeSection}">
            <apex:outputLabel value="{!PageText}"/>
        </apex:outputPanel>
    
    </apex:pageBlock>
</apex:form>
</apex:page>

Now I want to read the code written in this page, so here is the working code which send page name as parameter in "UtilClass" to get the code as text:

public class VisualforceCodeController
{
    //To display section which hold code as text of VF page
    public boolean showCodeSection {get; set;}
    
    //To hold VF Code as text
    public String PageText {get; set;}
    
    //Hold current page name
    public String CurrentPageName {get; set;}
    
    public VisualforceCodeController()
    {
        CurrentPageName = '' ;
        showCodeSection = false ;
    }
    
    public PageReference DisplayCode()
    {
        if(CurrentPageName != '')
        {
            //Fetching VF code
            PageText = UtilClass.VFPageCode(CurrentPageName) ;
            showCodeSection = true ;
        }
        return null ;
    }
}

To get the visualforce page name I've used "{!$CurrentPage.Name}" which is a global variable

Here Util Class code:

//General Class with static methods
public class UtilClass
{
    //Method will take visualforce page name as parameter and returns the code written in it
    public static String VFPageCode(String PageName)
    {
        ApexPage testPage = new ApexPage();
        String PageText = '' ;
        
        if(PageName != '')
        {
            //Fetching visualforce page code
            testPage = [Select Id, Markup from ApexPage where name =: PageName];
            PageText = testPage.markup ;
        }
        return PageText ;
    }
}

There are many other methods you can use with "ApexPage" mentioned here. So if you want to update the VFP code from apex dynamically you can use "ApexPage"