Apex Interview Questions Answers And Tutorial

266. What is apex scheduler?

Apex scheduler is used to invoke Apex classes to run at specific times, first implement the Schedulable interface for the class, then specify the schedule using either the Schedule Apex page in the Salesforce user interface, or the System.schedule method.

The Schedulable interface contains one method that must be implemented, execute.

global void execute(SchedulableContext sc){}

The implemented method must be declared as global or public.

The following example implements the Schedulable interface for a class called mergeNumbers:

global class scheduledMerge implements Schedulable{

global void execute(SchedulableContext SC) {

mergeNumbers M = new mergeNumbers();

   }

}

The following example uses the System.Schedule method to implement the above class.

scheduledMerge m = new scheduledMerge();

        String sch = '20 30 8 10 2 ?';

system.schedule('Merge Job', sch, m);

You can also use the Schedulable interface with batch Apex classes. The following example implements the Schedulable interface for a batch Apex class called batchable:

global class scheduledBatchable implements Schedulable{

global void execute(SchedulableContext sc) {

batchable b = new batchable();

database.executebatch(b);

   }

}

Use the SchedulableContext object to keep track of the scheduled job once it's scheduled. The SchedulableContext method getTriggerID returns the ID of the CronTrigger object associated with this scheduled job as a string. Use this method to track the progress of the scheduled job.

To stop execution of a job that was scheduled, use the System.abortJob method with the ID returned by the.getTriggerID method.

267. Write a syntax and structure of scheduler class?

Sample class

global class ScheduleDemo implements Schedulable{

            global void execute(SchedulableContext sc){

                        BatchClass b = new BatchClass();

                        database.executeBatch(b);

}

}

268. What is Scheduler class in Apex?

The Apex class which is programmed to run at pre defined interval.

Class must implement schedulable interface and it contains method named execute().

There are two ways to invoke scheduler:

1.     Using UI

2.     Using System.schedule (Schedule method of System class)

The classes which implements interface schedulable get the button texted with “Schedule”, when user clicks on that button; new interface opens to schedule the classes which implements that interface.

To see what happened to scheduled job, go to “Monitoring | Scheduled jobs “

Example of scheduling:

scheduledMerge m = new scheduledMerge();

String sch = '20 30 8 10 2 ?';

system.schedule('Merge Job', sch, m);

Here:

20 represents seconds

30 represents minutes

8 represents hour of the day

10 represents 10^th day of month

2 represents month of the year

? represents day of the month

269. Write a apex code to send a email?

Sample code snippet to send an email using apex code

Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();

String[] toAddresses = new String[]{‘talk2srikrishna@gmail.com’};

mail.setToAddress(toAddresses);

mail.setSubject(‘Sample Mail Subject’);

mail.setPlainTextBody(‘Hello World!’);

Messaging.sendEmail(new Messaging.SingleEmailMessage[]{mail});

270. What are the aggregate functions supported by salesforce SOQL?

Following aggregate functions are supported by salesforce SOQL

1.     SUM()

2.     MIN()

3.     MAX()

4.     COUNT()

5.     AVG()

6.     COUNT_DISTINCT()

271. Write a sample aggregate query or explain how to write a aggregate queries?

The return types of Aggregate functions are always an array of AggregateResult.

Sample Code

AggregateResult[] ar = [select AVG(Amount) aver from Opportunity];

Object avgAmt = ar[0].get(‘aver’);

272. Write a code to find the average Amount for all your opportunities by campaign?

AggregateResult[] arList = [select CampaignId, AVG(amount) from Opportunity group by CampaignId];

for(AggregateResult ar : arList){

            System.debug(‘CampaignId ’ + ar.get(‘CampaignId’));

            System.debug(‘Average Amount’ + ar.get(‘expr0’));

}

273. What are email services in salesforce and explain how we can use them in code?

Email services are automated processes that use apex class to process the contents, headers and attachment of an inbound email.

Sample code

Use Case: create a contact record if the inbound email subject is Create Contact and body contains contact name

global CreateContactFromEmail implements Messaging.InboundEmailHandler{

global Messaging.InboundEmailResult handleInboundEmail(Messaging.InboundEmail email, Messaging.InboundEnvelop envelop){

            Messaging.InboundEmailResult res = new Messaging.InboundEmailResult();

            String strToCompare = ‘Create Contact’;

            If(email.subject.equalsIgnoreCase(strToCompare)){

                        Contact c = new Contact();

                        c.LastName = email.plainTextBody();

                        insert c;

                       

                        //save text attachments

for(Messaging.InboundEmail.TextAttachment att : email.textAttachments){

            Attachment a = new Attachment();

            a.Name = att.fileName;

            a.Body = att.Blob.valueOf(att.Body);

            a.ParentId = c.Id;

            insert attachment;

}

                       

//save binary attachments

for (Messaging.Inboundemail.BinaryAttachment bAttachment : email.binaryAttachments) {

            Attachment attachment = new Attachment();

            attachment.Name = bAttachment.fileName;

            attachment.Body = bAttachment.body;

            attachment.ParentId = c.Id;

insert attachment;

}

}

res.Success = true;

return res;

}

}

274. What is the row limit for apex:dataTable and apex:pageBlockTable?

The data set for both apex:dataTable and apex:pageBlockTable can have up to 1000 items.

275. What is the difference between apex:pageMessages, apex:pageMessage, apex:Message and apex:Messages?

apex:PageMessages:

This component displays all messages that were generated for all components on the current page, presented using the salesforce styling. This will display both salesforce generated messages as well as custom messages added to the ApexPages class 

apex:PageMessage:

Apex:PageMessage is a component that adds single message on the page. This is used to display custom message using the salesforce formatting

apex:Message:

apex:Message is used to display an error on only a specific field. It is used to allow developers to place field specific errors in specific location.

apex:Messages:

apex:Messages is similar to apex:Message but it displays all errors

276. How can we hard delete a record using a Apex class/by code?

ALL ROWS key word can be used to get all the records including records in the recycle bin.

Below is the sample code to delete contact records from recycle bin

List<Contact> dContactList=[Select ID From Contact Where IsDeleted = true limit 199 ALL ROWS];
Database.emptyRecycleBin( dContactList );

278. Write a syntax and structure of batch class?

Sample class

global Class BatchDemo implements Database.Batchable<sObject>{

global Database.QueryLocator start(Database.BatchableContext bc){

            return Database.getQueryLocator(query);

}

global void execute(Database.BachableContext bc, List<sObjects> scope){

           

}

global void finish(Database.BachableContext bc){

                       

}

}

Below code will call the batch class

BatchDemo bd = new BatchDemo();

database.executebatch(bd);

279. What is batch apex?

Batch Apex is exposed as an interface that must be implemented by the developer. Batch jobs can be programmatically invoked at runtime using Apex.

Need of Batch Apex: - As you all might know about the salesforce governor limits on its data. When you want to fetch thousands of records or fire DML on thousands of rows on objects it is very complex in salesforce and it does not allow you to operate on more than certain number of records which satisfies the Governor limits.

But for medium to large enterprises, it is essential to manage thousands of records every day. Adding/editing/deleting them when needed.

Salesforce has come up with a powerful concept called Batch Apex. Batch Apex allows you to handle more number of records and manipulate them by using a specific syntax.

We have to create a global apex class which extends Database.Batchable Interface because of which the salesforce compiler will know, this class incorporates batch jobs. Below is a sample class which is designed to delete all the records of Account object (Lets say your organization contains more than 50 thousand records and you want to mass delete all of them).

Examples:-

global class deleteAccounts implements Database.Batchable

{

global final String Query;

global deleteAccounts(String q)

{

Query=q;

}

global Database.QueryLocator start(Database.BatchableContext BC)

{

return Database.getQueryLocator(query);

}

global void execute(Database.BatchableContext BC,List scope)

{

List <Account> lstAccount = new list<Account>();

for(Sobject s : scope)

{

 Account a = (Account)s;

lstAccount.add(a);

}

Delete lstAccount;

}

global void finish(Database.BatchableContext BC)

{

                //Send an email to the User after your batch completes

                Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();

String[] toAddresses = new String[] {‘sforce2009@gmail.com’};

mail.setToAddresses(toAddresses);

mail.setSubject('Apex Batch Job is done‘);

mail.setPlainTextBody('The batch Apex job processed ');

Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });

}

}

//This is how the batch class is called.

id batchinstanceid = database.executeBatch(new deleteAccounts(‘select Id from Account’));

280. What are web service callouts?

Apex Code supports the ability to expose Apex methods as a Web service. Apex also supports the ability to invoke external web services and this will refer to as 'Callouts.' The former is involved in creating a web service that a client can invoke, while the latter is invoking an external web service.

281. What are wrapper classes?

A wrapper or container class is a class, a data structure, or an abstract data type whose instances are collections of other objects.

282. How do you hide header and sidebar on visualforce page?

Below is the code to hide sidebar and header

<apex:page showHeader="false" sidebar="false">

</apex:page>

283. What is the difference between standard and custom controller?

The standard controller is auto generated by SF for all objects.

Custom controllers are written by you and do what your code tells them to do.

284. How do you read parameter in visualforce page?

Below syntax can be used to read parameters in visualforce page

<apex:inputField value="{!$CurrentPage.parameters.Paramtervalue}"/>

Additional code:

If you're writing a custom controller, use the ApexPages global object variable and currentPage() and getParameters() methods to get query string parameters. For example, to get the value of the name query parameter in the URL: https://na1.salesforce.com/001/e?name=value, use the following line in your custom controller:

String value = ApexPages.currentPage().getParameters().get('name');

·If you're editing a page, use the $PageContext global variable in a merge field.

For example, suppose you want to add the Open Activities related list to an account detail page, but instead of showing the account's activities, you want to show the activities of a specified contact. To specify the contact, the following page looks for a query string parameter for the contact's ID under the name relatedId:

<apex:page standardController="Account">

<apex:pageBlock title="Hello {!$User.FirstName}!">

        You belong to the {!account.name} account.<br/>

        You're also a nice person.

</apex:pageBlock>

<apex:detail subject="{!account}" relatedList="false"/>

<apex:relatedList list="OpenActivities"

                   subject="{!$CurrentPage.parameters.relatedId}"/>

</apex:page>

For this related list to render in a saved page, valid account and contact IDs must be specified in the URL. For example, if 001D000000HRgU6 is the account ID and 003D000000OXDIx is the contact ID, use the URLhttps://na3.salesforce.com/apex/MyFirstPage?id=001D000000HRgU6& relatedId=003D000000OXDIx.

To set a query string parameter:

·       If you're writing a custom controller, use the setParameters() method with ApexPages.currentPage() to add a query parameter in a test method. For example:

String key = 'name';

String value = 'Caroline';

ApexPages.currentPage().setParameters().put(key, value);

Note

The setParameters() method is only valid inside test methods.

·       If you're editing a page, you can either construct a URL manually:

<apex:outputLink value="http://google.com/search?q={!account.name}">

    Search Google

</apex:outputLink>

Or you can use the <apex:param> tag as a child tag to write cleaner code:

<apex:outputLink value="http://google.com/search">

    Search Google

<apex:param name="q" value="{!account.name}"/>

</apex:outputLink>

285. How can we pass javascript variable to apex class?

VF Page (Use assign input variable to VF using $Component.FieldId)

<apex:page controller="Js_Test_Class">

<apex:form>

<script>

            function setVal()

            {

            document.getElementById("{!$Component.hdnField}").value = "TestValue";

            }

</script>

<apex:inputHidden id="hdnField" value="{!theValue}" />

<apex:commandButton value="Post Page" action="{!post}" />

</apex:form>

<script>

setVal();

</script>

</apex:page>

Controller (Declare setter and getter for the variable being used in VF page)

public class Js_Test_Class {

            public String theValue { get;set;}

public void post() {

System.Debug('The value is : ' + theValue);

    }

}

286. Is it possible to call apex method in javascript code? If yes, explain?

Yes, we can call apex methods using javascript. We can achieve this using ActionFunction. ActionFunction allow you to tie an apex method to a javascript function name and invoke synchronously. ActionFunction must be a child of apex:form component.

Example VF Page

<apex:page controller="t">

<script>

function myJavascriptFunc()

    {

alert('Entered Javascript') ;

CallApexMethod() ;

    }

</script>

<apex:form >

<apex:actionFunction name="CallApexMethod" action="{!myActionInController}" onComplete="alert('After apex method') ;"/>

<apex:pageBlock >

<apex:pageBlockButtons>

<apex:commandButton value="Hit Me" onclick="myJavascriptFunc() ;"/>

</apex:pageBlockButtons>

</apex:pageBlock>

</apex:form>

</apex:page>

Example Controller

public class t

public PageReference myActionInController(){

return null ;

    }

}

287. What is commandLink? Explain the usage?

CommandLink is a link that executes an action defined by a controller, and then refreshes the current page or navigate to the different page based on the PageReference variable that is returned by the action.

commandLink component must be a child of an form component.

Example:

<apex:commandLink action=”{!save}” value=”Save” id=”theCommandLink”/>

288. What is outputLink? Explain the usage?

OutputLink is a link to URL. This component is rendered in HTML as an anchor tag with an href attribute. The body of the OutputLink is a text or image that displays as the link

Example:

<apex:outputLink value=”http://www.google.com” id=”theLink”>www.google.com</outputLink>

289. How to get URL parameters in Visuaforce page?

If the URL is something link this

https://<salesforce instance>/apex/getQueryStringParam?id=001d000000B1Gj5&cid=003d000000BIjFh

and if we want to read cid in our visualforce page then,

Use: $CurrentPage.parameters.cid

Or

If there is a single parameter in the URL string link this

https://xxx.visual.force.com/apex/NewPage?TestValue=value1&retURL=a0HS000000450UD

Then Use:

$CurrentPage.parameters.Paramtervalue

290. How to set URL parameters in Visuaforce page?

Setting a Query String parameter can be achieved by two ways.

One:

Construct a URL manually like,

<apex:outputLink value="http://google.com/search?q={!account.name}">

    Search Google

</apex:outputLink>

Two

<apex:outputLink value="http://google.com/search">

    Search Google

<apex:param name="q" value="{!account.name}"/>

</apex:outputLink>

291. How to get URL parameters in APEX class?

If the URL is something link this

https://<salesforce instance>/apex/getQueryStringParam?id=001d000000B1Gj5&cid=003d000000BIjFh

And if we want to read cid in our visualforce page then,

Use:

String id = ApexPages.currentPage().getParameters().get('id');

String id = ApexPages.currentPage().getParameters().get('cid');

292. How to set URL parameters in APEX class?

To set a URL parameter using Apex code use below syntax

String key = 'name';

String value = 'Caroline';

ApexPages.currentPage().getParameters().put(key, value);

Or

ApexPages.currentPage().getParameters().set(‘value’);

293. Explain how MVC architecture fit for Salesforce?

In salesforce, Apex Classes works as Controllers, Visualforce Pages works as View and Custom objects works as Model.

294. How to use actionFunction, actionSupport and actionPollar in salesforce?

actionFunction : provides support for invoking controller action methods directly from JavaScript code using an AJAXrequest

Used when we need to perform similar action on various events. Even though, you can use it in place of actionSupport as well where only event is related to only one control.

Example:

actionFunction: provides support for invoking controller action methods directly from JavaScript code using an AJAXrequest

Example :

<!-- Page: -->

<apex:page controller="exampleCon">

<apex:form>

<!-- Define the JavaScript function sayHello-->

<apex:actionFunction name="sayHello" action="{!sayHello}" rerender="out"

status="myStatus"/>

</apex:form>

<apex:outputPanel id="out">

<apex:outputText value="Hello "/>

<apex:actionStatus startText="requesting..." id="myStatus">

<apex:facet name="stop">{!username}</apex:facet>

</apex:actionStatus>

</apex:outputPanel>

<!-- Call the sayHello JavaScript function using a script element-->

<script>window.setTimeout(sayHello,2000)</script>

<p><apex:outputText value="Clicked? {!state}" id="showstate" /></p>

<!-- Add the onclick event listener to a panel. When clicked, the panel triggers

the methodOneInJavascript actionFunction with a param -->

<apex:outputPanel onclick="methodOneInJavascript('Yes!')" styleClass="btn">

Click Me

</apex:outputPanel>

<apex:form>

<apex:actionFunction action="{!methodOne}" name="methodOneInJavascript"

rerender="showstate">

<apex:param name="firstParam" assignTo="{!state}" value="" />

</apex:actionFunction>

</apex:form>

</apex:page>

/*** Controller ***/

public class exampleCon {

String uname;

public String getUsername() {

return uname;

}

public PageReference sayHello() {

uname = UserInfo.getName();

return null;

}

public void setState(String n) {

state = n;

}

public String getState() {

return state;

}

public PageReference methodOne() {

return null;

}

private String state = 'no';

}

ActionSupport: A component that adds AJAX support to another component, allowing the component to be refreshed asynchronously by the server when a particular event occurs, such as a button click or mouseover.

Used when we want to perform an action on a particular event of any control like onchange of any text box or picklist.

Example:

<!-- Page: -->

<apex:page controller="exampleCon">

<apex:form>

<apex:outputpanel id="counter">

<apex:outputText value="Click Me!: {!count}"/>

<apex:actionSupport event="onclick"

action="{!incrementCounter}"

rerender="counter" status="counterStatus"/>

</apex:outputpanel>

<apex:actionStatus id="counterStatus"

startText=" (incrementing...)"

stopText=" (done)"/>

</apex:form>

</apex:page>

/*** Controller: ***/

public class exampleCon {

Integer count = 0;

public PageReference incrementCounter() {

count++;

return null;

}

public Integer getCount() {

return count;

}

}

 ActionPolor: A timer that sends an AJAX update request to the server according to a time interval that you specify. The update request can then result in a full or partial page update. You should avoid using this component with enhanced lists.

Used when we want to perform an action on server again and again for a particular time interval. 

Example:

<!-- Page -->

<apex:page controller="exampleCon">

<apex:form>

<apex:outputText value="Watch this counter: {!count}" id="counter"/>

<apex:actionPoller action="{!incrementCounter}" rerender="counter" interval="15"/>

</apex:form>

</apex:page>

/*** Controller: ***/

public class exampleCon {

Integer count = 0;

public PageReference incrementCounter() {

count++;

return null;

}

295. What is the difference between actionFunction and actionSupport tags?

Sl No	ActionSupport	ActionFunction
1)	Directly call action method without javascript	Call action method from javascript with AJAX
2)	It can be used to call action method on  single event	It can be used to call action method on different event
3)	It cannot be called from javascript function. It only invoke controller action methods from other Visualforce components	It defines a new JavaScript function which can then be called from within a block of JavaScript code.

296. How do you do File Upload using visualforce?

Below is the code sample of file upload in visualforce

<!-- Upload a file and put it in your personal documents folder-->

<!-- Page: -->

<apex:page standardController="Document" extensions="documentExt">

<apex:messages />

<apex:form id="theForm">

<apex:pageBlock>

<apex:pageBlockSection>

<apex:inputFile value="{!document.body}" filename="{!document.name}"/>

<apex:commandButton value="Save" action="{!save}"/>

</apex:pageBlockSection>

</apex:pageBlock>

</apex:form>

</apex:page>

/*** Controller ***/

public class documentExt {

public documentExt(ApexPages.StandardController controller) {

        Document d = (Document) controller.getRecord();

        d.folderid = UserInfo.getUserId(); //this puts it in My Personal Documents

    }                

}

298. Explain Apex Data Types

Apex primitive data types include
• String
• Blob (for storing binary data)
• Boolean
• Date, DateTime and Time
• Integer, Long, Decimal, Double
• ID (Force.com database record identifier)

 Example:
• DateTime dt = System.now() + 1;
• Boolean isClosed = true;
• String sCapsFirstName = ‘Andrew’.toUpperCase();

Apex sObject Types
Sobject (object representing a Force.com standard or custom object)

Example:
• Account acct = new Account(); //Sobject example

Apex has the following types of collections
• Lists
• Maps
• Sets

Example:
• List myList = new List();
• myList.add(12); //Add the number 12 to the list
• myList.get(0); //Access to first integer stored in the List

Enums
• Enum (or enumerated list) is an abstract that stores one value of a finite set of specified identifiers.
• To define an Enum, use enum keyword in the variable declaration and then define the list of values.
• By creating this Enum, you have created a new data type called Season that can be used as any other data type.

Example:
• public enum Season {WINTER, SPRING, SUMMER, FALL}

299. Explain Apex Variables?

Local variables are declared with Java-style syntax.
For example:
• Integer i = 0;
• String str;
• Account a;
• Account[] accts;
• Set s;
• Map<ID, Account> m;

300. Explain Static Methods and Variables?

• Class methods and variables can be declared as static. Without this keyword, the default is to create instance methods and variables.
• Static methods are accessed through the class itself, not through an object of the class:

Example:
public class blogReaders {
public static boolean firstScript = false;
}
• Static methods are generally utility methods that do not depend on an instance. System methods are static.
• Use static variables to store data that is shared with in the class.
• All instances of the same class share a single copy of static variables.
• This can be a technique used for setting flags to prevent recursive