Apex and Visual Force Page in Salesforce Interview Questions Answers

301. What is the use of static variable?

When you declare a method or variable as static, it’s initialized only once when a class is loaded. Static variables aren’t trmitted as part of the view state for a Visualforce page.
Static variables are only static within the scope of the request. They are not static across the server, or across the entire organization.

302. Explain Final variables?

• The final keyword can only used with variables.
• Classes and methods are final by default.
• Final variables can only be assigned a value once.
• When defining constants, both static and final keywords should be used.

Example: public static final Integer =47;

303. Difference between with sharing and without sharing in salesforce

By default, all Apex executes under the System user, ignoring all CRUD, field-level, and row-level security (that is always executes using the full permissions of the current user).

without sharing:
Enforcing the User’s Permissions, Sharing rules and field-level security should apply to the current user.
For example:
public with sharing class sharingClass {
// Code here
}

without sharing:
Not enforced the User’s Permissions, Sharing rules and field-level security.
For example:
public without sharing class noSharing {
// Code here
}

Enforcing the current user’s sharing rules can impact: (with sharing)
SOQL and SOSL queries – A query may return fewer rows than it would operating in system context.
DML operations – An operation may fail because the current user doesn’t have the correct permissions. For example, if the user specifies a foreign key value that exists in the organization, but which the current user does not have access to.

304. Explain Class Constructors with example?

• A constructor is a special method used to create (or instantiate) an object out of a class definition.
• Constructors never have explicit return types.
• Constructors have the same name as the class.
• Classes have default, no-argument, public constructor if no explicit constructors is defined.
• If you create a constructor that takes arguments and still want a no-argument constructor, you must explicitly define one.
• Constructors can be overloaded, meaning you can have multiple constructors with different parameters, unique argument lists, or signatures.
• Constructors are called before all other methods in the class.

For Example:
public class TestObject2 {
private static final Integer DEFAULT_SIZE = 10;
Integer size;
//Constructor with no arguments
public TestObject2() {
this(DEFAULT_SIZE); // Using this(…) calls the one argument constructor
}
// Constructor with one argument
public TestObject2(Integer ObjectSize) {
size = ObjectSize;
}
}
New objects of this type can be instantiated with the following code:
TestObject2 myObject1 = new TestObject2(42);
TestObject2 myObject2 = new TestObject2();

305. Class Access Modifiers

• Classes have different access levels depending on the keywords used in the class definition.

global: this class is accessible by all Apex everywhere.
• All methods/variables with the webService keyword must be global.
• All methods/variables dealing with email services must be global.
• All methods/variables/inner classes that are global must be within a global class to be accessible.

public: this class is visible across you application or name space.

private: this class is an inner class and is only accessible to the outer class, or is a test class.

protected: this me that the method or variable is visible to any inner classes in the defining Apex class. You can only use this access modifier for instance methods and member variables.

To use the private, protected, public, or global access modifiers, use the following syntax:
[(none)|private|protected|public|global] declaration

306. Explain Variable and Method Access Modifiers in Apex?

• Methods and variables have different levels depending on the keywords used in the declaration.
– private: This method/variable is accessible within the class it is defined.
– protected: This method/variable is also available to any inner classes or subclasses. It can only be used by instance methods and member variables.
– public: This method/variable can be used by any Apex in this application namespace.
– global: this method/variable is accessible by all Apex everywhere.
• All methods/variable with the webService keyword must be global.
– The default access modifier for methods and variables is private.

307. Explain Casting in Apex?

 Apex enables casting: A data type of one class can be assigned to a data type of another class, but only if one class is a child of other class.
• Casting converts an object from one data type to another.
• Casting between the generic sObject type and the specific
sObject type is also allowed.
For Example:
sObject s = new Account();
Account a = (Account)s;
Contact c = (Contact)s //this generates a run time error.

308. Explain Exceptions Statements in Apex?

Similar to Java, Apex uses exception to note errors and other events that disrupt script execution with the following

Exception statement keywords:
• Throw: signals that an error has occurred and provides an exception object.
• Try: identifies the block of code where the exception can occur.
• Catch: identifies the block of code that can handle a particular exception. There may be multiple catch blocks for each try block.
• Finally: optionally identifies a block of code that is guaranteed to execute after a try block.

Exception Example:
public class OtherException extends BaseException {}
Try{
//Add code here
throw new OtherException(‘Something went wrong here…’);
} Catch (OtherException oex) {
//Caught a custom exception type here
} Catch (Exception ex){
//Caught all other exceptions here
}

309. Name different Exceptions?

All exceptions support built-in methods for returning the error message and exception type, below is the some of the Exception Methods,
AsyncException
CalloutException
DmlException
EmailException
JSONException
ListException
MathException
NoAccessException
NoDataFoundException
NullPointerException
QueryException

310. Explain about Salesforce annotations

Apex annotations modify the way a method or class is used.

Below is the list of annotations supported by salesforce

@Deprecated

            Use the deprecated annotation to identify methods, classes, exceptions, enums, interfaces, or variables that can no longer be referenced in subsequent releases of the managed package in which they reside. This is useful when you are re-factoring code in managed packages as the requirements evolve. New subscribers cannot see the deprecated elements, while the elements continue to function for existing subscribers and API integrations.

@Future

            Use the future annotation to identify methods that are executed asynchronously. When you specify future, the method executes when Salesforce has available resources.

            To test methods defined with the future annotation, call the class containing the method in a startTest, stopTest code block. All asynchronous calls made after the startTest method are collected by the system. When stopTest is executed, all asynchronous processes are run synchronously.

@IsTest

           

            Use the isTest annotation to define classes or individual methods that only contain code used for testing your application. The isTest annotation is similar to creating methods declared as testMethod.

@ReadOnly

           

            The @ReadOnly annotation allows you to perform unrestricted queries against the Force.com database. All other limits still apply. It's important to note that this annotation, while removing the limit of the number of returned rows for a request, blocks you from performing the following operations within the request: DML operations, calls to System.schedule, calls to methods annotated with @future, and sending emails.

@RemoteAction

           

            The RemoteAction annotation provides support for Apex methods used in Visualforce to be called via JavaScript. This process is often referred to as JavaScript remoting.

@TestVisible

           

            Use the TestVisible annotation to allow test methods to access private or protected members of another class outside the test class. These members include methods, member variables, and inner classes. This annotation enables a more permissive access level for running tests only.

Apex REST annotations:

@RestResource(urlMapping='/yourUrl')

            The @RestResource annotation is used at the class level and enables you to expose an Apex class as a REST resource.

@HttpDelete

            The @HttpDelete annotation is used at the method level and enables you to expose an Apex method as a REST resource. This method is called when an HTTP DELETE request is sent, and deletes the specified resource.

@HttpGet

            The @HttpGet annotation is used at the method level and enables you to expose an Apex method as a REST resource. This method is called when an HTTP GET request is sent, and returns the specified resource.

@HttpPatch

            The @HttpPatch annotation is used at the method level and enables you to expose an Apex method as a REST resource. This method is called when an HTTP PATCH request is sent, and updates the specified resource.

@HttpPost

            The @HttpPost annotation is used at the method level and enables you to expose an Apex method as a REST resource. This method is called when an HTTP POST request is sent, and creates a new resource.

@HttpPut

            The @HttpPut annotation is used at the method level and enables you to expose an Apex method as a REST resource. This method is called when an HTTP PUT request is sent, and creates or updates the specified resource.

311. Difference between trigger.newMap and trigger.oldMap?

Trigger.newMap - A map of IDs to the new versions of the sObject records. Note that this map is only available in before update, after insert, and after update triggers.

Trigger.oldMap - A map of IDs to the old versions of the sObject records. Note that this map is only available in update and delete triggers.

312. What are the available Trigger Events?

There are 6 trigger events available.

1.     Insert

2.     Update

3.     Delete

4.     Merge

5.     Upsert

6.     Undelete

313. What are the available Trigger contest variables?

Below are the list of Trigger context variables

1.     isBefore

2.     IsAfter

3.     isInsert

4.     IsUpdate

5.     isDelete

6.     isUndelete

7.     isExecuting

8.     new

9.     old

10.  newMap

11.  oldMap

12.  size

314. What is Force.com IDE?

The Force.com IDE is a powerful client application for creating, modifying, testing and deploying Force.com applications. Based on the Eclipse platform, it provides a comfortable environment for programmers familiar with integrated development environments, allowing you to code, compile, test, and deploy all from within the IDE itself.

315. Explain the Sequence of Salesforce Triggers and Order of Execution?

 The following is the order of salesforce execution when the you create or update a record,
1) Loads the original record from the database or initializes the record for an upsert statement.
2) Loads the new record field values from the request and overwrites the old values.
If the request came from a standard UI edit page, Salesforce runs system validation to check the record for:
Required values at the layout level and field-definition level
Valid field formats (ex: zip code, country code format)
Maximum field length (ex: mobile number must 10 digits)
Salesforce doesn’t perform system validation in this step when the request comes from other sources, such as an Apex application or a SOAP API call.
3) Run all before triggers.
4) Runs most system validation steps again, such as verifying that all required fields have a non-null value, and runs any user-defined validation rules. The only system validation that Salesforce doesn’t run a second time (when the request comes from a standard UI edit page) is the enforcement of layout-specific rules.
5) Saves the record to the database, but doesn’t commit yet.
6) Run all after triggers.
7) Run assignment rules.
8) Run auto-response rules.
9) Run workflow rules.
10) If there are workflow field updates, updates the record again.
11) If the record was updated with workflow field updates, fires before and after triggers one more time (and only one more time), in addition to standard validations. Custom validation rules are not run again.
12) Run escalation rules.
13) If the record contains a roll-up summary field or is part of a cross-object workflow, performs calculations and updates the roll-up summary field in the parent record. Parent record goes through save procedure.
14) If the parent record is updated, and a grand-parent record contains a roll-up summary field or is part of a cross-object workflow, performs calculations and updates the roll-up summary field in the parent record. Grand-parent record goes through save procedure.
15) Run Criteria Based Sharing evaluation.
16) Commits all DML operations to the database.
17) Run post-commit logic, such as sending email.

316. What is Visualforce in Salesforce?

Visualforce is the component-based user interface framework for the Force.com platform. The framework includes a tag-based markup language, similar to HTML. Each Visualforce tag corresponds to a coarse or fine-grained user interface component, such as a section of a page, or a field. Visualforce boasts about 100 built-in components, and a mechanism whereby developers can create their own components.
• Visualforce pages can react differently to different client browsers such as those on a mobile or touch screen device.
• Everything runs on the server, so no additional client-side callbacks are needed to render a complete view.
• Optional server-side call outs can be made to any Web service.

Visualforce is a Web-based framework that lets you quickly develop sophisticated, custom UIs for Force.com desktop and mobile apps. Using native Visualforce markup and standard Web development technologies such as HTML5, CSS, JavaScript, and jQuery, you can rapidly build rich UIs for any app.

317. Let’s say we have to update the same record in After Trigger context. Is there any way or workaround?

If we create a new instance of a sObject in the Apex Trigger in memory using the Id of the newly created record as provided in the After Trigger context, we can perform an Update DML statement and not get a read only error. This is because in Apex, the SObject is seen as a new reference (even though the records have the same SFDC ID) and therefore is eligible for DML operations. The below snippet of code illustrated this working and not working.

List<Contact> originals = new List<Contact>();

if(mirrorResultMap.values().size() > 0)

{

    for(Contact origContact : contactRecs.values())

    {

        Contact mirrorContact = mirrorResultMap.get(origContact.Id);

        //origContact.Linked_Contact__c = mirrorContact.Id; //Link the Original Record tot he Mirror Record WILL FAIL

        Contact origContactUpdate = new Contact(Id=origContact.Id, Linked_Contact__c = mirrorContact.Id); //This will WORK

        originals.add(origContactUpdate);

    }

    //update contactRecs.values(); //Update the Records -> THIS WILL FAIL AS ITS ORIGINAL RECORDS IN MEMORY

    update originals;

}

318. System.debug() statements are included against script count?

Any statement ending with semi-colon will be included against script count.

319. While trying to access javascript code from some CDN like Google, we get error something like “attempt to run uG request”. How to resolve it?

While providing URL, do not specify the protocol.

Use like this:

<script type='text/javascript' src='//ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js'></script>

320. Explain ActionFunction, ActionSupport and ActionPoller in Visualforce.

apex:ActionFunction : This component helps to invoke AJAX request (Call Controllers method) directly from Javascript method. It must be child of apex:form.

apex:ActionSupport : This component adds Ajax request to any other Visualforce component.

Example: Commandlink button has inbuilt AJAX functionality however few components like OutputPanel does not have inbuilt AJAX capabilities. So with the help of this component, we can enable AJAX.

apex:ActionPoller : This is timer component which can send AJAX request on pre-defined interval. Minimum interval is 5 sec and default is 60 sec.

321. In how many ways you can invoke Controllers / Controller Extensions method from VF?

We can invoke Aprex Controllers or Controller Extensions using below methods.

·         Javascript Remoting

·         ActionFunction

·         ActionSupport

·         ActionPoller

322. What is the use of apex:detail component ?

With the help of this Visualforce component, we can directly get complete behavior of page layout defined for logged in user’s profile. There is no need to add fields, related lists explicitly.

323. What is the difference between “apex:dataTable” and “apex:pageBlockTable” components in Visualforce?

Both components are used to render data in tabular format.

DataTable	PageBlockTable
Not required	Should be defined inside pageBlock or pageBlockSection
No styles are used	Uses standard style sheets
Not Required	It has the required attribute “value”
We need to specify column headers explicitly	Column headers will be displayed automatically

dataTable will render records in simple HTML table format whereas the 

pageBlockTable possess default look and feel of salesforce standard CSS and must be written inside “apex:pageBlock” component and a required argument value need to be passed for pageBlockTable.

324. User have all the permissions to see the Dashboard and Source Folder still when he wants to see dashboard, it’s not visible. What might be the cause?

It is possible that Salesforce User license for Dashboard running user is different than User wants to access Dashboard.

Example – Running User license is “Salesforce” and user trying to access Dashboard is “Salesforce Platform”.

325. How to implement the pagination in SOQL?

In spring 12, Salesforce has come up with ability of SOQL to get records from position “X” instead of position “1” every time to help creating pagination feature.

Pagination in SOQL using keyword Offset

Select Id, Name from Lead LIMIT 5 OFFSET 2

Above query will return 5 Lead records starting from record number 10 (5×2).

326. How to generate the random string or random password using Apex?

Integer len = 10;

Blob blobKey = crypto.generateAesKey(128);

String key = EncodingUtil.convertToHex(blobKey);

String pwd = key.substring(0,len);

327. What is dynamic binding in salesforce?

Dynamic Visualforce bindings are a way of writing generic Visualforce pages that display information about records without necessarily knowing which fields to show. In other words, fields on the page are determined at run time, rather than compile time. This allows a developer to design a single page that renders differently for various audiences, based on their permissions or preferences. Dynamic bindings are useful for Visualforce pages included in managed packages since they allow for the presentation of data specific to each subscriber with very little coding.

Example 1:
Access the Account name from Contact.

{!myContact['Account'][fieldname]}

Consider Data type in Apex

public Map<String, List<Account>> accountsMap {get; set;}

Visualforce page:

<apex:variable value="A" var="selectedKey" />

<apex:pageBlockTable value="{!accountsMap[selectedKey]}" var="acc">

   <apex:column value="{!acc.name}"/>

   <apex:column value="{!acc.BillingStreet}"/>

   <apex:column value="{!acc.BillingCity}"/>

   <apex:column value="{!acc.BillingPostalCode}"/>

</apex:pageBlockTable>

328. How to convert lead using Apex?

Lead myLead = new Lead(LastName = 'Foo', Company='Foo Bar');

insert myLead;

Database.LeadConvert lc = new database.LeadConvert();

lc.setLeadId(myLead.id);

LeadStatus convertStatus = [SELECT Id, MasterLabel FROM LeadStatus WHERE IsConverted=true LIMIT 1];

lc.setConvertedStatus(convertStatus.MasterLabel);

Database.LeadConvertResult lcr = Database.convertLead(lc);

System.assert(lcr.isSuccess());

329. Consider total 90k records present in Salesforce and you have used the count() method of soql. What will be output of it? (we need to verify this feature in recent versions of the salesforce api’s)

It will throw an error something like “Too many query rows: 50001”, as the record limit in SOQL is 50,000.
Although the count() returns only one row however it processes each record and thus hit the allowed governor limit.

330. How to get the Recordtype Id using Dynamic Apex?

Normally to get the RecordtypeId for any sObject we use SOQL and it will count against your limit. So below method will bypass the need of SOQL Query.

Map<String, Schema.SObjectType> m  = Schema.getGlobalDescribe() ;

Schema.SObjectType s = m.get('API_Name_Of_SObject') ;

Schema.DescribeSObjectResult cfrSchema = s.getDescribe() ;

Map<String,Schema.RecordTypeInfo> RecordTypeInfo = cfrSchema.getRecordTypeInfosByName();

Id rtId = RecordTypeInfo.get('Record Type Name').getRecordTypeId();

331. Write Apex code which will take the RecordID as input and on the basis of that it will print the Object name and field names of sObject.

List<Schema.SObjectType> gd = Schema.getGlobalDescribe().Values();

Map<String,String> objectMap = new Map<String,String>();

for(Schema.SObjectType f : gd)

{

     objectMap.put(f.getDescribe().getKeyPrefix(), f.getDescribe().getName());

}

String sampleId ='00390000003LIVw';

String prefix =  sampleId.substring(0,3);

String objectName = objectMap.get(prefix);

System.debug('** SObject Name ** '+objectName);

System.debug('** SObject Name ** '+objectName);

Map<String, Schema.SObjectField> desResult = Schema.getGlobalDescribe().get(objectName).getDescribe().Fields.getMap();

List<String> fieldList = new List<String>();

fieldList.addAll(desResult.keySet());

for(integer i =0;i<fieldList.size();i++)

{

    System.debug('** Field Name ** '+fieldList[i]);

}

332.  How to get “https” link instead of “http” for Visualforce page using URLFOR() in Email Template

When you create the Link using URLFOR() in Email Template, it creates link in “http” format instead of “https” and thus causes end user to logged into salesforce again.

So instead of

<a href='{!URLFOR('/apex/SomePage', null, [id=Some_Object__c.Id,retURL="/apex/SomeOtherPage"])}'>Go to SomePage here!</a>

We can use something like :

<a href='{!SUBSTITUTE(URLFOR('/apex/SomePage', null, [id=Some_Object__c.Id,retURL="/apex/SomeOtherPage"]),'http:','https:')}'>Go to SomePage here!</a>

333. When you get the error “Non-selective query against large object type”? How to resolve it?

Whenever an object has greater than 100K records any query on that object must be “selective”. For a query to be selective it must have enough indexed filters (where clauses) so that less than 10% of the records (in our example 10K) are returned before applying the limit statement.

334. In Controller extension, you are getting the error “SObject row was retrieved via SOQL without querying the requested field” while accessing the field of parent Custom Object or standard Object for which the Controller extension was written. How to resolve that?

In Constructor of the Controller extension, only Id of Custom Object is supplied. We need to query the required field explicitly in order to use in remaining part of the code.

335. Using Apex how you can determine that user is in Sandbox or production?

By using below code, we can identify the given organization is a sandbox or production.

If the code returns true then it is a sandbox else it is a production.

public Static Boolean isSandbox(){

        String host = URL.getSalesforceBaseUrl().getHost();

        String server = host.substring(0,host.indexOf('.'));

        // It's easiest to check for 'my domain' sandboxes first

        // even though that will be rare

if(server.contains('--'))

return true;

        // tapp0 is a unique "non-cs" server so we check it now

if(server == 'tapp0')

return true;

        // If server is 'cs' followed by a number it's a sandbox

if(server.length()>2){

if(server.substring(0,2)=='cs'){

try{

Integer.valueOf(server.substring(2,server.length()));

                }

catch(exception e){

                    //started with cs, but not followed by a number

return false;

                }

                //cs followed by a number, that's a hit

return true;

            }

        }

        // If we made it here it's a production box

return false;

    }

336. Consider we have overall 90% code coverage however there is one class which has 0% code coverage. Can we still able to deploy that class on production?

Yes. Minimum 1% required for every trigger and there is no such restriction for Apex class.

338. In Ajax toolkit for custom Javascript button, you have to explicitly login to API because global Session variable is not available. In that case it is security vulnerable because anybody logged in can see the javascript code and your username and password. So is there any way to avoid this?

We can create a visualforce page with output type as JavaScript. Global session variable is available in VF page.

Initialize the global javascript variable in that VF page. include VF page as a javascript file and we are done!

339. In Custom Component How we can return value to Custom Controller or Controller Extension?

In Apex, Objects are passed by reference.  So supply an argument of wrapper class (object) type to custom component. If its value is changed in Custom component we will get updated value in controller also.

340. Let’s consider you had created outbound changeset previously. After that, some class is modified which is part of that old changeset. If you clone that Changeset, current updated class will be included or that previous class will be included in changset? (This need to be verified in recent versions)

Once changeset is created it cannot be modified. After creation of changset, if we modify any component it will not reflected and when we clone the changeset, all components (of course old copy of component) will be added to changeset.

341. In trigger, let’s say we have system.debug() statement after adderror() method. Will system.debug() be statement executed in Trigger after adderror() method?

adderror() method is not error statement rather its normal execution flow and all the statements written after adderror() will be executed normally.

342. What will happen if you try to update record in After Trigger Context?

You will get an error saying “record is Read only”.

343. Can you use aggregate expressions inside inner query?
Explanation – Can you use Group by clause inside inner query in SOQL?

Example: Something like :

SELECT Id, Name,(SELECT Count(Id),Name FROM Contacts Group By Name Havingcount(Id) > 1 ) FROM Account

No. only root queries support aggregate expressions. Return type is List<AggregateResult> for above query However the root result expects List<Account> and there is no syntax or provision available in Salesforce to specify that child results are of type “AggregateResult“.

344. What is the best way to check whether organization has PersonAccount enable or not using Apex?

Method 1:

// Test to see if person accounts are enabled.

public Boolean personAccountsEnabled()

{

    try

    {

            // Try to use the isPersonAccount field.

        sObject testObject = new Account();

        testObject.get( 'isPersonAccount' );

        // If we got here without an exception, return true.

        return true;

    }

    catch( Exception ex )

    {

        // An exception was generated trying to access the isPersonAccount field

        // so person accounts aren't enabled; return false.

        return false;

    }

}

Method 2:

// Check to see if person accounts are enabled.

public Boolean personAccountsEnabled()

{

    // Describe the Account object to get a map of all fields

    // then check to see if the map contains the field 'isPersonAccount'

    return Schema.sObjectType.Account.fields.getMap().containsKey('isPersonAccount' );

}

345. How to get selected records ID from List View using Javascript / Ajax Toolkit, when custom button is added on List View page?

Create a new Button on Lead of type List Button. Add the button on Lead List View Layout and write below Javascript code:

{!RequireScript("/js/functions.js")}

var recordsSelected = {!GetRecordIds($ObjectType.Lead)}

for(var i=0; i < recordsSelected .length ; i++) {

     alert('Selected ID '+recordsSelected[i]);

}

346. What is the default timeout period while calling webservice from Apex.

10 sec.

347. A single Apex transaction can make how many callouts to an HTTP request or an API call?

Maximum 10 callouts

348. How to increase timeout while calling web service from Apex?

docSample.DocSamplePort stub = new docSample.DocSamplePort();

stub.timeout_x = 2000; // timeout in milliseconds

349. How to show loading image while Ajax call in Visualforce? OR how to show image in <apex:actionStatus> tag in Visualforce?

<div style="position:absolute;top:20px;left: 50%;">

            <apex:actionStatus id="refreshContent" >

                        <apex:facet name="start" >

                                    <apex:image url="{!$Resource.LoadingImage}" />

                        </apex:facet>

            </apex:actionStatus>

</div>

350. How to add the Document Header in Visualforce page?

Directly there is no way to add the document type in visualforce. However in most of the cases IE9 does not work with Visualforce pleasantly. And then we need to add the Document type in header. So following workaround will work.

<apex:outputText escape="false" value="{!'<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Strict//EN\" \"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd\">'}"/>

<html>

    <head>

        <title>test</title>

    </head>

    <body>test</body>

</html>

</apex:page>