Trigger and it's handler class example with design pattern.

Please check my previous post (Trigger and it's handler class structure for your organisation.), where I mentioned the architectural structure to design or handle trigger for your organisation.

For the same you should have the below apex classes and trigger,

1. TriggerHandlerException class [Handled exception].
2. TriggerHandler class [An abstract class where all trigger related operations have been structured as a template].
3. TriggerFactory class [Factory of Concrete Trigger Handler classes].
4. TriggerWorker class [This is the worker class for trigger. Each and every trigger just call "executeTrigger()" method of this worker class].
5. ConcreteTriggerHandler class [This is the main handler class, where the actual logic will be define and this class extend TriggerHandler abstract class and defined all abstract method].
6. Trigger for an SObject [From here only call the "executeTrigger()" method of this TriggerWorker class with string parameter as "ConcreteTriggerHandler class name"].


Suppose we want to create a trigger of Account object, then the source code will be as follows,

1. TriggerHandlerException

/*
 * Author : Arun Kumar Hazra
 * Date : 16-NOV-2017
 *
 * Description : This is custom exception calss and fire while trying to create an
 * handler instance which is not registered.
 *.
 */
public class TriggerHandlerException extends Exception {}

2. TriggerHandler

/*
 * Author : Arun Kumar Hazra
 * Date : 16-NOV-2016
 *
 * Description : This abstract class is responsible to create a template to handle trigger operations.
 *               All Trigger Handlers must implement to enforce best practice.
 */
public abstract class TriggerHandler{
    //Template method
    public void doExecute(){
        // Before Trigger
        if (Trigger.isBefore){
            // Iterate through the records to be deleted passing them to the handler.
            if (Trigger.isDelete)
            {
                beforeDelete(Trigger.old, Trigger.oldMap);
            }
            // Iterate through the records to be inserted passing them to the handler.
            else if (Trigger.isInsert)
            {
                beforeInsert(Trigger.new);
            }
            // Iterate through the records to be updated passing them to the handler.
            else if (Trigger.isUpdate)
            {
                List<SObject> lstOfNewSo = new List<SObject>();
                for (SObject so : Trigger.old)
                {
                    lstOfNewSo.add(Trigger.newMap.get(so.Id));                        
                }
                beforeUpdate(Trigger.old, lstOfNewSo, Trigger.oldMap, Trigger.newMap);
            }

        } else { // After Trigger
            // Iterate through the records deleted passing them to the handler.
            if (Trigger.isDelete)
            {
                afterDelete(Trigger.old, Trigger.oldMap);
            }
            // Iterate through the records inserted passing them to the handler.
            else if (Trigger.isInsert)
            {
                afterInsert(Trigger.new, Trigger.newMap);
            }
            // Iterate through the records updated passing them to the handler.
            else if (Trigger.isUpdate)
            {
                List<SObject> lstOfNewSo = new List<SObject>();
                for (SObject so : Trigger.old)
                {
                    lstOfNewSo.add(Trigger.newMap.get(so.Id));
                }
                afterUpdate(Trigger.old, lstOfNewSo, Trigger.oldMap, Trigger.newMap);
            }
    
        }
    }
    //############################### After operations ###############################
    /*
     * This method is called iteratively for each record inserted during an AFTER trigger.
     */
    
    //@TestVisible
    abstract void afterInsert(List<SObject> lstOfNewSo, map<id,SObject> mapOfNewSo);
    /*
     * This method is called iteratively for each record updated during an AFTER trigger.
     */
    
    
    abstract void afterUpdate(List<SObject> lstOfOldSo, List<SObject> lstOfNewSo, map<id,SObject> mapOfOldSo, map<id,SObject> mapOfNewSo);
    /*
     * This method is called iteratively for each record deleted during an AFTER trigger.
     */
    
    
    abstract void afterDelete(List<SObject> lstOfOldSo, map<id,SObject> mapOfOldSo);
    //############################### Before operations ###############################
    /*
     * This method is called iteratively for each record inserted during an BEFORE trigger.
     */
    
    
    abstract void beforeInsert(List<SObject> lstOfNewSo);
    /*
     * This method is called iteratively for each record updated during an BEFORE trigger.
     */
    
    
    abstract void beforeUpdate(List<SObject> lstOfOldSo, List<SObject> lstOfNewSo, map<id,SObject> mapOfOldSo, map<id,SObject> mapOfNewSo);
    /*
     * This method is called iteratively for each record deleted during an BEFORE trigger.
     */
    
    
    abstract void beforeDelete(List<SObject> lstOfOldSo, map<id,SObject> mapOfOldSo);
}

3. TriggerFactory

/*
 * Author : Arun Kumar Hazra
 * Date : 16-NOV-2016
 *
 * Description : This is a factoy class of all triggers, existes in this ORG. This factory is responsible for
 *               creating factory of trigger handler class.
 */
public with sharing class TriggerFactory{
    /*
     * This method return instance of TriggerHandler.
     * Arguments:   String className - Name of handler class in string format.
     * Return triggerHandler : Instance of trigger handler class.
     *  
     */
    public static TriggerHandler getHandlerInstance(String className){
        TriggerHandler handler = getHandler(className);
        // Make sure we have a handler registered, new handlers must be registered in the getHandler method.
        if (handler == null){
            throw new TriggerHandlerException('No Trigger Handler registered of name : ' + className);
        }        
        return handler;
    }
    
    /*
     * private static method to get the appropriate handler for the object type.
     * Modify this method to add any additional handlers.
     * Arguments:   String className - Name of handler class in string format.
     * Returns:     A trigger handler if one exists or null.
     */
    private static TriggerHandler getHandler(String className){
        if (className != null && className.trim().length() > 0){
            Type t = Type.forName(className);
            return (TriggerHandler) t.newInstance();
        }        
        return null;
    }
}

4. TriggerWorker

/*
 * Author : Arun Kumar Hazra
 * Date : 16-NOV-2016
 *
 * Description : This is the first entry point for each trigger.
 *.
 */
global with sharing class TriggerWorker{
    /*
     * This static method is responsible to execute trigger logic with help of handler class.
     * Arguments:   String className - Name of handler class in string format.
     *  
     */
    global static void executeTrigger(String className){
        TriggerHandler handler = TriggerFactory.getHandlerInstance(className);
        handler.doExecute();
    }
}

5. AccountTriggerHandler  (ConcreteTriggerHandler class)

/**
* Trigger Handler class for Expense Detail Objcet.
*
**/
public class AccountTriggerHandler extends TriggerHandler{
    // ########### Start of defining abstract methods of Trigger Handler abstract class ###########
    public void afterInsert(List<SObject> lstOfNewSo, map<id,SObject> mapOfNewSo){
        sampleMethod(lstOfNewSo);

    }
    
    public void afterUpdate(List<SObject> lstOfOldSo, List<SObject> lstOfNewSo, map<id,SObject> mapOfOldSo, map<id,SObject> mapOfNewSo){
        
    }
    
    public void afterDelete(List<SObject> lstOfOldSo, map<id,SObject> mapOfOldSo){
        
    }
    
    public void beforeInsert(List<SObject> lstOfNewSo){
        
    }
    
    public void beforeUpdate(List<SObject> lstOfOldSo, List<SObject> lstOfNewSo, map<id,SObject> mapOfOldSo, map<id,SObject> mapOfNewSo){
        
    }
    
    public void beforeDelete(List<SObject> lstOfOldSo, map<id,SObject> mapOfOldSo){
        
    }
    // ########### End of defining abstract methods of Trigger Handler abstract class ###########
    

    /* here create private method(s) to perform your operation and call that method(s) 

     * from above template method based on the scenario. Suppose we need perform an 

     * operation after a record insertion, so create a private method say sampleMethod() and 

     * call it from above afterInsert() method. */

   private void sampleMethod(lstOfNewSo){

        //Perform your logic.

   }

       
}

6. AccountTrigger

trigger AccountTrigger on Account(after insert, after update, after delete, before insert, before update, before delete) {
   // Method parameter as concrete trigger handler class name.

   TriggerWorker.executeTrigger('AccountTriggerHandler');
}

Trigger and it's handler class structure for your organisation.

This is a sample structure to make your organization's triggers and their's handler class in a maintainable way. Check the coding example in next post.

Scheduler class example for batch apex.

Assume that our ORG has a custom object API named as "Product_Complaint__c".
Our aim is to schedule a batch apex which will responsible for make a select query on Product_Complaint__c object.

/**
 * This is a batch class.
 * https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_batch_interface.htm
 **/
global class BatchClassExample implements Database.Batchable<sObject>{
  global String query;

  global Database.QueryLocator start(Database.BatchableContext BC){
      return Database.getQueryLocator(query);
    }

    global void execute(Database.BatchableContext BC, List<sObject> scope){
       List<Product_Complaint__c> lstOfPC = (List<Product_Complaint__c>)scope;

       // Call any helper calss to do the logic.
       System.debug('Test PC Size ::::::::::::: ');
       System.debug('PC Size ::::::::::::: '+ lstOfPC.size());
   }


    global void finish(Database.BatchableContext BC){
    }
}

/**
 * This is a scheduler class example for batch apex.
 * This class implements the Schedulable interface for a class called AffectedScheculeClassExample.
 * 
 * Link: https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_scheduler.htm
 **/
global class ScheduledBatchClassExample implements Schedulable {
  //This is implemented method and it must be declared as global or public.
  global void execute(SchedulableContext sc) {
    BatchClassExample batchInst = new BatchClassExample();
    batchInst.query = 'SELECT Id FROM Product_Complaint__c';
    database.executebatch(batchInst, 1);
  }
}

/**
 * This class is responsible for calling ScheduledBatchClassExample class to run the scheduler.
 * Call this class constractor from anonymous window.
 *
 **/
public class CallScheduledBatchClassExample
{
  //Constructor need to be call from annonymous window to run the schedule job.
  public CallScheduledBatchClassExample(){
    ScheduledBatchClassExample schBatchClsExmpl = new ScheduledBatchClassExample();
    /**
      *  Schedule structure:
      *  <Seconds> <Minutes> <Hours> <Day_of_month> <Month> <Day_of_week> <Optional_year>
      *
      * For below example it will schedulw the job @ 08:23 AM every day.
    */
    String sch = '0 23 8 * * ?';
    String schJobID = system.schedule('Scheduler Batch Example', sch, schBatchClsExmpl);
  }
}

To test this example instantiate CallScheduledBatchClassExample() 
from anonymous window as,
CallScheduledBatchClassExample inst = new CallScheduledBatchClassExample
();

Apex Scheduler Example.

Check the class descriptions .....

/**
 * This is a simple class called from scheduler class.
 *
 **/
public class AffectedScheculeClassExample {
  public AffectedScheculeClassExample() {
    System.debug('Calling from scheduler class for testing ...... ');
  }
}

/**
 * This is a scheduler class example.
 * This class implements the Schedulable interface for a class called AffectedScheculeClassExample.
 * 
 * Link: https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_scheduler.htm
 **/
global class ScheduledClassExample implements Schedulable {
  //This is implemented method and it must be declared as global or public.
  global void execute(SchedulableContext sc) {
    AffectedScheculeClassExample affectedSchClassExmpl = new AffectedScheculeClassExample();
  }
}

/**
 * This class is responsible for calling scheduler class named as ScheduledClassExample to run at schedule time.
 * Call this class constractor from anonymous window.
 **/
public class CallScheduledClassExample {
  //Constructor need to be call from annonymous window to run the schedule job.
  public CallScheduledClassExample(){
    ScheduledClassExample schClsExmpl = new ScheduledClassExample();
    /**
      *  Schedule structure:
      *  <Seconds> <Minutes> <Hours> <Day_of_month> <Month> <Day_of_week> <Optional_year>
      *
      * For below example it will schedulw the job @ 02:28 AM every day.
    */
    String sch = '0 28 2 * * ?';
    String schJobID = system.schedule('Scheduler Example', sch, schClsExmpl);
  }
}

To test this example instantiate CallScheduledClassExample() 
from anonymous window as,
CallScheduledClassExample inst = new CallScheduledClassExample();

apex:actionSupport with apex:param example.

1. Create apex class as below example.

/**
 * Controller class for actionSupport with passing parameter example.
 *
 **/
public with sharing class ActionSupportExamCtrl
{
 //Variable responsible for holding param value assigned in from VF.
 public String param1{get;set;}

 //action method called from actionFunction.
 public void method1(){
  System.debug('Parameter passed is '+ param1);
 }
}

2.Create VF as below example.

<apex:page  controller="ActionSupportExamCtrl">
<apex:form id="formId">
<!-- apex:actionSupport with apex:param -->
<apex:inputCheckbox>
   <apex:actionSupport action="{!method1}" event="onclick" rerender="formId">
<apex:param assignTo="{!param1}" name="prmNm" value="[ Your param value ]"/>
</apex:actionsupport>
</apex:inputCheckbox>
Click on checkbox to pass parameter from action support.
    </apex:form>
</apex:page>

apex:actionFunction with apex:param example.

1. Create an apex class as below example.

/**
 * Controller class for actionFunction with passing parameter example.
 *
 **/
public with sharing class ActionFunctionExmpCtrl
{
 //Variable for input text used in VF.
 public String firstName{get;set;}
 //Variable responsible for holding param value assigned in from VF.
 public String param1{get;set;}

 //action method called from actionFunction.
 public void method1(){
  System.debug('Parameter passed is '+ param1);
 }
}

2. Create a page like below example.

<apex:page controller="ActionFunctionExmpCtrl">
<script>
/**
 * JS method call from onClick operation.
 */
function doJSMethod(fst_name) {
//Varibale to fetch the valuse passed as a parameter on onClick event.
var fstNm = document.getElementById(fst_name).value;
//actionFunction name with parameter.
callMethod1(fstNm);
}
</script>

<apex:form id="formId">
First Name: <apex:inputText id = "f_Nm" value="{!firstName}"/><br/>
<apex:inputCheckbox onclick="doJSMethod('{!$Component.f_Nm}')"/>Click on checkbox to pass First Nmae as parameter

<!-- apex:actionFunction with apex:param -->
<apex:actionFunction action="{!method1}" name="callMethod1" rerender="formId" >
       <apex:param assignTo="{!param1}" name="prmNm" value=""/>
   </apex:actionFunction>

    </apex:form>

</apex:page>

Sample example for consuming Rest Web Service (RestWSSampleWithParam) containing web method with parameters from same Salesforce ORG.

Scenario: Suppose we have a rest web service in ORG1 (As posted in previous post named as "RestWSSampleWithParam"). This service has a web method (getRestSampleResponse) which contains 2 parameters. Now our aim is to call the web service from same ORG (ORF1).

Solution: Below is the apex code example for consuming rest web service from same Org.
Pre-step: Before copy paste the below code base, do the remote site setting for the endPoint URL.

/**
 * Consuming Rest Web Service (RestWSSampleWithParam) from same ORG with parameters.
 **/
public class RestWSWithParamsConsumeFromSameOrg
{
  public static void callingRestWS(){
    try {
      // Setup remote site setting for the below URL.
          String url = 'https://ap5.salesforce.com/services/apexrest/RestWSSampleParamExmpl';
          system.debug('Response URL'  +url);   
          
          HttpRequest req = new HttpRequest();
          req.setMethod('POST');
          //req.setHeader('content-type', 'application/json');
          req.setHeader('Content-Type', 'application/xml; charset=utf-8');
          req.setEndpoint(url);   
          req.setHeader('Authorization', 'OAuth '+UserInfo.getSessionId());
          req.setBody('<?xml version="1.0" encoding="UTF-8" ?><request><firstName>Arun</firstName><lastName>Hazra</lastName></request>');
    
          Http http = new Http();
          
          HTTPResponse resp = http.send(req);
          
          system.debug('Response body'  +resp.getBody()); 
          system.debug('STATUS: '+ resp.getStatus());
          system.debug('STATUS_CODE:'+ resp.getStatusCode());    
    } catch(System.CalloutException e){
      System.debug('Sorry, You have an error ' + e.getMessage());
    }
  }
}