Salesforce Apex Code for Email Template | How to send

1. trigger LeadBeforeUpdate on Lead (before update)
2. {      
3.  
4. //Prefetch email Template id
5. EmailTemplate et = [SELECT id FROM EmailTemplate WHERE Name = 'Lead_Rejected'];
6.  
7. //Grab the recipient as Contact
8. Contact recipient = [SELECT id, firstname FROM Contact where id in :Trigger.newMap.keySet()];    
9.  
10. //Map the profile
11. Map<Id, Profile> ProfileOwner = new Map<Id, Profile>([Select p.Id, p.Name from Profile p where Id =: userinfo.getProfileId()]);
12.  
13. //Lead Object Map
14. Map<Id, Lead> LeadMap = new Map<Id,Lead>([Select Id, From Lead WHERE id in :Trigger.newMap.keySet()]);
15.  
16. for (lead myLead : Trigger.new)
17.     {  
18.        
19.         Lead testLead = LeadMap.get(myLead.id);
20.  
21.         if(testLead.Status__c=='Approved') {
22.            
23.     /*---Mail to the Lead Owner **********/
24.    Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage(); // new mail object
25.  
26.    //Depending on Schema your organization have
27.    recipient.AccountId = opp.AccountId;  // receipient would be owner of Lead  
28.     mail.setSenderDisplayName(ProfileOwner.get(userInfo.getUserId).Name);//Sender would be owner of Profile
29.  
30. //Notice : How I retrieve profile by passing value of current user id (using UserInfo Method)
31.   mail.setTargetObjectId(recipient.id); //target to receipient
32.   mail.setTemplateId(et.id);           // pull the email template through id
33.   Messaging.sendEmail(new Messaging.Singleemailmessage[] {mail});  //send single email
34.  
35. } // end if
36. } // end for