Sending Mass Email Through Apex Controllers

This tip demonstrates how to send mass emails along with attachments(pdf/resources/assets etc) through Apex Controllers.
Apex Controllers

/**
*@purpose : Method for Creating an Attachment
*@param : None
*@return : PageReference to convertpdf Page
**/
public PageReference attachpdf() {

   //Parameters getting from the URL
    Id quoteId = ApexPages.currentPage().getParameters().get('quoteId');
    Id cId = ApexPages.currentPage().getParameters().get('cId');
    Quote quoteObj = [select id,name from Quote where id =:quoteId];

   //Referring from the Pdf page(The page which is rendered as PDF)
    PageReference pdfPage = Page.pdfPage;
    pdfPage.getParameters().put('id',quoteid);
    Blob pdfBlob = pdfPage.getContent();
 
   //Creating a Attachment
    Attachment attachmentObj = new Attachment(parentId = quoteObj.id, name=quoteObj.name + '.pdf', body = pdfBlob);
    INSERT attachmentObj;
    PageReference nextPage = new PageReference('/apex/convertpdf?cId='+cId+'qId='+quoteId);
    ApexPages.addMessage(new ApexPages.message(ApexPages.severity.INFO,'PDF Attached Successfully'));
    return nextPage;
}


/**
*@purpose : Method for Sending Mass mail along with the Attachment
*@param : None
*@return : PageReference to convertpdf Page
**/
public PageReference sendEmail(){  

   //Parameters getting from the URL
   Id quoteId = ApexPages.currentPage().getParameters().get('quoteId');
   Id emailTemplate = ApexPages.currentPage().getParameters().get('emailTemplate');
   Id cId = ApexPages.currentPage().getParameters().get('cId');
   Id aId = ApexPages.currentPage().getParameters().get('aId');
  List<Contact> contactNames = [SELECT id, name FROM Contact WHERE AccountId =: aId];
   for (String obj : contactNames){
      contact = [SELECT Id,name,email FROM Contact WHERE name =:obj];
      for(Integer i=0; i < contact.size(); i++){

       //Initializing for Sending Mails(Written Single because of in a loop)
         Messaging.SingleEmailMessage email = new Messaging.SingleEmailMessage();

       //Initializing the Email Attachment
         List<Messaging.Emailfileattachment> fileAttachments = new List<Messaging.Emailfileattachment>();

       //Attaching them to the mail by setting the parameters
         for (Attachment attachmentObj : [SELECT Name, Body, BodyLength FROM Attachment WHERE ParentId = :quoteId]){
            Messaging.Emailfileattachment efa = new Messaging.Emailfileattachment();
            efa.setFileName(attachmentObj.Name);
            efa.setBody(attachmentObj.Body);
            fileAttachments.add(efa);
         }

       //Setting the Template and Target Ids
         email.setFileAttachments(fileAttachments);
         email.setTargetObjectId(contact[i].Id);
         email.setTemplateId(emailTemplate.id);

       //Sending the Mail
         Messaging.sendEmail(new Messaging.SingleEmailMessage[] { email });
      }
   }
   PageReference nextPage = new PageReference('/apex/convertpdf?quoteId='+quoteId+'&cId='+cId);
   ApexPages.addMessage(new ApexPages.message(ApexPages.severity.INFO,'Email Sent Successfully'));
   return nextPage;
}

IMPORTANT POINTS
1) setFileAttachments = Attaching the files to the Mail
2) setTargetObjectId = Setting the Target Ids(Contacts to whom the mail is to be send)
3) setTemplateId = Format of the Mail by setting the Template Format
4) Messaging.sendEmail = Sending the Mail

#Note: It is good to use "Messaging.SingleEmailMessage"  within a loop rather than "Messaging.MassEmailMessages".