Sending Email in background

[Anurag Dhiman]

Hello Everyone!
I have written a code for sending emails based on time. These emails will delivered 24 hrs and 2 hrs before the specified time. But the problem is when I am running the code code eclipse the emails are going properly but when I am exporting a WAR file and deployed it on tomcat the email is going repeatedly for four times.
For this I have used java Timer class which is keep running in background and if the time difference matched the email status will update in DB after emails sent once. I need your help guys. Please suggests some idea how to prevent email for sending repeatedly. Is this a code problem or Tomcat?

Here is my code snippets

package javafiles;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.text.DecimalFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;

import org.apache.log4j.Logger;

import com.teknika.model.JavaToMysqlDate;
import com.teknika.servlet.ActionController;
import com.teknika.util.DBUtil;

public class FunctionRemderEmail {
	
Connection c=null;
	
	int count = 0;
	
	public void runFunctionCheck() {
		Timer timer = new Timer();
		TimerTask tt = new TimerTask(){
			@SuppressWarnings("unused")
			final int MILLI_TO_HOUR = 1000 * 60 * 60;
			public void run(){
			 
						System.out.println("doing the scheduled task for function reminder"); 
		
					try {
						
						
						//Getting Current date and time
					    String currentTime = new SimpleDateFormat("hh:mm a").format(new Date());
					    SimpleDateFormat sdfDate = new SimpleDateFormat("MM/dd/yyyy"); 
					    Date now = new Date();
					    String todaysDate = sdfDate.format(now);
					    System.out.println("Today date : " +todaysDate);
						
						//Connecting to the DB
						Connection c=DBUtil.getConnection();
						ResultSet rs=null;
						String qry = "select * from teknika_function_db";
						Statement s= c.createStatement();
							rs = s.executeQuery(qry);
							
							
							    while(rs.next()){
								
						
							    String mailStatus=rs.getString(11);
							    System.out.println("Mail status:  "+mailStatus);
							    
							    if(mailStatus.equals("0")){
							    	
							    String functionDate=rs.getString(2); 
							    String functionTime=rs.getString(3); 
							  
							    System.out.println("Function date and time:  "+functionDate +"  "+functionTime);
							   
								   
						
									JavaToMysqlDate j = new JavaToMysqlDate();
									String funDate= j.SqlToJsp(functionDate);
									System.out.println("function date : " +funDate);
								
									String format = "MM/dd/yyyy hh:mm a";
									 
						            SimpleDateFormat sdf = new SimpleDateFormat(format);
						 
									
									    Date dateObj1 = sdf.parse(todaysDate + " " + currentTime);
							            Date dateObj2 = sdf.parse(funDate + " " + functionTime);
							            
							            System.out.println("function parse : "+funDate + " " + functionTime);
							            
							            System.out.println(dateObj1);
							            System.out.println(dateObj2 + "\n");
									
							            DecimalFormat crunchifyFormatter = new DecimalFormat("###,###");
							            
							            long diff = dateObj2.getTime() - dateObj1.getTime();
							 
							            int diffhours = (int) (diff / (60 * 60 * 1000));
							            System.out.println("difference between Hours: " + diffhours);
							 
							            int diffminutes = (int) (diff / (60 * 1000));
							            System.out.println("difference between Minutes: " + crunchifyFormatter.format(diffminutes));
							 
															 
							            long diffSeconds = diff / 1000;
							            
							            System.out.println("Difference in seconds : " +diffSeconds);
								    
								    if(diffminutes == 1440 ||  diffminutes == 120 ){
								    	
								    	
								    	System.out.println("Difference occur to send function reminder email");
								   
								    	String inviteBy = rs.getString("invited_by");
								    	String whatFunction = rs.getString("function_type");
								    	String venueFunction = rs.getString("function_venue");
								    	
								    	String function_mail_body="<p><b>Respected Sir,</b></p>"+"<p>This is to inform you that you have been invited by"+" "+inviteBy+" "+"for"+" "+whatFunction+"</p>"+"<p>Date : "+funDate+"</p>"+"<p>Time: "+functionTime+"</P>"+"<p>Venue details : "+venueFunction +"</p>"+"<p><b>Regards,</b></p>"+"<p><b>RC-PIT</b></p>";
										
								    	SndMailToMultipleUsers.email_fun(function_mail_body);
											
								    	
										
										Statement stmt= c.createStatement();
										String query = "update teknika_function_db set mail_status=1";
										stmt.executeUpdate(query);
									
										 String status=rs.getString(11);
										    System.out.println("Changed Mail status:  "+status);
								    	
								    
								    }
								 
								 else {
									 System.out.println("No difference");
								 }
								
							    }
								    else {
								    	
								    	//Do nothing
								    }
							
								    
							}
					
					}catch (Exception e){
						
						System.out.println("Mail not sent");
						System.out.println("Exception : " +e);
						
						
					}	finally {
						if (c != null) {
						try {
							
							c.close();
						} catch (SQLException e) {
							// TODO Auto-generated catch block
							System.out.println("Error in connection close" +e);
							e.printStackTrace();
						}
					}
					
			}	
					
			}
		};
		 
		timer.schedule(tt, 60000,10000*6);
		
		
	}

}

[Anurag Dhiman]

Sorry!
From next time I'll be very careful!

[Ulf Dittmer]

We don't know the data that is retrieved from the DB, but since the whole thing is in a loop, I suppose it's possible that the mail sending is triggered many times, depending on the data.

Since the Timer goes out of scope I'd assume that it's possible that it will stop working at some random moment because it is GC-ed (I guess that they're not eligible for GC because the JVM holds references to them even if the application code does not).

[Ulf Dittmer]

What type does "mailStatus" have in the DB? Line 55 treats it as string, whereas line 115 treats it as integer.

[Anurag Dhiman]

Thanks Ulf Dittmer!
Seems a valid reason in your comment. I'll do some more research on it get back to you!

[Anurag Dhiman]

mailStatus is a varchar type in DB so I think it can handle line 115 without any problem!

[Ulf Dittmer]

mailStatus is a varchar type in DB so I think it can handle line 115 without any problem!

It looks like sloppy coding to me, though.