Accessing One table with multiple Threads and Inserting Values

[Guneet Aulakh]

Hello fellow members!

I am trying to save values to a table in Access, I have 3 threads that update this single table, but it seems to be overwriting the values in the table. Could any of you please guide me on what I am dooing wrong. The code is as follows:

Here are the 3 threads:

 
        workingThread1.StartThreads(thWorker1);
        workingThread2.StartThreads(thWorker2);
        workingThread3.StartThreads(thWorker3);
 

Here is the part from the run() where I call the JDBC:

 
        odataBase.CdataBaseInsert(x, y);
        odataBase.CdataBaseRead(); 

Here is the part where we Update and Read the DB:

  
public class CdataBase {
    int x;
    int y;
    
    public void CdataBaseInsert(int x, int y){
        this.x = x;
        this.y = y;       
        
        
        try {
            synchronized(this){
            Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
            // set this to a MS Access DB you have on your machine
            String filename = "c:/Thesis/Simulation    Data/CsimulationData.mdb";
 
            String database = "jdbc:odbc:Driver={Microsoft Access Driver (*.mdb)};DBQ="; 
 
            database+= filename.trim() + ";DriverID=22;READONLY=false}"; // 
            Connection con = DriverManager.getConnection( database ,"","");
            
            PreparedStatement s = con.prepareStatement("Update Handoff_Log SET Init_Cell = ?, Final_Cell =?");
                        
            s.setInt(1, x);
            
            s.setInt(2, y);
            
            s.executeUpdate();
                       
            s.close();
            con.close();
     
            }//end synchronize
           
            
        }
 
            catch (Exception e) {
            System.out.println("Error: " + e);
        }
        
    }
    
    public void CdataBaseRead(){
        try {
            synchronized(this){
                Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
                // set this to a MS Access DB you have on your machine
                String filename = "c:/Thesis/Simulation Data/CsimulationData.mdb";
 
                String database = "jdbc  :o  dbc  :D  river={Microsoft Access Driver (*.mdb)};DBQ="; 
 
                database+= filename.trim() + ";DriverID=22;READONLY=false}"; // 
 
                Connection con = DriverManager.getConnection( database ,"","");
 
    
        Statement s = con.createStatement();
        
        ResultSet rs = s.executeQuery("Select Init_Cell, Final_Cell from Handoff_Log");
        
if (rs != null) while ( rs.next() ){
        System.out.println("Data from Init_Cell: " + rs.getString(1) );
    System.out.println("Data from Final_Cell: " + rs.getString(2));
                }//end while

s.close();
con.close();
    }
     }//end try
            catch (Exception e) {
                System.out.println("Error: " + e);
            }//end catch
 
    }//end CdataBaseRead
}//end of class
 
 

Here is the output

Thread : Thread-0
Data from Init_Cell: 0
Data from Final_Cell: 18

Thread : Thread-1
Data from Init_Cell: 4
Data from Final_Cell: 13

Thread : Thread-2
Data from Init_Cell: 7
Data from Final_Cell: 14

When I check the Table in the DB all is see is the last entry of 7 and 14, while the rest are missing!

Your suggestions and support are much appreciated.

Guneet

[edited to disable smilies]
[ December 27, 2004: Message edited by: Jeanne Boyarsky ]

[Jeanne Boyarsky]

Guneet,
Welcome to JavaRanch!

What do you expect to see? Each time the update statement runs, it overwrites the previous values in the table. So after the threads are finished, you would see the results of whatever thread happened to run last.

[Guneet Aulakh]

Please forgive my ignorance, but should I be trying Insert here, rather then update. It is 12 in the night! I will try with the insert, first thing in the morning, and post a reply here.

Thanks

Guneet

[Jeanne Boyarsky]

Guneet,
Yes! It should work with insert.