closing connection?

[sahar sa]

Dear friends,
I have a problem with making and closing the connection to my data base.
let me explain, I closed my CONNECTION and PSTMT after insert query but when I run this code after the first round I get the below error :
code:
trigger code:

 DB2 DB2= new DB2(); 
 for (int i=0;i<7;i++)
 {
 DB2.insert("Celeron","Intel2",85,106,0.33,3,2.5,0.33,7,0.33);
 }

insert code:

      public static void insert(final String Name,final String Manfac, final double Pmax,
      final double Pmin,final double Pw,final double Qmax,final double Qmin,final double Qw,
      final double Deadline,final double Tw) 
    {   
        Connection conn = null;
        PreparedStatement pstmt = null;

        try{
             Connection con = getConnection();
             String insert="insert into tbuyer(name,manfac,pmax,pmin,pw,qmax,qmin,qw,deadline,tw)"
             + " values(?,?,?,?,?,?,?,?,?,?)";
             pstmt = con.prepareStatement(insert);
             pstmt.setString(1,Name);
             pstmt.setString(2,Manfac);
             pstmt.setDouble(3,Pmax);
             pstmt.setDouble(4,Pmin);
             pstmt.setDouble(5,Pw);
             pstmt.setDouble(6,Qmax);
             pstmt.setDouble(7,Qmin);
             pstmt.setDouble(8,Qw);
             pstmt.setDouble(9,Deadline);
             pstmt.setDouble(10,Tw);
             int row=pstmt.executeUpdate();
             System.out.println(row+" rows was effected");
             System.out.println("Good was inserted into DB2: Name: "+Name +", "+Manfac
             +", "+"Quality:"+Qmax+", "+Qmin+", "+Qw+" Price:"+Pmax+", "+Pmin
             +", "+Pw+" Deadline:"+Deadline+", "+Tw);
             pstmt.close();
             con.close();
        }
                    
        catch(SQLException ex)
        {
        System.out.println("SQLException: " + ex.getMessage());
        System.out.println("SQLState: " + ex.getSQLState());
        System.out.println("VendorError: " + ex.getErrorCode());
        }
        catch(Exception ex){ex.printStackTrace();}

    }

error:

SQLException: No operations allowed after connection closed.
SQLState: 08003
VendorError: 0

so according to this error I should remove closing conn and pstmt but in all the examples I found they closed them.

Can some one tell me what will happen if i do not close my CONNECTION and PSTMT after insert, delete or select?

thnx,
Sahar.

[Paul Sturrock]

If you do not close them the resources remain in use and quickly you will run out of available connections to your database. When you open a connection you should always close it in a finally block.

[sahar sa]

Dear,
Do I need to close it in a finally block? Because I usually call this MySQL queries from another class, so it reurns me a result set (after I will proceed on result set some) and then I close it by calling DB.close().

        ////////////closeDB///////////
      public void CloseDB()
      {
          if(pstmt!=null)
          {
          try{
            pstmt.close();
          }catch (Exception e){
          System.out.println("can not close pstmt DB");
          e.printStackTrace();
          }
          }else if(conn!=null)
          {
          try{
            conn.close();
          }catch (Exception e){
          System.out.println("can not close conn DB");
          e.printStackTrace();
          }
          System.out.println("DB closed!");
          }
          System.gc();
      }  

Am I doing It wrongly? why I need to use finally block?
thank you, in advance.
Sahar

[Srikanth Nalam]

hello sahar,

I didn't understand the problem completely. But in your recent post i observed that you are using "else if" for closing connection. So it will be closed only if pstmt is null.

Ignore this if you are already aware of this.

[Jeanne Boyarsky]

Sahar,
The whole closeDB() method can be called from a finally block. But yes, you do need a finally block to ensure the resources are closed.

[N.Senthil Kumar]

Paul Sturrock wrote:If you do not close them the resources remain in use and quickly you will run out of available connections to your database. When you open a connection you should always close it in a finally block.

Hi ,

May i know , do we get any specific exception if the Connection are not closed or if we run out of available connections of our database, what will happen. ?


Thanks in advance.

[Jan Cumps]

Hi,

I googled "what happens if a database runs out of connections", and found out that lots of bad things can happen.
You are waisting database resources. It depends on your database flavor (and lots of other things) how it deals with the situation.
Your program may slow down, block, get exceptions...
Regards, Jan

[N.Senthil Kumar]

Thank you , Guys...

[abhi vazhakalil]

sahar sa wrote:Dear friends,
I have a problem with making and closing the connection to my data base.
let me explain, I closed my CONNECTION and PSTMT after insert query but when I run this code after the first round I get the below error :
code:
trigger code:

 DB2 DB2= new DB2(); 
 for (int i=0;i<7;i++)
 {
 DB2.insert("Celeron","Intel2",85,106,0.33,3,2.5,0.33,7,0.33);
 }

insert code:

      public static void insert(final String Name,final String Manfac, final double Pmax,
      final double Pmin,final double Pw,final double Qmax,final double Qmin,final double Qw,
      final double Deadline,final double Tw) 
    {   
        Connection conn = null;
        PreparedStatement pstmt = null;

        try{
             Connection con = getConnection();
             String insert="insert into tbuyer(name,manfac,pmax,pmin,pw,qmax,qmin,qw,deadline,tw)"
             + " values(?,?,?,?,?,?,?,?,?,?)";
             pstmt = con.prepareStatement(insert);
             pstmt.setString(1,Name);
             pstmt.setString(2,Manfac);
             pstmt.setDouble(3,Pmax);
             pstmt.setDouble(4,Pmin);
             pstmt.setDouble(5,Pw);
             pstmt.setDouble(6,Qmax);
             pstmt.setDouble(7,Qmin);
             pstmt.setDouble(8,Qw);
             pstmt.setDouble(9,Deadline);
             pstmt.setDouble(10,Tw);
             int row=pstmt.executeUpdate();
             System.out.println(row+" rows was effected");
             System.out.println("Good was inserted into DB2: Name: "+Name +", "+Manfac
             +", "+"Quality:"+Qmax+", "+Qmin+", "+Qw+" Price:"+Pmax+", "+Pmin
             +", "+Pw+" Deadline:"+Deadline+", "+Tw);
             pstmt.close();
             con.close();
        }
                    
        catch(SQLException ex)
        {
        System.out.println("SQLException: " + ex.getMessage());
        System.out.println("SQLState: " + ex.getSQLState());
        System.out.println("VendorError: " + ex.getErrorCode());
        }
        catch(Exception ex){ex.printStackTrace();}

    }

error:

SQLException: No operations allowed after connection closed.
SQLState: 08003
VendorError: 0

so according to this error I should remove closing conn and pstmt but in all the examples I found they closed them.

Can some one tell me what will happen if i do not close my CONNECTION and PSTMT after insert, delete or select?

thnx,
Sahar.

I executed this above program successfully without any exception. As whenever you are calling the insert method, you are creating a fresh connection object. So if you close connection, it does'nt matter.