Question

I use the following codes to connect to Oracle’s database:

Connection conn = null;
Statement stmt = null;
ResultSet rset = null;
String jdbc_url = "jdbc:oracle:thin:hr/hr@localhost:1521:XE";
String query = "";
try {
   DriverManager.registerDriver(new oracle.jdbc.OracleDriver());
   conn = DriverManager.getConnection(jdbc_url);
   stmt = conn.createStatement();
   query = "select username " + " from users ";
   rset = stmt.executeQuery(query);

   // my codes

} catch (SQLException sqle) {
   System.out.println("result error, " + e.getMessage());
} catch (NumberFormatException nfe) {

} finally {
   try {
      rset.close();
      stmt.close();
      conn.close();

   } catch (Exception e) {
      System.out.println("Error in closing " + e.getMessage());
   }
}

Do I have to use this code in every action that I make for every query that I want? Making the connection and terminating it? Everytime?

Answer 1

You don’t have to connect every time. Just make sure you close the resultset and the statement every time. See this answer as example for a good DB wrapper class.

You can make your Connection a class variable that is initalized in the constructor. Something like this:

public class DbWrapper {
    private Connection conn = null;
    String jdbc_url="jdbc:oracle:thin:hr/hr@localhost:1521:XE";

    public DbWrapper() {
        conn=DriverManager.getConnection(jdbc_url);
    }

    public Arraylist<User> getUsers() {
         ...
    }
}