Java中的oracle数据库连接

Question

I am new to java and i have written the following:

package mypackage;
public class DBconnection {

     Connection con = null;

    public Connection getConnection() throws Exception, SQLException
    {
        try
        {
             Class.forName("oracle.jdbc.driver.OracleDriver");
             con=DriverManager.getConnection("jdbc:oracle:thin:@zzz:1521:zzz","zzz", "zzz");
        }
        catch(Exception e)
        {

        }
        return con;
    }

    public void removeConnection() throws SQLException
    {
        con.close();
    }

}

When I am accesing the above code in a jsp page i have written following:

   DBconnection dbconnect = new DBconnection();   
   dbconnect.getConnection();

I want to erite dbconnect.con.prepareStatement......("sql query here");// but error is coming as con is not public in mypackage.DBconnection ; cannot be accessed outside package

dbconnect.con is not accessible why????? I have declared variable con in public in the above code. Error is coming as con is not public in mypackage.DBconnection ; cannot be accessed outside package, how to resolve this??? please help me

Answer 1

In the code posted above, con is package visible and not public. That is why you get the message cannot be accessed outside package . To make it public you have to write

public Connection con = null;

Note that if you are just going to call

dbconnect.con.prepareStatement

you might end up with a NullPointerException , since con is only initialized in the getConnection() method. So I would advise to use the getter you created

dbconnect.getConnection().prepareStatement

Of course, the getter would need to be adjusted to only create a new connection when con is still null . Otherwise it can just return con directly. The removeConnection should then after closing the connection set con to null , otherwise calling the getConnection after calling removeConnection would return a closed connection, which is pretty useless

Answer 2

move this code to the constructor

public DBconnection(){
try
    {
         Class.forName("oracle.jdbc.driver.OracleDriver");
         con=DriverManager.getConnection("jdbc:oracle:thin:@zzz:1521:zzz","zzz", "zzz");
    }
    catch(Exception e)
    {

    }
}

then make one object of it and share it to all your application classes and when you want to use connection just call getConnecion() from his object