Database declaration

[simontkk2005]

hi..i `m still new to database connection

i would like to know,is there any way to declare the connection of database in a class.

when i need the connection in others class,then i might be able to call it out.and without redeclare it again in new class.

thx

[r035198x]

Google DAO layer.

[roy.jaffray]

Book is by Gregory D. Speegle .. very good .. very flexible



import java.sql.*;

public class ConnectionJDBC {

public Connection makeConnection()
throws SQLException {
try {
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
} catch (ClassNotFoundException e) {
throw new SQLException("Unable to load driver class");
}
return DriverManager.getConnection("jdbc:odbc:jdbc_book") ;
}

public Connection makeConnection(String URL)
throws SQLException {
return DriverManager.getConnection(URL);
}

public Connection makeConnection(String DriverName, String URL)
throws SQLException {
try {
Class.forName(DriverName);
} catch (ClassNotFoundException e) {
throw new SQLException("Unable to load driver class");
}
return DriverManager.getConnection(URL);
}

public Connection makeConnection(String URL, String username,
String password)
throws SQLException {
return DriverManager.getConnection(URL,username,password) ;
}

public Connection makeConnection(String DriverName, String URL,
String username, String password)
throws SQLException {
try {
Class.forName(DriverName);
} catch (ClassNotFoundException e) {
throw new SQLException("Unable to load driver class");
}
return DriverManager.getConnection(URL,username,password) ;
}

public void closeConnection(Connection c, Statement s)
{
try {
if (s != null) s.close();
if (c != null) c.close();
} catch (SQLException sqlex) {}
}

public static void main(String args[]) {
ConnectionJDBC CJ = new ConnectionJDBC();
Connection dbConnect = null;
Statement dbStatement = null;
try {
switch (args.length) {
case 0 : dbConnect = CJ.makeConnection();
break;
case 1 : dbConnect = CJ.makeConnection(args[0]);
break;
case 2 : dbConnect = CJ.makeConnection(args[0],args[1]);
break;
case 3 : dbConnect = CJ.makeConnection(args[0],args[1],args[2]);
break;
case 4 : dbConnect = CJ.makeConnection(args[0],args[1],args[2],
args[3]);
break;
default :
System.out.println("Using the default driver");
dbConnect = CJ.makeConnection();
}
System.out.println("Made a connection!");
dbStatement = dbConnect.createStatement();
System.out.println("Made a statement!");
} catch (SQLException sqlex) {
System.out.println(sqlex.getMessage());
}
finally {
CJ.closeConnection(dbConnect,dbStatement);
System.out.println("Closed the connection.");
}
}
}


import java.sql.*;

public class SimpleJDBC extends ConnectionJDBC {
public static void main(String args[]) {
if (args.length != 1) {
System.out.println("Usage: java SimpleJDBC custid");
System.exit(1);
}

String query = "Select Title, Type " +
"from Orders O, Titles T, Tapes V " +
"where V.TapeId=O.TapeId and T.TitleId=V.TitleId and " +
"Status = 'O' and " +
"O.CustomerID= " + args[0];

SimpleJDBC J = new SimpleJDBC();
Connection dbConnect = null;
Statement dbStatement = null;
ResultSet dbRS = null;
try {
dbConnect = J.makeConnection(); //from ConnectionJDBC
dbStatement = dbConnect.createStatement();
dbRS = dbStatement.executeQuery(query);
J.presentResultSet(dbRS);
} catch (SQLException sqlex) {
System.out.println(sqlex.getMessage());
} finally {
J.closeConnection(dbConnect,dbStatement); //from ConnectionJDBC
}
}

public void presentResultSet(ResultSet rs)
throws SQLException {
if (!rs.next()) System.out.println("No records for customer");
else {
do {
System.out.println(rs.getString("Title") + ": " +
rs.getString("Type"));
} while (rs.next());
}
}
}

[Tolls]

Not terribly impressed.

He doesn't use bind variables (ie a PreparedStatement), and even worse he doesn't close the result set in the finally block. Assuming the result set will be closed on closing the statement is poor practice.

[raqman]

Hi.
Try to Google "Database Connection Classes".