Example - 1

In the following example, the class DatabaseConnection opens and manages a connection to a database for a J2EE application. The method openDatabaseConnection opens a connection to the database using a DriverManager to create the Connection object conn to the database specified in the string constant CONNECT_STRING.

conn = DriverManager.getConnection(CONNECT_STRING);try {} catch (SQLException ex) {...}
private static final String CONNECT_STRING = "jdbc:mysql://localhost:3306/mysqldb";private Connection conn = null;public DatabaseConnection() {}public void openDatabaseConnection() {}// Member functions for retrieving database connection and accessing database...public class DatabaseConnection {}

The use of the DriverManager class to directly manage the connection to the database violates the J2EE restriction against the direct management of connections. The J2EE application should use the web application container's resource management facilities to obtain a connection to the database as shown in the following example.

InitialContext ctx = new InitialContext();DataSource datasource = (DataSource) ctx.lookup(DB_DATASRC_REF);conn = datasource.getConnection();
try {} catch (NamingException ex) {...}} catch (SQLException ex) {...}
private static final String DB_DATASRC_REF = "jdbc:mysql://localhost:3306/mysqldb";private Connection conn = null;public DatabaseConnection() {}public void openDatabaseConnection() {}// Member functions for retrieving database connection and accessing database...public class DatabaseConnection {}