Java connecting to multiple databases

Question

I am creating a java application that connects to multiple databases. A user will be able to select the database they want to connect to from a drop down box.

The p

Answer 1

You're storing a unique datasource (and connection, and dbMainConnection) in a static variable of your class. Each time someone asks for a datasource, you replace the previous one by the new one. If an exception occurs while getting a datasource from JNDI, the static datasource stays as it is. You should not store anything in a static variable. Since your dbMainConnection class is constructed with the name of a database, and there are several database names, it makes no sense to make it a singleton.

Just use the following code to access the datasource:

public final class DataSourceUtil {
    /**
     * Private constructor to prevent unnecessary instantiations
     */
    private DataSourceUtil() {
    }

    public static DataSource getDataSource(String name) {
        try {
            Context ctx = new InitialContext();
            String database = "jdbc/" + name;
            return (javax.sql.DataSource) ctx.lookup (database);
        }
        catch (NamingException e) {
            throw new IllegalStateException("Error accessing JNDI and getting the database named " + name);
        }
    }
}

And let the callers get a connection from the datasource and close it when they have finished using it.