JAVA 数据库切换 -2 （MSSQL 连接）

public class SqlMsDataSource implements DataSource{
    
    private static SqlMsDataSource instance = new SqlMsDataSource();;
    private SqlMsDataSource() {
        
    }
    public static SqlMsDataSource getInstance() {
       
        return instance;
    }
    
    private static LinkedList<Connection> pool = new LinkedList<Connection>();
    private static  String DriverName = " ";
    private static  String url = " ";
    private static  String username = " ";
    private static  String password = " ";
    private static Logger logger = Logger.getLogger(SqlMsDataSource.class);
    private static Connection conn =null;
    static{
        try {
            ResourceBundle res = ResourceBundle.getBundle("uh");
            url = res.getString("msssql.url"); 
            username = res.getString("msssql.username");  
            password = res.getString("msssql.password"); 
            DriverName = res.getString("msssql.driver"); 
            Class.forName(DriverName);      
            Connection conn = DriverManager.getConnection(url, username, password);
            logger.info("mssql  connect successfully");
        } catch (Exception e) {
            logger.info("mssql connect fail");       
            e.printStackTrace();
            throw new RuntimeException("mssql connect fail");
        }
    }
    
    @Override
    public Connection getConnection() throws SQLException {
        
        if(conn == null || conn.isClosed()) {            
            conn = DriverManager.getConnection(url, username, password);
        }
        return conn;
    }
    

    @Override
    public PrintWriter getLogWriter() throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void setLogWriter(PrintWriter out) throws SQLException {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void setLoginTimeout(int seconds) throws SQLException {
        // TODO Auto-generated method stub
        
    }

    @Override
    public int getLoginTimeout() throws SQLException {
        // TODO Auto-generated method stub
        return 0;
    }

    @Override
    public java.util.logging.Logger getParentLogger() throws SQLFeatureNotSupportedException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public <T> T unwrap(Class<T> iface) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public boolean isWrapperFor(Class<?> iface) throws SQLException {
        // TODO Auto-generated method stub
        return false;
    }


    @Override
    public Connection getConnection(String username, String password) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

  

}