JAVA 数据库切换 -1 （MYSQL 连接）后续加锁

public class SqlMyDataSource implements DataSource{
    
    private static SqlMyDataSource instance = new SqlMyDataSource();
    private SqlMyDataSource() {
        
    }
    public static SqlMyDataSource getInstance() {
       
        return instance;
    }
    
    private static LinkedList<Connection> pool = new LinkedList<Connection>();
    private static  String DriverName = "com.mysql.jdbc.Driver";
    private static  String url = "";
    private static  String username = "";
    private static  String password = "";
    private static Connection conn = null;
    private static Logger logger = Logger.getLogger(SqlMyDataSource.class);
    
    static{
        try {
                         
                ResourceBundle res = ResourceBundle.getBundle("uh");
                url = res.getString("mysql.url"); 
                username = res.getString("mysql.username");  
                password = res.getString("mysql.password"); 
                DriverName = res.getString("mysql.driver"); 
                Class.forName(DriverName);              
                conn = DriverManager.getConnection(url, username, password);                                
            logger.info("mysql connect successfully");      
        } catch (Exception e) {
            logger.info("mysql connect fail");       
            e.printStackTrace();
            throw new RuntimeException("mysql 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;
    }

  

}