JDBC工具类实例

System.properties配置文件（放在src下面）

driver=com.microsoft.sqlserver.jdbc.SQLServerDriver

 url=jdbc:sqlserver://localhost:1433;DatabaseName=mp

 username=sa

 password=sa

 

JDBC连接工具类（单例模式）

public final class JdbcUtilsSing {

    private String url = "jdbc:mysql://localhost:3306/jdbc";

    private String user = "root";

    private String password = "";

    // private static JdbcUtilsSing instance = new JdbcUtilsSing();

    private static JdbcUtilsSing instance = null;

    private JdbcUtilsSing() {

    }

 

    public static JdbcUtilsSing getInstance() {

       if (instance == null) {

           synchronized (JdbcUtilsSing.class) {

              if (instance == null) {

                  instance = new JdbcUtilsSing();

              }

           }

       }

       return instance;

    }

 

    static {

       try {

           Class.forName("com.mysql.jdbc.Driver");

       } catch (ClassNotFoundException e) {

           throw new ExceptionInInitializerError(e);

       }

    }

 

    public Connection getConnection() throws SQLException {

       return DriverManager.getConnection(url, user, password);

    }

 

    public void free(ResultSet rs, Statement st, Connection conn) {

       try {

           if (rs != null)

              rs.close();

       } catch (SQLException e) {

           e.printStackTrace();

       } finally {

           try {

              if (st != null)

                  st.close();

           } catch (SQLException e) {

              e.printStackTrace();

           } finally {

              if (conn != null)

                  try {

                     conn.close();

                  } catch (SQLException e) {

                     e.printStackTrace();

                  }

           }

       }

    }

}