Java连接Oracle数据库并查询

public class DbConn {
  private static String driver = "oracle.jdbc.driver.OracleDriver";
  private static String url = "jdbc:oracle:thin:@localhost:1521:orcl";
  private static String user = "root";
  private static String password = "root";
  private static Connection conn = null;
  static {
    try {
      Class.forName(driver);
      Log.logD("------加载驱动成功-----");
      conn = (Connection) DriverManager.getConnection(url, user, password);
      Log.logD("------连接成功-----");
    } catch (ClassNotFoundException e) {
      Log.logD("------加载驱动失败，驱动类未找到------");
      e.printStackTrace();
    } catch (SQLException e) {
      e.printStackTrace();
      Log.logD("------加载驱动失败------");
    }
  }
   public static Connection getConn(){
     return conn;
   }
}

public class DbGetCan {
  private static PreparedStatement pstmt;
  private static ResultSet rs;
  private static Connection conn;
  public static String select(String sql) {
    conn=DbConn.getConn();
    try {
      pstmt = conn.prepareStatement(sql);
      rs = pstmt.executeQuery();
      return getJsonArray();
    } catch (SQLException e) {
      e.printStackTrace();
    } catch (JSONException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
    return null;
  }
  /*
   * 将查询结果转化为json数组 需要导入Json jar包
   */
  public static String getJsonArray() throws SQLException, JSONException {
    JSONArray jsonArray=new JSONArray();
    ResultSetMetaData metaData = (ResultSetMetaData) rs.getMetaData();
    int columnCount = metaData.getColumnCount();
    while (rs.next()) {
      JSONObject jsonData = new JSONObject();
      for (int i = 1; i <= columnCount; i++) {
        String columnName = metaData.getColumnLabel(i);
        String value = rs.getString(columnName);
        jsonData.put(columnName, value);
      }
      jsonArray.put(jsonData);
    }
    rs.close();
    pstmt.close();
    return jsonArray.toString();
  }
}

//调用
String sql="select * from table";
String result=DbGetGps.select(sql);
System.out.println(result);