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);