java 使用策略模式操作JDBC数据库

java 使用策略模式操作JDBC数据库

构造一个操作数据库的工具类，可以获得连接和释放连接

public class DBUtil {   private static Connection conn = null;   static { //静态初始块       try {         Class.forName("com.mysql.jdbc.Driver");         conn = DriverManager.getConnection("jdbc:Mysql://127.0.0.1:3306/test", "root", "064319"); //初始化获取连接       } catch (ClassNotFoundException e) {         e.printStackTrace();       } catch (sqlException e) {         e.printStackTrace();       }   }       public static void closeAll(ResultSet rs, PreparedStatement psmt, Connection conn) throws SQLException {          if(rs != null) {       rs.close();     }           if(psmt != null) {       psmt.close();     }          if(conn != null) {       conn.close();     }        }         public static Connection getConnection() {     return conn;   }         public static void getTableColumnInfoByTableName(String tableName) {     Connection conn = getConnection();     ResultSet rs = null;     PreparedStatement psmt = null;     String sql = "select * from " + tableName;     try {       psmt = conn.prepareStatement(sql);       rs = psmt.executeQuery();              ResultSetMetaData resultSetMetaData = rs.getMetaData();       for(int i = 1; i<= resultSetMetaData.getColumnCount(); i++) {         System.out.println(resultSetMetaData.getColumnName(i));       }            } catch (SQLException e) {       e.printStackTrace();     } finally {       try {         closeAll(rs, psmt, conn);       } catch (SQLException e) {         e.printStackTrace();       }     }   }         public static void getTableInfoByTableName(String tableName) {     Connection conn = getConnection();     PreparedStatement psmt = null;     ResultSet rs = null;     String sql = "select * from " + tableName;     try {       psmt = conn.prepareStatement(sql);       rs = psmt.executeQuery();              while(rs.next()) {         ResultSetMetaData resultSetMetaData = rs.getMetaData();         for(int i = 1; i<= resultSetMetaData.getColumnCount(); i++) {           if(i < resultSetMetaData.getColumnCount()) {             System.out.print(rs.getObject(resultSetMetaData.getColumnName(i)) + ", ");           } else {             System.out.print(rs.getObject(resultSetMetaData.getColumnName(i)));           }         }         System.out.println();       }          } catch (SQLException e) {       e.printStackTrace();     } finally {       try {         closeAll(rs, psmt, conn);       } catch (SQLException e) {         e.printStackTrace();       }     }   } }