//先获取jdbc连接
            Connection connection = DriverManager.getConnection(JDBCUrl);
//从conn中获取数据库的元数据
            DatabaseMetaData databaseMetaData = connection.getMetaData();
            //库信息
//连接的库名
            System.out.println(connection.getCatalog());
//数据库类型 MYSQL ORACLE
            System.out.println(databaseMetaData.getDatabaseProductName());
//数据库版本号 8.0.15
            System.out.println(databaseMetaData.getDatabaseProductVersion());
//数据库大版本 8
            System.out.println(databaseMetaData.getDatabaseMajorVersion());
//jdbc连接的url
            System.out.println(databaseMetaData.getURL());
            System.out.println("数据库中使用的表类型");
            String[] types = { "TABLE" };
            //获取所有表
            ResultSet rs = databaseMetaData.getTables(connection.getCatalog(), null, null, null);
            while (rs.next()) {
                String tableName = rs.getString("TABLE_NAME"); //表名
                String tableType = rs.getString("TABLE_TYPE"); //表类型
                String remarks = rs.getString("REMARKS"); //表备注
                System.out.println("表名："+tableName + "   表类型： " + tableType + "   表注释：" + remarks);
                //表元数据
                ResultSetMetaData resultSetMetaData = rs.getMetaData();
//遍历表所有元数据信息
                for (int i = 1; i <=  resultSetMetaData.getColumnCount(); i++) {
                    System.out.println(rs.getString(i)+"-==-"+ resultSetMetaData.getColumnName(i));
                //表字段信息
                ResultSet resultSet = databaseMetaData.getColumns(connection.getCatalog(),databaseMetaData.getUserName(),tableName,null);
                while (resultSet.next()){
//遍历表字段所有元数据
                    for (int i = 0; i < resultSet.getMetaData().getColumnCount(); i++) {
                        System.out.println(resultSet.getMetaData().getColumnName(i+1)+":"+resultSet.getString(i+1));
                    System.out.println(resultSet.getString("TABLE_NAME")//表名
                            +"-"+resultSet.getString("column_name")//字段名
                            +"-"+resultSet.getString("TYPE_NAME")//字段类型
                            +"-"+resultSet.getString("DATA_TYPE")//字段类型
                            +"-"+resultSet.getString("COLUMN_SIZE")//长度
                            +"-"+resultSet.getString("DECIMAL_DIGITS")//长度
                            +"-"+resultSet.getString("COLUMN_DEF")//默认值
                            +"-"+resultSet.getString("REMARKS")//注释
                            +"-"+resultSet.getString("ORDINAL_POSITION")//字段位置
                            +"-"+resultSet.getString("IS_AUTOINCREMENT"));//是否自增
//获取表主键
                ResultSet rs2 = connection.getMetaData().getPrimaryKeys(connection.getCatalog(), null, tableName);
                ResultSetMetaData resultSetMetaData2 = rs2.getMetaData();
                while (rs2.next()){
                        System.out.println("主键："+rs2.getString("COLUMN_NAME"));