代码：

import java.sql.*;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Test {

    //执行select
    private List<Map<String, Object>> executeGet(String schema, String sql) throws SQLException {
        Statement statement = null;
        ResultSet resultSet = null;
        try {
            Connection connection = getConnection();
            connection.setCatalog(schema);
            statement = connection.createStatement();
            resultSet = statement.executeQuery(sql);
            ResultSetMetaData metaData = resultSet.getMetaData();
            List<Map<String, Object>> resultList = new ArrayList<>();
            while (resultSet.next()) {
                Map<String, Object> dataMap = new HashMap<>();
                for (int i = 1; i <= metaData.getColumnCount(); i++) {
                    dataMap.put(metaData.getColumnLabel(i), resultSet.getObject(i));
                }                resultList.add(dataMap);
            }
            return resultList;
        } catch (Exception e) {
            throw e;
        } finally {
            try {
                if (resultSet != null) {
                    resultSet.close();
                }
                if (statement != null) {
                    statement.close();
                }
            } catch (SQLException e) {

            }
        }
    }

    //执行update，insert，delete
    private int executeUpdate(String schema, String sql) throws SQLException {
        Statement statement = null;
        try {
            Connection connection = getConnection();
            connection.setCatalog(schema);
            statement = connection.createStatement();
            return statement.executeUpdate(sql);
        } catch (Exception e) {
            throw e;
        } finally {
            try {
                if (statement != null) {
                    statement.close();
                }
            } catch (SQLException e) {

            }
        }
    }

	//将结果集转换为对象
    public static <T> List<T> parserDbo(List<Map<String, Object>> dboMapList, Class<T> dboClass, boolean canEmpty) throws Exception {
        if (CollectionUtil.isEmpty(dboMapList)) {
            if (!canEmpty) {
                throw new Exception("");
            }
            dboMapList = new ArrayList<>();
        }
        List<T> resultList = new ArrayList<>();
        for (Map<String, Object> dboMap : dboMapList) {
            resultList.add(BeanUtil.mapToBean(dboMap, dboClass, false));
        }
        return resultList;
    }


}

注意：BeanUtil.mapToBean这个方法，需要导入以下依赖

    <dependency>
      <groupId>cn.hutool</groupId>
      <artifactId>hutool-all</artifactId>
      <version>5.7.4</version>
    </dependency>

一、查询

String SEARCH = "select TOK_TO from CB_TO ";
	private String getTo() {
		String to = "";
		// 建立数据库连接
		try {
			Connection connection = null;
			PreparedStatement statement = null;
			ResultSet resultSet = null;
			connection = LianaDBAccess.getConnection();
			statement = connection.prepareStatement(SEARCHTOKEN);
			resultSet = statement.executeQuery();
			if (resultSet.next()) {
				to = resultSet.getString(1);
			}
			connection.close();
		} catch (TranFailException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return to;
	}

二、更新

private boolean updateTo(String to) {
		Connection connection = null;
		// 建立数据库连接
		try {
			connection = LianaDBAccess.getConnection();
			// 执行更新语句
			LianaDBAccess.executeSQLUpdate(connection,"UPDATE CB_TO SET TO_TO='" + to + "'");
			connection.commit();
			return true;
		} catch (TranFailException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			JOptionPane.showMessageDialog(null, "更改发生异常"); 
			return false;
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			JOptionPane.showMessageDialog(null, "更改发生异常"); 
			return false;
		} finally {
			try {
				LianaDBAccess.releaseConnection(connection);
			} catch (TranFailException ex) {
				Trace.logError(Trace.COMPONENT_ACTION, "更改发生异常", ex);
				return false;
			}
		}

	}