JAVA中直接执行sql语句示例

最新推荐文章于 2025-03-06 10:44:00 发布

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本文档展示了如何使用Java进行SQL查询（包括SELECT, UPDATE, INSERT, DELETE），并介绍如何将ResultSet转换为对象实例。重点讲解了使用PreparedStatement和连接数据库的方法，以及Hutool工具库在数据映射过程中的应用。

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>