javaee spring jdbc 查询方法

javaee spring jdbc 查询方法

package com.test.dao.impl;

import com.test.dao.IUsersDao;
import com.test.pojo.Users;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.stereotype.Component;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;

/**
 * @description:
 * @projectName:testspring2
 * @see:com.test.dao.impl
 * @author:123
 * @createTime:2023/8/28 21:56
 */
@Component
public class UsersDao implements IUsersDao {

    //注入jdbcTemplate对象
    @Autowired
    private JdbcTemplate jdbcTemplate;

    @Override
    public void add(Users user) {
        String sql = "insert into users values(null,?,?)";

        jdbcTemplate.update(sql, user.getName(), user.getPassword());
    }

    //查询 返回单个对象
    public int selectUsersCount() {
        String sql = "select count(*) from users";

        int num = jdbcTemplate.queryForObject(sql, Integer.class);

        return num;
    }

    //查询  返回集合
    public List<Users> selectUsers() {
        String sql = "select * from users";

        List<Users> usersList= jdbcTemplate.query(sql, new RowMapper<Users>() {

            //遍历结果集 将结果集中的每条数据 组装成Users对象
            @Override
            public Users mapRow(ResultSet resultSet, int i) throws SQLException {
                return rowMapHander(resultSet);
            }
        });

        return usersList;
    }

    public Users rowMapHander(ResultSet resultSet) throws SQLException {
        Users user=new Users();
        user.setId(resultSet.getInt("id"));
        user.setName(resultSet.getString("name"));
        user.setPassword(resultSet.getString("password"));
        return user;
    }
}