Spring JdbcTemplate实例

1、常用方法

* update():执行DML语句。增、删、改语句
* queryForMap():查询结果将结果集封装为map集合，将列名作为key，将值作为value 将这条记录封装为一个map集合
         * 注意：这个方法查询的结果集长度只能是1
* queryForList():查询结果将结果集封装为list集合
         * 注意：将每一条记录封装为一个Map集合，再将Map集合装载到List集合中
  * query():查询结果，将结果封装为JavaBean对象
         * query的参数：RowMapper
           * 一般我们使用BeanPropertyRowMapper实现类。可以完成数据到JavaBean的自动封装
            * new BeanPropertyRowMapper<类型>(类型.class)
 * queryForObject：查询结果，将结果封装为对象
                * 一般用于聚合函数的查询

2、示例代码

package com.alphajuns.jdbcTest;

import com.alphajuns.pojo.User;
import com.alphajuns.utils.JDBCUtils;
import org.junit.Test;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;

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

/**
 * @ClassName JDBCTest
 * @Description
 * @Author AlphaJunS
 * @Date 2019/10/30 22:19
 * @Version V1.0
 **/
public class JDBCTest {

    private JdbcTemplate jdbcTemplate = new JdbcTemplate(JDBCUtils.getDataSource());

    @Test
    public void update1() {
        String sql = "update user set username = ? where id = ?";
        int count = jdbcTemplate.update(sql, "zhangsanfeng", 3);
        System.out.println(count);
    }

    @Test
    public void update2() {
        String sql = "insert user (id, username, password) VALUE (?, ?, ?)";
        int count = jdbcTemplate.update(sql, 6, "zhaoliu", "654321");
        System.out.println(count);
    }

    @Test
    public void query1() {
        String sql = "select * from user";
        List<Map<String, Object>> mapList = jdbcTemplate.queryForList(sql);
        for (Map<String, Object> stringObjectMap : mapList) {
            System.out.println(stringObjectMap);
        }
    }

    @Test
    public void query2() {
        String sql = "select * from user where id = ?";
        Map<String, Object> stringObjectMap = jdbcTemplate.queryForMap(sql, 4);
        System.out.println(stringObjectMap);
    }

    @Test
    public void query3() {
        String sql = "select * from user";
        List<User> userList = jdbcTemplate.query(sql, new RowMapper<User>() {
            @Override
            public User mapRow(ResultSet resultSet, int i) throws SQLException {
                User user = new User();
                user.setId(resultSet.getInt("id"));
                user.setUsername(resultSet.getString(1));
                user.setPassword(resultSet.getString("password"));
                return user;
            }
        });
        System.out.println(userList);
    }

    @Test
    public void query4() {
        String sql = "select * from user";
        List<User> userList = jdbcTemplate.query(sql, new BeanPropertyRowMapper<User>(User.class));
        System.out.println(userList);
    }

}