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);
     }

 }