Spring-JDBC使用

1. 简介

Spring框架对JDBC进行封装，使用JdbcTemplate类方便实现对数据库操作

2. 准备工作

1. 搭建子模块：spring-jdbc-tx
2. 加入依赖：

<!--spring jdbc  Spring 持久化层支持jar包-->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-jdbc</artifactId>
    <version>6.0.2</version>
</dependency>
<!-- MySQL驱动 -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.30</version>
</dependency>
<!-- 数据源 -->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <version>1.2.15</version>
</dependency>

3. 创建jdbc.properties

jdbc.user=root
jdbc.password=root
jdbc.url=jdbc:mysql://localhost:3306/spring?characterEncoding=utf8&useSSL=false
jdbc.driver=com.mysql.cj.jdbc.Driver

4. 配置Spring的配置文件 beans.xml:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context.xsd">

    <!-- 导入外部属性文件 -->
    <context:property-placeholder location="classpath:jdbc.properties" />

    <!-- 配置数据源 -->
    <bean id="druidDataSource" class="com.alibaba.druid.pool.DruidDataSource">
        <property name="url" value="${jdbc.url}"/>
        <property name="driverClassName" value="${jdbc.driver}"/>
        <property name="username" value="${jdbc.user}"/>
        <property name="password" value="${jdbc.password}"/>
    </bean>

    <!-- 配置 JdbcTemplate -->
    <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
        <!-- 装配数据源 -->
        <property name="dataSource" ref="druidDataSource"/>
    </bean>

</beans>

5. 准备数据库与测试表

CREATE DATABASE `springdb`;

use `springdb`;

CREATE TABLE `t_emp` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(20) DEFAULT NULL COMMENT '姓名',
  `age` int(11) DEFAULT NULL COMMENT '年龄',
  `sex` varchar(2) DEFAULT NULL COMMENT '性别',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

2. 实现CURD

2.1 创建测试类

创建测试类JDBCTemplateTest，整合JUnit，注入JdbcTemplate:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;

@SpringJUnitConfig(locations = "classpath:beans.xml")
public class JDBCTemplateTest {

    @Autowired
    private JdbcTemplate jdbcTemplate;
    
}

2.2 测试增删改功能

@Test
//测试增删改功能
public void testUpdate(){
    //添加功能
	String sql = "insert into t_emp values(null,?,?,?)";
	int result = jdbcTemplate.update(sql, "张三", 23, "男");
    
    //修改功能
	//String sql = "update t_emp set name=? where id=?";
    //int result = jdbcTemplate.update(sql, "张三jack", 1);

    //删除功能
	//String sql = "delete from t_emp where id=?";
	//int result = jdbcTemplate.update(sql, 1);
}

2.3 查询数据返回对象

1. 创建Emp类：

public class Emp {

    private Integer id;
    private String name;
    private Integer age;
    private String sex;

    //生成get和set方法
    //......

    @Override
    public String toString() {
        return "Emp{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", sex='" + sex + '\'' +
                '}';
    }
}

2. 查询单个对象：

//查询：返回对象
@Test
public void testSelectObject() {
    //写法一
//        String sql = "select * from t_emp where id=?";
//        Emp empResult = jdbcTemplate.queryForObject(sql,
//                (rs, rowNum) -> {
//                    Emp emp = new Emp();
//                    emp.setId(rs.getInt("id"));
//                    emp.setName(rs.getString("name"));
//                    emp.setAge(rs.getInt("age"));
//                    emp.setSex(rs.getString("sex"));
//                    return emp;
//                }, 1);
//        System.out.println(empResult);

    //写法二
    String sql = "select * from t_emp where id=?";
    Emp emp = jdbcTemplate.queryForObject(sql,
                  new BeanPropertyRowMapper<>(Emp.class),1);
    System.out.println(emp);
}

2.4 查询数据返回list集合

@Test
//查询多条数据为一个list集合
public void testSelectList(){
    String sql = "select * from t_emp";
    List<Emp> list = jdbcTemplate.query(sql, new BeanPropertyRowMapper<>(Emp.class));
    System.out.println(list);
}

2.5 查询返回单个的值

@Test
//查询单行单列的值
public void selectCount(){
    String sql = "select count(id) from t_emp";
    Integer count = jdbcTemplate.queryForObject(sql, Integer.class);
    System.out.println(count);
}