Spring boot 整合Mybatis 【springboot整合持久层技术系列】

墨蓝 2022-11-30 01:32 201阅读 0赞

# 前言： #

前面一篇文章讲了Spring Boot中最简单的数据持久化方案JdbcTemplate，JdbcTemplate虽然简单，但是用的并不多，因为它没有MyBatis方便，在Spring+SpringMVC中整合MyBatis步骤还是有点复杂的，要配置多个Bean，Spring Boot中对此做了进一步的简化，使MyBatis基本上可以做到开箱即用，本文就来看看在Spring Boot中MyBatis要如何使用

** 同样导入Maven依赖**

注意：mysql版本不能过低，可以看一下自己电脑中的mysql版本

<dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>druid-spring-boot-starter</artifactId>
        <version>1.1.23</version>
    </dependency>
    
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-jdbc</artifactId>
        <version>5.2.7.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.19</version>
    </dependency>
    <dependency>
        <groupId>org.mybatis.spring.boot</groupId>
        <artifactId>mybatis-spring-boot-starter</artifactId>
        <version>2.1.3</version>
    </dependency>

**创建一个User实体类**：

package com.example.demo.pojo;
    
    public class User {
        private Integer id;
        private String username;
        private String address;
    
        public Integer getId() {
            return id;
        }
    
        public void setId(Integer id) {
            this.id = id;
        }
    
        public String getUsername() {
            return username;
        }
    
        public void setUsername(String username) {
            this.username = username;
        }
    
        public String getAddress() {
            return address;
        }
    
        public void setAddress(String address) {
            this.address = address;
        }
    
        public User() {
        }
    
        @Override
        public String toString() {
            return "User{" +
                    "id=" + id +
                    ", username='" + username + '\'' +
                    ", address='" + address + '\'' +
                    '}';
        }
    }

**配置数据源：**

spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
    spring.datasource.username=root
    spring.datasource.password=123
    spring.datasource.url=jdbc:mysql://localhost:3306/ssmbuild?characterEncoding=utf-8&useSSL=false&serverTimezone=UTC

**UserMapper**

package com.example.demo.mapper;
    
    import com.example.demo.pojo.User;
    import org.apache.ibatis.annotations.Mapper;
    
    import java.util.List;
    
    @Mapper
    public interface UserMapper {
    
            List<User> getUserList();
    }

**UserMapper.xml **

<?xml version="1.0" encoding="utf-8" ?>
    <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
    <mapper namespace="com.example.demo.mapper.UserMapper">
        <select id="getUserList" resultType="com.example.demo.pojo.User" >
            select * from user
        </select>
    
    </mapper>

**测试类：**

@SpringBootTest
    class DemoApplicationTests {
    
        @Autowired
        UserMapper userMapper;
    
        @Test
        void contextLoads() {
            List<User> userList=userMapper.getUserList();
            System.out.println(userList);
        }
    }

**我们可以将mapper.xml文件放在不同位置上：**

*  位置一：

UserMapper和UserMapper.xml文件放在同一个文件下：

![20200822161937285.png][]

**但是这个时候默认下会出现一个问题：**

**生成的target文件中扫描不到UserMapper.xml文件，因为xml文件推荐是放在resource下的，所以这个时候我们需要在pom文件中**

**添加配置**

<resources>
        <resource>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</include>
            </includes>
            <filtering>false</filtering>
        </resource>
        <resource>
            <directory>src/main/resources</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</include>
            </includes>
            <filtering>false</filtering>
        </resource>
    </resources>

*   位置二：

我们在resource下把xml文件放在目录一致的位置，即可（注意： 他们的目录结构都是一样的，这样就 可以匹配到）

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMwNjMxMDYz_size_16_color_FFFFFF_t_70][]

*  位置三：

**如果我们想把mapper.xml文件随便放在resources下，我们需要在.properties文件中添加mapper文件映射**

mybatis.mapper-locations=classpath:/mapper/*.xml

这样我们就可以扫描到了

[20200822161937285.png]: /images/20221124/91e2f43aae4b47abb439f2cc4891dd66.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMwNjMxMDYz_size_16_color_FFFFFF_t_70]: /images/20221124/a29b9d9bb033494a994d1578e47d1b0e.png