Mybatis源码 Mybatis是如何与spring框架整合的

Posted 2023-02-27 Dream_it_possible！

        Mybatis是现在最流行的数据库中间件之一，用mybatis的好处在于让开发者更专注在SQL本身，能与多种数据库兼容，而spring框架又是java最强大的框架，对于java来讲，万物是基于spring 的，因此我们有必要去理解mybatis 是如何整合spring框架，如果我们理解了怎么整合spring框架，那么怎么整合springboot框架就更容易理解, 那么本文就spring 整合mybatis原理进行深度解析。

一、环境准备

应用	版本号
spring-mybatis	2.0.0
mybatis	3.5.0
jdk	1.8
mysql server	5.7
mysql-connector	5.1.17
spring-jdbc	5.1.5.RELEASE
spring-context	5.1.5.RELEASE
mybatis-spring-boot-starter	1.3.2

        github地址: GitHub - mybatis/spring: Spring integration for MyBatis 3

        首先我用spring-mybatis 实现spring应用下整合mybatis的demo, 先会用再去学习源码。

二、Spring 整合mybatis

        新建一个maven工程，不使用spring intializer创建，本篇通过注解来整合，也可以通过xml整合，工程目录:

添加依赖

在pom.xml文件里添加依赖:

    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-spring</artifactId>
            <version>2.0.0</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.17</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>5.1.5.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.1.5.RELEASE</version>
        </dependency>

    </dependencies>

配置数据源、mapper和mapper.xml

        配置数据源,   用db.properites文件记录即可:

spring.datasource.url=jdbc:mysql://localhost:3306/dev?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=Asia/Shanghai
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

        mybatis需要通过配置@MapperScan扫描接口mapper，才能创建接口的代理对象, 通过SqlSessionFactoryBean 设置dataSource和mapperLocations才能映射数据库和xml文件。

package com.example.mybatis.config;

import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
import org.springframework.jdbc.datasource.DriverManagerDataSource;

import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

/**
 * @author bingbing
 * @date 2023/2/7 0007 17:04
 */
@Configuration
@MapperScan(basePackages = "com.example.mybatis.mapper")
public class MybatisConfig 

    @Bean
    public SqlSessionFactoryBean initBean() 
        SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
        // 扫描的xml文件
        factoryBean.setMapperLocations(new Resource[]new ClassPathResource("UserMapper.xml"));
        // note running without SqlSessionFactoryBean.configLocation set => default configuration
        factoryBean.setDataSource(initDataSource());
        return factoryBean;
    

    @Bean(name = "initDataSource")
    public DataSource initDataSource() 
        Properties properties = new Properties();
        InputStream is = ClassLoader.getSystemResourceAsStream("db.properties");
        try 
            properties.load(is);
         catch (IOException e) 
            e.printStackTrace();
        
        String url = properties.getProperty("spring.datasource.url");
        String username = properties.getProperty("spring.datasource.username");
        String password = properties.getProperty("spring.datasource.password");
        String driverClassName = properties.getProperty("spring.datasource.driver-class-name");
        DriverManagerDataSource dataSource = new DriverManagerDataSource();
        dataSource.setUrl(url);
        dataSource.setUsername(username);
        dataSource.setPassword(password);
        dataSource.setDriverClassName(driverClassName);
        return dataSource;
    

启动报错:

Exception in thread "main" java.lang.NoClassDefFoundError:org/apache/ibatis/logging/LogFactory

经检查，发现缺少mybatis依赖，添加mybatis依赖:

     <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.0</version>
        </dependency>

 启动测试:

    public static void main(String[] args) 
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(MybatisConfig.class);
        context.start();
        UserMapper userMapper = context.getBean(UserMapper.class);
        Integer count = userMapper.findCountUser();
        System.out.println("userMapper:" + userMapper + ", 数量为: " + count);
    

 至此spring应用整合mybatis成功，代码附在最后。

三、Spring Boot 整合mybatis 

        新建springboot工程, 工程目录如下:

添加依赖

        核心依赖mybatis-spring-boot-starter, 注意版本与mysql-connector版本的对应关系，其实还是mybatis与mysql-connector版本的对应关系。

 <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>


        <!--mybatis整合springboot-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.3.2</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.17</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

配置数据源、xml路径和mapper

spring.datasource.url=jdbc:mysql://localhost:3306/dev?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=Asia/Shanghai
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

mybatis.mapper-locations=mapper/*.xml

 配置mapper的BasePackages:

@SpringBootApplication
@MapperScan(basePackages = "com.sh.bing.mapper")
public class SpringbootMybatisMavenApplication 

    public static void main(String[] args) 
        SpringApplication.run(SpringbootMybatisMavenApplication.class, args);
    

启动应用, 访问 http://localhost:8080/user/test