SpringBoot重点详解--使用MyBatis操作多数据源

ゝ一世哀愁。 2022-05-26 13:25 213阅读 0赞

**目录**

添加依赖与配置

配置数据源

定义Mapper

使用Mapper

启动类测试

--------------------

本文将对如何使用Springboot+MyBatis操作多数据源进行简单示例和介绍，项目的完整目录层次如下图所示。

![70][]

# 添加依赖与配置 #

首先，需要在工程POM文件中引入MyBatis和MySQL的Maven依赖。

<parent>
    		<groupId>org.springframework.boot</groupId>
    		<artifactId>spring-boot-starter-parent</artifactId>
    		<version>1.4.1.RELEASE</version>
    	</parent>
    	<dependencies>
    		
    		<dependency>
    			<groupId>org.mybatis.spring.boot</groupId>
    			<artifactId>mybatis-spring-boot-starter</artifactId>
    			<version>1.2.0</version>
    		</dependency>
    		
    		<dependency>
    			<groupId>mysql</groupId>
    			<artifactId>mysql-connector-java</artifactId>
    		</dependency>
    	</dependencies>

其中mybatis-spring-boot-starter是 MyBatis 官方提供的Starter， 其Github 源码地址: [https://github.com/mybatis/spring-boot-starter][https_github.com_mybatis_spring-boot-starter] 。

此外，mybatis-spring-boot-stater 的官方文档地址：[http://www.mybatis.org/spring-boot-starter/][http_www.mybatis.org_spring-boot-starter]，MyBatis 官方中文文档地址：[http://www.mybatis.org/mybatis-3/zh/java-api.html][http_www.mybatis.org_mybatis-3_zh_java-api.html] 。

然后，在核心配置文件application.properties中添加数据源相关配置。

#########################################################
    ### Primary DataSource -- DataSource 1 configuration  ###
    #########################################################
    primary.datasource.url=jdbc:mysql://localhost:3306/dev1?useUnicode=true&characterEncoding=utf8
    primary.datasource.driverClassName=com.mysql.jdbc.Driver
    primary.datasource.username=root
    primary.datasource.password=123456
    
    #########################################################
    ### Secondary DataSource -- DataSource 2 configuration ##
    #########################################################
    secondary.datasource.url=jdbc:mysql://localhost:3306/dev2?useUnicode=true&characterEncoding=utf8
    secondary.datasource.driverClassName=com.mysql.jdbc.Driver
    secondary.datasource.username=root
    secondary.datasource.password=123456

# 配置数据源 #

首先，分别为每一个数据源各定义一个配置类，在配置类中通过注解@MapperScan来为不同包下的Mapper分别创建不同SqlSessionFactory、SqlSessionTemplate和DataSourceTransactionManager，用来操作不同的数据源。

/**
     * 数据源 1 配置类
     */
    @Configuration
    @MapperScan(basePackages = "com.pengjunlee.primary.mapper", sqlSessionTemplateRef = "primarySqlSessionTemplate")
    public class PrimaryDataSourceConfig {
    
    	@Bean(name = "primaryDataSource")
    	@ConfigurationProperties(prefix = "primary.datasource")
    	public DataSource primaryDataSource() {
    		return DataSourceBuilder.create().build();
    	}
    
    	@Bean
    	@ConfigurationProperties(prefix = "primary.datasource")
    	@Primary
    	public DataSource createDataSource() {
    		return DataSourceBuilder.create().build();
    	}
    
    	@Primary
    	@Bean(name = "primarySqlSessionFactory")
    	public SqlSessionFactory primarySqlSessionFactory(@Qualifier("primaryDataSource") DataSource dataSource)
    			throws Exception {
    		SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
    		bean.setDataSource(dataSource);
    		bean.setMapperLocations(
    				new PathMatchingResourcePatternResolver().getResources("classpath:mybatis/mapper/primary/*.xml"));
    		return bean.getObject();
    	}
    
    	@Primary
    	@Bean(name = "primaryTransactionManager")
    	public DataSourceTransactionManager primaryTransactionManager(
    			@Qualifier("primaryDataSource") DataSource dataSource) {
    		return new DataSourceTransactionManager(dataSource);
    	}
    
    	@Primary
    	@Bean(name = "primarySqlSessionTemplate")
    	public SqlSessionTemplate primarySqlSessionTemplate(
    			@Qualifier("primarySqlSessionFactory") SqlSessionFactory sqlSessionFactory) throws Exception {
    		return new SqlSessionTemplate(sqlSessionFactory);
    	}
    
    }

/**
     * 数据源 2 配置类
     */
    @Configuration
    @MapperScan(basePackages = "com.pengjunlee.secondary.mapper", sqlSessionTemplateRef = "secondarySqlSessionTemplate")
    public class SecondaryDataSourceConfig {
    
    	@Bean(name = "secondaryDataSource")
    	@ConfigurationProperties(prefix = "secondary.datasource")
    	public DataSource secondaryDataSource() {
    		return DataSourceBuilder.create().build();
    	}
    
    	@Bean(name = "secondarySqlSessionFactory")
    	public SqlSessionFactory secondarySqlSessionFactory(@Qualifier("secondaryDataSource") DataSource dataSource)
    			throws Exception {
    		SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
    		bean.setDataSource(dataSource);
    		bean.setMapperLocations(
    				new PathMatchingResourcePatternResolver().getResources("classpath:mybatis/mapper/secondary/*.xml"));
    		return bean.getObject();
    	}
    
    	@Bean(name = "secondaryTransactionManager")
    	public DataSourceTransactionManager secondaryTransactionManager(
    			@Qualifier("secondaryDataSource") DataSource dataSource) {
    		return new DataSourceTransactionManager(dataSource);
    	}
    
    	@Bean(name = "secondarySqlSessionTemplate")
    	public SqlSessionTemplate secondarySqlSessionTemplate(
    			@Qualifier("secondarySqlSessionFactory") SqlSessionFactory sqlSessionFactory) throws Exception {
    		return new SqlSessionTemplate(sqlSessionFactory);
    	}
    
    }

# 定义Mapper #

由于注解@MapperScan是通过包名来区分哪些Mapper用来操作哪个数据源，故而需要将不同数据源的Mapper接口类定义在不同的包中。

此处为了示例，定义了User（用户）和Department（部门）两个实体类，分别对应数据源一和数据源二。

/**
     * 用户
     */
    public class User {
    
    	private Long id;
    
    	private String name;
    
    	private Integer age;
    
    	// 此处省略get和set方法
    }

/**
     * 部门
     */
    public class Department {
    
    	private Long id;
    
    	private String name;
    
    	// 此处省略get和set方法
    
    }

package com.pengjunlee.primary.mapper;
    
    import org.apache.ibatis.annotations.Mapper;
    import org.apache.ibatis.annotations.Param;
    
    import com.pengjunlee.bean.User;
    
    /**
     * 数据源 1 Mapper
     */
    @Mapper
    public interface UserMapper {
    
    	User selectById(@Param("id") Long id);
    
    	void deleteById(@Param("id") Long id);
    }

package com.pengjunlee.secondary.mapper;
    
    import org.apache.ibatis.annotations.Mapper;
    import org.apache.ibatis.annotations.Param;
    import com.pengjunlee.bean.Department;
    
    /**
     * 数据源 2 Mapper
     */
    @Mapper
    public interface DepartmentMapper {
    
    	Department selectById(@Param("id") Long id);
    
    	void deleteById(@Param("id") Long id);
    }

注意：在定义Mapper接口的时候，其所在包一定要与配置文件中指定的包路径一致。

# 使用Mapper #

在实际项目中我们一般都会将定义好的Mapper自动装配到Service层进行调用，此时要格外注意事务。

以使用UserMapper为例，UserService接口定义如下。

public interface UserService {
    
    	// 根据主键查询用户
    	User getUserById(Long id);
    
    	// 根据主键删除用户
    	void deleteUserById(Long id);
    }

在接口实现类UserServiceImpl中自动装配UserMapper来完成对数据源1的操作。

@Service("userService")
    public class UserServiceImpl implements UserService {
    
    	@Autowired
    	private UserMapper userMapper;
    
    	@Override
    	public User getUserById(Long id) {
    		return userMapper.selectById(id);
    	}
    
    	@Override
    	@Transactional("primaryTransactionManager")// 注意事务
    	public void deleteUserById(Long id) {
    		userMapper.deleteById(id);
    		throw new RuntimeException();
    	}
    
    }

# 启动类测试 #

在启动类中进行测试，测试代码如下。

@SpringBootApplication
    public class MyApplication {
    
    	public static void main(String[] args) {
    		ConfigurableApplicationContext context = SpringApplication.run(MyApplication.class, args);
    
    		UserMapper userMapper = context.getBean(UserMapper.class);
    		User user = userMapper.selectById(3L);
    		System.out.println(user.getName());
    
    		DepartmentMapper deptMapper = context.getBean(DepartmentMapper.class);
    		Department dept = deptMapper.selectById(2L);
    		System.out.println(dept.getName());
    
    		// 通过删除操作测试事务
    		// DepartmentService deptService =
    		// context.getBean(DepartmentService.class);
    		// deptService.deleteDepartmentById(2L);
    
    		UserService userService = context.getBean(UserService.class);
    		userService.deleteUserById(3L);
    	}
    }

启动程序，各数据源中的数据都能查询成功且支持事务。

本文项目源码已上传至CSDN，资源地址：[https://download.csdn.net/download/pengjunlee/10612419][https_download.csdn.net_download_pengjunlee_10612419]

[70]: /images/20220526/b8c97a5628cd4b86950e0240f54ebd44.png
[https_github.com_mybatis_spring-boot-starter]: https://github.com/mybatis/spring-boot-starter
[http_www.mybatis.org_spring-boot-starter]: http://www.mybatis.org/spring-boot-starter/
[http_www.mybatis.org_mybatis-3_zh_java-api.html]: http://www.mybatis.org/mybatis-3/zh/java-api.html
[https_download.csdn.net_download_pengjunlee_10612419]: https://download.csdn.net/download/pengjunlee/10612419