springboot学习(四)：MyBatis多数据源配置

心已赠人 2022-05-14 04:24 205阅读 0赞

# 说明 #

通过在翟永超的博客学习了多数据源的配置章节后，发现当结合实际的需求使用时还有些困难，于是找资料学习了结合mybatis的多数据源配置，在这里记录下。在学习中，使用了两个不同的mysql数据库，分别在本地和虚拟机，用来模拟不同ip的数据库，类似于分库分表后部署在不同地方的情况。

# 正文 #

本文通过使用不同的数据源，达到在不同库中查找不同的数据的目的。

## 1.项目的初始构建 ##

添加依赖

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

通过手动配置数据源，要在项目启动类中排除数据源的自动配置

@SpringBootApplication
    @EnableAutoConfiguration(exclude = {DataSourceAutoConfiguration.class})
    public class MulDatasourceApplication extends SpringBootServletInitializer { 
    
        public static void main(String[] args) {
            SpringApplication.run(MulDatasourceApplication.class, args);
        }
    }

## 2.在application.properties中添加配置 ##

#第一数据源
    datasource.first.driverClassName=com.mysql.jdbc.Driver
    datasource.first.url=jdbc:mysql://ip:3306/dataBase?characterEncoding=UTF-8
    datasource.first.username=**
    datasource.first.password=**
    
    #第二数据源
    datasource.second.driverClassName=com.mysql.jdbc.Driver
    datasource.second.url=jdbc:mysql://ip:3306/dataBase?characterEncoding=UTF-8
    datasource.second.username=**
    datasource.second.password=**

## 3.编写注解类 ##

该注解用于mybatis的查询时标注接口使用的数据源  
第一数据源 UseDatasourceFirst

@Retention(RetentionPolicy.CLASS)
    @Target(ElementType.TYPE)
    public @interface UseDatasourceFirst { 
    }

第二数据源 UseDatasourceSecond

@Retention(RetentionPolicy.CLASS)
    @Target(ElementType.TYPE)
    public @interface UseDatasourceSecond { 
    }

## 4.配置数据源 ##

第一数据源配置

@Configuration
    @MapperScan(basePackages = "com.example.mul_datasource.db.dao", annotationClass = UseDatasourceFirst.class, sqlSessionFactoryRef = FirstDatasoruceConfig.SQL_SESSION_FACTOR_NAME)
    public class FirstDatasoruceConfig { 
        public static final String SQL_SESSION_FACTOR_NAME = "sqlSessionFactoryFirst";
        public static final String TRANSACTION_MANAGER="txManagerFirst";
        protected Logger logger = LoggerFactory.getLogger(FirstDatasoruceConfig.class);
    
        @Bean(name = "datasourceFirst")
        @Primary
        @ConfigurationProperties(prefix = "datasource.first")
        public DataSource dataSourceFirst(){
            return DataSourceBuilder.create().build();
        }
    
        @Bean(name = TRANSACTION_MANAGER)
        @Primary
        public PlatformTransactionManager txManagerFirst(@Qualifier("datasourceFirst") DataSource datasourceFirst){
            return new DataSourceTransactionManager(datasourceFirst);
        }
    
        @Bean(name = FirstDatasoruceConfig.SQL_SESSION_FACTOR_NAME)
        @Primary
        public SqlSessionFactory sqlSessionFactory(@Qualifier("datasourceFirst") DataSource datasourceFirst) throws Exception {
            SqlSessionFactoryBean sessionFactoryBean = new SqlSessionFactoryBean();
            sessionFactoryBean.setDataSource(datasourceFirst);
            sessionFactoryBean.setTypeAliasesPackage("com.example.mul_datasource.db.pojo");
            Resource[] resources = new PathMatchingResourcePatternResolver()
                                   .getResources("classpath:com/example/mul_datasource/db/mapper/*Mapper.xml");
            sessionFactoryBean.setMapperLocations(resources);
            return sessionFactoryBean.getObject();
        }
    }

第二数据源配置

@Configuration
    @MapperScan(basePackages = "com.example.mul_datasource.db2.dao", annotationClass = UseDatasourceSecond.class, sqlSessionFactoryRef = SecondDatasourceConfig.SQL_SESSION_FACTORY_NAME)
    public class SecondDatasourceConfig { 
        public static final String SQL_SESSION_FACTORY_NAME = "sqlSessionFactorySecond";
        public static final String TRANSACTION_MANAGER = "txManageSecond";
        protected Logger logger = LoggerFactory.getLogger(SecondDatasourceConfig.class);
    
        @Bean(name = "datasourceSecond")
        @ConfigurationProperties(prefix = "datasource.second")
        public DataSource dataSourceSecond(){
            return DataSourceBuilder.create().build();
        }
    
        @Bean(name = SecondDatasourceConfig.TRANSACTION_MANAGER)
        public PlatformTransactionManager txManagerSecond(@Qualifier("datasourceSecond") DataSource datasourceSecond){
            return new DataSourceTransactionManager(datasourceSecond);
        }
    
        @Bean(name = SQL_SESSION_FACTORY_NAME)
        public SqlSessionFactory sqlSessionFactory(@Qualifier(value = "datasourceSecond") DataSource dataSource) throws Exception {
            SqlSessionFactoryBean sessionFactoryBean = new SqlSessionFactoryBean();
            sessionFactoryBean.setDataSource(dataSource);
            sessionFactoryBean.setTypeAliasesPackage("com.example.mul_datasource.db2.pojo");
            Resource[] resources = new PathMatchingResourcePatternResolver()
                                   .getResources("classpath:com/example/mul_datasource/db2/mapper/*Mapper.xml");
            sessionFactoryBean.setMapperLocations(resources);
            return sessionFactoryBean.getObject();
        }
    }

## 5.插件自动生成 ##

通过上篇博文的学习[《使用c3p0连接池集成mybatis及mybatis自动代码生成插件》][c3p0_mybatis_mybatis]，学习了如果使用插件自动生成代码。这里在第一个主机数据库中创建表teacher，在第二个虚机数据库中创建表student，利用插件分别生成pojo、mapper文件、mapper接口  
分别放于不同的package中，在mapper接口类上配置使用编写的注解类

@UseDatasourceFirst
    public interface TeacherMapper {
        int deleteByPrimaryKey(Integer id);
    
        int insert(Teacher record);
    
        int insertSelective(Teacher record);
    
        Teacher selectByPrimaryKey(Integer id);
    
        int updateByPrimaryKeySelective(Teacher record);
    
        int updateByPrimaryKey(Teacher record);
    }

@UseDatasourceSecond
    public interface StudentMapper {
        int deleteByPrimaryKey(Integer id);
    
        int insert(Student record);
    
        int insertSelective(Student record);
    
        Student selectByPrimaryKey(Integer id);
    
        int updateByPrimaryKeySelective(Student record);
    
        int updateByPrimaryKey(Student record);
    }

## 6.测试 ##

@Autowired
    private TeacherMapper teacherMapper;
    
    @Autowired
    private StudentMapper studentMapper;
    
    @Test
    public void testSelectFirstDatasource(){
        Teacher teacher = teacherMapper.selectByPrimaryKey(1);
        System.out.println(teacher.getId() + "--" + teacher.getTname());
    }
    
    @Test
    public void testSelectSecondDatasource(){
        Student student = studentMapper.selectByPrimaryKey(1);
        System.out.println(student.getId() + "--" + student.getUname() + "--" + student.getAge());
    }

## 问题 ##

1.  在使用自动生成代码插件时，一直只生成insert语句，原因是未设置主键
2.  数据库的权限问题
3.  在配置数据库时，使用的参数名称必须符合要求，driverClassName,url,username,password

源码地址：[https://github.com/Edenwds/springboot\_study/tree/master/mul\_datasource][https_github.com_Edenwds_springboot_study_tree_master_mul_datasource]  
参考资料：[https://github.com/mybatis/spring-boot-starter/issues/78][https_github.com_mybatis_spring-boot-starter_issues_78]

[c3p0_mybatis_mybatis]: https://blog.csdn.net/sinat_36553913/article/details/81414965
[https_github.com_Edenwds_springboot_study_tree_master_mul_datasource]: https://github.com/Edenwds/springboot_study/tree/master/mul_datasource
[https_github.com_mybatis_spring-boot-starter_issues_78]: https://github.com/mybatis/spring-boot-starter/issues/78