在使用 Spring Boot 和 MyBatis 动态切换数据源时遇到的问题以及解决方法

时间:2021-08-29 04:34:24

相关项目地址:https://github.com/helloworlde/SpringBoot-DynamicDataSource

1. org.apache.ibatis.binding.BindingException: Invalid bound statement (not found)

在使用了动态数据源后遇到了该问题,从错误信息来看是因为没有找到 *.xml 文件而导致的,但是在配置文件中
确实添加了相关的配置,这种错误的原因是因为设置数据源后没有设置SqlSessionFactoryBeantypeAliasesPackage
mapperLocations属性或属性无效导致的;

  • 解决方法:

如果在应用的入口类中添加了 @SpringBootApplication(exclude = DataSourceAutoConfiguration.class),
DataSourceConfigure类的中设置相关属性:

    @Bean
@ConfigurationProperties(prefix = "mybatis")
public SqlSessionFactoryBean sqlSessionFactoryBean() {
SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
sqlSessionFactoryBean.setDataSource(dynamicDataSource());
return sqlSessionFactoryBean;
}

或者直接配置(不推荐该方式):

    @Bean
public SqlSessionFactoryBean sqlSessionFactoryBean() {
SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
sqlSessionFactoryBean.setTypeAliasesPackage("typeAliasesPackage");
sqlSessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("mapperLocations"));
sqlSessionFactoryBean.setDataSource(dynamicDataSource());
return sqlSessionFactoryBean;
}

2. Consider marking one of the beans as @Primary, updating the consumer to accept multiple beans, or using @Qualifier to identify the bean that should be consumed

该异常在错误信息中已经说的很清楚了,是因为有多个 DataSource 的实例,所以无法确定该引用那个实例

  • 解决方法:

为数据源的某个 Bean 添加 @Primary 注解,该 Bean 应当是通过 DataSourceBuilder.create().build()
得到的 Bean,而不是通过 new AbstractRoutingDataSource 的子类实现的 Bean,在本项目中可以是 master()
slave() 得到的 DataSource,不能是 dynamicDataSource() 得到的 DataSource

3. 通过注解方式动态切换数据源无效

  • 请确认注解没有放到 DAO 层方法上, 因为会在 Service 层开启事务,所以当注解在 DAO 层时不会生效
  • 请确认以下 Bean 正确配置:
    @Bean("dynamicDataSource")
public DataSource dynamicDataSource() {
DynamicRoutingDataSource dynamicRoutingDataSource = new DynamicRoutingDataSource();
Map<Object, Object> dataSourceMap = new HashMap<>(2);
dataSourceMap.put("master", master());
dataSourceMap.put("slave", slave());

// Set master datasource as default
dynamicRoutingDataSource.setDefaultTargetDataSource(master());
// Set master and slave datasource as target datasource
dynamicRoutingDataSource.setTargetDataSources(dataSourceMap);

// To put datasource keys into DataSourceContextHolder to judge if the datasource is exist
DynamicDataSourceContextHolder.dataSourceKeys.addAll(dataSourceMap.keySet());
return dynamicRoutingDataSource;
}

@Bean
@ConfigurationProperties(prefix = "mybatis")
public SqlSessionFactoryBean sqlSessionFactoryBean() {
SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
// Here is very important, if don't config this, will can't switch datasource
// put all datasource into SqlSessionFactoryBean, then will autoconfig SqlSessionFactory
sqlSessionFactoryBean.setDataSource(dynamicDataSource());
return sqlSessionFactoryBean;
}

4. @Transactional 注解无效,发生异常不回滚

  • 请确认该 Bean 得到正确配置,并且@TransactionalrollbackFor 配置正确
    @Bean
public PlatformTransactionManager transactionManager() {
return new DataSourceTransactionManager(dynamicDataSource());
}

5. 通过 AOP 判断 DAO 层方法名时切换数据源无效

当切面指向了 DAO 层后无论如何设置切面的顺序,都无法在执行查询之前切换数据源,但是切面改为 Service 层后可以正常工作

  • 解决方法: 请确认 @Transactional 注解是加在方法上而不是 Service 类上,添加了 @Transactional 的方法因为在 Service 层开启了事务,
    会在事务结束之后才会切换数据源

  • 检出 DataSourceTransactionManager Bean 注入正确

    @Bean 
public PlatformTransactionManager transactionManager() {
return new DataSourceTransactionManager(dynamicDataSource());
}

6. The dependencies of some of the beans in the application context form a cycle

  • 错误信息:
The dependencies of some of the beans in the application context form a cycle:

produceController (field private cn.com.hellowood.dynamicdatasource.service.ProductService cn.com.hellowood.dynamicdatasource.controller.ProduceController.productService)

productService (field private cn.com.hellowood.dynamicdatasource.mapper.ProductDao cn.com.hellowood.dynamicdatasource.service.ProductService.productDao)

productDao defined in file [/Users/he*/Downloads/Dev/SpringBoot/DynamicDataSource/out/production/classes/cn/com/hellowood/dynamicdatasource/mapper/ProductDao.class]

sqlSessionFactoryBean defined in class path resource [cn/com/hellowood/dynamicdatasource/configuration/DataSourceConfigurer.class]
┌─────┐
| dynamicDataSource defined in class path resource [cn/com/hellowood/dynamicdatasource/configuration/DataSourceConfigurer.class]
↑ ↓
| master defined in class path resource [cn/com/hellowood/dynamicdatasource/configuration/DataSourceConfigurer.class]
↑ ↓
| dataSourceInitializer
└─────┘

这是因为在注入 DataSource 的实例的时候产生了循环调用,第一个注入的 Bean 依赖于其他的 Bean, 而被依赖的 Bean 产生依赖传递,依赖第一个
注入的 Bean, 陷入了循环,无法启动项目

  • 解决方法:将 @Primary 注解指向没有依赖的 Bean,如:

/**
* master DataSource
* @Primary 注解用于标识默认使用的 DataSource Bean,因为有三个 DataSource Bean,该注解可用于 master
* 或 slave DataSource Bean, 但不能用于 dynamicDataSource Bean, 否则会产生循环调用
*
* @ConfigurationProperties 注解用于从 application.properties 文件中读取配置,为 Bean 设置属性
* @return data source
*/

@Bean("master")
@Primary
@ConfigurationProperties(prefix = "application.server.db.master")
public DataSource master() {
return DataSourceBuilder.create().build();
}

@Bean("slave")
@ConfigurationProperties(prefix = "application.server.db.slave")
public DataSource slave() {
return DataSourceBuilder.create().build();
}

@Bean("dynamicDataSource")
public DataSource dynamicDataSource() {
DynamicRoutingDataSource dynamicRoutingDataSource = new DynamicRoutingDataSource();
Map<Object, Object> dataSourceMap = new HashMap<>(2);
dataSourceMap.put("master", master());
dataSourceMap.put("slave", slave());

// Set master datasource as default
dynamicRoutingDataSource.setDefaultTargetDataSource(master());
// Set master and slave datasource as target datasource
dynamicRoutingDataSource.setTargetDataSources(dataSourceMap);

// To put datasource keys into DataSourceContextHolder to judge if the datasource is exist
DynamicDataSourceContextHolder.dataSourceKeys.addAll(dataSourceMap.keySet());
return dynamicRoutingDataSource;
}