springboot2+mybatis多种方式实现多数据配置方法

业务系统复杂程度增加，为了解决数据库I/O瓶颈，很自然会进行拆库拆表分服务来应对。这就会出现一个系统中可能会访问多处数据库，需要配置多个数据源。

第一种场景：项目服务从其它多处数据库取基础数据进行业务处理，因此各库之间不会出现重表等情况。

第二种场景：为了减轻写入压力进行读写分库，读走从库，写为主库。此种表名等信息皆为一致。

第三种场景：以上两种皆有。对于某些业务需要大数据量的汇总统计，希望不影响正常业务必须走从库（表信息一致），某些配置信息不存在读写压力，出现不分库（表信息不一致）

项目源代码：

https://github.com/zzsong/springboot-multiple-datasource.git

有三个目录：

one:
直接使用多@Bean配置，@MapperScan来路径区分读何库

two:
使用注解的方式来标识走何dataSource,AOP拦截注入动态数据源

third:
使用spring的Bean命名策略进行区分数据来源

项目技术选型： springBoot2.2.5 + mybatis + druid + mysql

先看主要的pom包

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.2.5.RELEASE</version>
    <relativePath/> 
  </parent>

        <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-data-jdbc</artifactId>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-data-jdbc</artifactId>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-aop</artifactId>
    </dependency>
    <dependency>
      <groupId>org.mybatis.spring.boot</groupId>
      <artifactId>mybatis-spring-boot-starter</artifactId>
      <version>2.1.2</version>
    </dependency>

    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>8.0.19</version>
    </dependency>
    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>druid-spring-boot-starter</artifactId>
      <version>1.1.21</version>
    </dependency>

application.yml

spring:
 datasource:
  druid:
   core:
    url: jdbc:mysql:///kc_core?characterEncoding=utf-8&serverTimezone=Asia/Shanghai
    username: root
    password: 123456
    driver-class-name: com.mysql.cj.jdbc.Driver
    type: com.alibaba.druid.pool.DruidDataSource
   schedule:
    url: jdbc:mysql:///kc_schedule?characterEncoding=utf-8&serverTimezone=Asia/Shanghai
    username: root
    password: 123456
    driver-class-name: com.mysql.cj.jdbc.Driver
    type: com.alibaba.druid.pool.DruidDataSource

mysql新版本必须带有serverTimezone，不然会报连接异常。

第一种：通过@MapperScans 扫描匹配相关的数据源

@Configuration
@MapperScans({
    @MapperScan(basePackages = "com.zss.one.mapper.core", sqlSessionTemplateRef = "coreSqlSessionTemplate",sqlSessionFactoryRef = "coreSqlSessionFactory"),
    @MapperScan(basePackages = "com.zss.one.mapper.schedule", sqlSessionTemplateRef = "scheduleSqlSessionTemplate",sqlSessionFactoryRef = "scheduleSqlSessionFactory")
})
public class MybatisOneConfig {

  @Bean
  @ConfigurationProperties(prefix = "spring.datasource.druid.core")
  public DataSource coreDataSource(){
    return DruidDataSourceBuilder.create().build();
  }

  @Bean
  public SqlSessionFactory coreSqlSessionFactory(@Qualifier("coreDataSource") DataSource coreDataSource) throws Exception {
    SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
    sessionFactory.setDataSource(coreDataSource);
    sessionFactory.getObject().getConfiguration().setJdbcTypeForNull(null);
    sessionFactory.getObject().getConfiguration().setMapUnderscoreToCamelCase(true);
    return sessionFactory.getObject();
  }

  @Bean
  public SqlSessionTemplate coreSqlSessionTemplate(@Qualifier("coreSqlSessionFactory") SqlSessionFactory sqlSessionFactory) throws Exception {
    return new SqlSessionTemplate(sqlSessionFactory);
  }

  //======schedule========
  @Bean
  @ConfigurationProperties(prefix = "spring.datasource.druid.schedule")
  public DataSource scheduleDataSource(){
    return DruidDataSourceBuilder.create().build();
  }

  @Bean
  public SqlSessionFactory scheduleSqlSessionFactory(@Qualifier("scheduleDataSource") DataSource coreDataSource) throws Exception {
    SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
    sessionFactory.setDataSource(coreDataSource);
    sessionFactory.getObject().getConfiguration().setJdbcTypeForNull(null);
    sessionFactory.getObject().getConfiguration().setMapUnderscoreToCamelCase(true);
    return sessionFactory.getObject();
  }

  @Bean
  public SqlSessionTemplate scheduleSqlSessionTemplate(@Qualifier("scheduleSqlSessionFactory") SqlSessionFactory sqlSessionFactory) throws Exception {
    return new SqlSessionTemplate(sqlSessionFactory);
  }
}

第二种是动态数据源模式，通过AOP切入注解引导使用何数据源。用自定义注解@interface来标识方法走对应的数据源。

注意事项：类中的方法再调用带数据源的方法，不能被AOP切入

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface TargetDataSource {
  String value();
}

extends spring的动态DataSource路由来匹配

public class DynamicDataSource extends AbstractRoutingDataSource {

  @Override
  protected Object determineCurrentLookupKey() {
    return DataSourceContextRouting.getDataSourceName();
  }
}

@Configuration
//@EnableConfigurationProperties(MybatisProperties.class)//不要使用此公共配置，Configuration会破坏相关dataSource的配置
@MapperScan("com.zss.two.mapper")
public class MybatisConfig {

  @Bean
  @ConfigurationProperties(prefix = "spring.datasource.druid.core")
  public DataSource coreDataSource() {
    return DruidDataSourceBuilder.create().build();
  }

  @Bean
  @ConfigurationProperties(prefix = "spring.datasource.druid.schedule")
  public DataSource scheduleDataSource() {
    return DruidDataSourceBuilder.create().build();
  }

  @Autowired
  @Qualifier("coreDataSource")
  private DataSource coreDataSource;

  @Autowired
  @Qualifier("scheduleDataSource")
  private DataSource scheduleDataSource;

  @Bean
  public DynamicDataSource dataSource() {
    Map<Object, Object> targetDataSources = new HashMap<>();
    targetDataSources.put(DataSourceConstants.CORE_DATA_SOURCE, coreDataSource);
    targetDataSources.put(DataSourceConstants.SCHEDULE_DATA_SOURCE, scheduleDataSource);

    DynamicDataSource dataSource = new DynamicDataSource();

    //设置数据源映射
    dataSource.setTargetDataSources(targetDataSources);
////    设置默认数据源，当无法映射到数据源时会使用默认数据源
    dataSource.setDefaultTargetDataSource(coreDataSource);
    dataSource.afterPropertiesSet();
    return dataSource;
  }
  /**
   * 根据数据源创建SqlSessionFactory
   */
  @Bean
  public SqlSessionFactory sqlSessionFactory(DynamicDataSource dataSource) throws Exception {
    SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
    sessionFactory.setDataSource(dataSource);
    sessionFactory.getObject().getConfiguration().setJdbcTypeForNull(null);
    sessionFactory.getObject().getConfiguration().setMapUnderscoreToCamelCase(true);
    return sessionFactory.getObject();
  }

  @Bean
  public SqlSessionTemplate sqlSessionTemplate(SqlSessionFactory sqlSessionFactory) throws Exception {
    return new SqlSessionTemplate(sqlSessionFactory);
  }

第三种，自定义Bean命名策略，按beanName进行自动匹配使用数据源

@Component
public class CoreBeanNameGenerator implements BeanNameGenerator {
  @Override
  public String generateBeanName(BeanDefinition definition, BeanDefinitionRegistry registry) {
    return "core"+ ClassUtils.getShortName(definition.getBeanClassName());
  }
}

@Component
public class ScheduleBeanNameGenerator implements BeanNameGenerator {
  @Override
  public String generateBeanName(BeanDefinition definition, BeanDefinitionRegistry registry) {
    return "schedule"+ ClassUtils.getShortName(definition.getBeanClassName());
  }
}

使用mybatis MapperScannerConfigurer自动扫描，将Mapper接口生成注入到spring

  @Bean
  public MapperScannerConfigurer coreMapperScannerConfig(CoreBeanNameGenerator coreBeanNameGenerator){
    MapperScannerConfigurer configurer = new MapperScannerConfigurer();
    configurer.setNameGenerator(coreBeanNameGenerator);
    configurer.setBasePackage("com.zss.third.mapper.core,com.zss.third.mapper.order");
    configurer.setSqlSessionFactoryBeanName("coreSqlSessionFactory");
    configurer.setSqlSessionTemplateBeanName("coreSqlSessionTemplate");
    return configurer;
  }

  @Bean
  public MapperScannerConfigurer scheduleMapperScannerConfig(ScheduleBeanNameGenerator scheduleBeanNameGenerator){
    MapperScannerConfigurer configurer = new MapperScannerConfigurer();
    configurer.setNameGenerator(scheduleBeanNameGenerator);
    configurer.setBasePackage("com.zss.third.mapper.schedule,com.zss.third.mapper.order");
    configurer.setSqlSessionFactoryBeanName("scheduleSqlSessionFactory");
    configurer.setSqlSessionTemplateBeanName("scheduleSqlSessionTemplate");
    return configurer;
  }

到此，三种多数据源匹配主要点介绍完，详细直接下载github项目。在resources/db含有相关测试表及数据脚本。

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