多数据源配置下如何指定使用次级数据库的EntityManagerFactory

配置多数据源后，尝试使用次级数据库的EntityManagerFactory时，系统总是自动引用主数据库的配置，导致报错“Not an Entity”。以下是相关配置信息：

application.properties #

spring.ds.datasource1.url=jdbc:postgresql:x
spring.ds.datasource1.username=user
spring.ds.datasource1.password=

spring.ds.datasource2.url=jdbc:postgresql:x
spring.ds.datasource2.username=user
spring.ds.datasource2.password=

Datasource 1 配置 #

@EnableJpaRepositories(basePackages = "eu.example", entityManagerFactoryRef = "ds1EntityManagerFactory", transactionManagerRef = "ds1TransactionManager")
@Configuration
public class Ds1DataSourceConfiguration {

    private static final String DS1_ENTITY_MANAGER_FACTORY = "ds1EntityManagerFactory";
    private static final String DS1_TRANSACTION_MANAGER = "ds1TransactionManager";

    @Primary
    @Bean
    @ConfigurationProperties(prefix = "spring.ds.datasource1")
    public DataSourceProperties ds1DataSourceProperties() {
        return new DataSourceProperties();
    }

    @Primary
    @Bean
    @ConfigurationProperties("spring.ds.datasource1")
    public DataSource ds1DataSource(DataSourceProperties properties) {
        return properties
                .initializeDataSourceBuilder()
                .build();
    }

    @Primary
    @Bean(name = DS1_ENTITY_MANAGER_FACTORY)
    public LocalContainerEntityManagerFactoryBean ds1EntityManagerFactoryBean(
            EntityManagerFactoryBuilder factoryBuilder, DataSource ds1Ds) {
        return factoryBuilder
                .dataSource(ds1Ds)
                .packages("eu.example.domain.entity.ds1")
                .build();
    }

    @Primary
    @Bean(name = DS1_TRANSACTION_MANAGER)
    public PlatformTransactionManager ds1TransactionManager(
            @Qualifier(DS1_ENTITY_MANAGER_FACTORY) LocalContainerEntityManagerFactoryBean managerFactoryBean) {
        JpaTransactionManager jpaTransactionManager = new JpaTransactionManager();
        jpaTransactionManager.setEntityManagerFactory(managerFactoryBean.getObject());
        return jpaTransactionManager;
    }

}

Datasource 2 配置 #

与上述Ds1配置结构一致，但未添加@Primary注解。

当前Service类 #

@Service
public class TestService{

    private final EntityManagerFactory et2;
    
    // 业务方法...

}

解决方案 #

要正确注入次级数据库的EntityManagerFactory，只需两步：

• 确认次级数据源EntityManagerFactory的Bean名称
  在Ds2的配置类中，确保EntityManagerFactory的Bean有明确的唯一名称，同时指定对应实体类的包路径：

  // Ds2配置类中的EntityManagerFactory Bean定义
  @Bean(name = "ds2EntityManagerFactory")
  public LocalContainerEntityManagerFactoryBean ds2EntityManagerFactoryBean(
          EntityManagerFactoryBuilder factoryBuilder, DataSource ds2Ds) {
      return factoryBuilder
              .dataSource(ds2Ds)
              .packages("eu.example.domain.entity.ds2")
              .build();
  }
  

  这里的name属性值ds2EntityManagerFactory是核心标识，需保证与Ds1的Bean名称不重复。

• 在Service中通过@Qualifier指定要注入的Bean
  由于Spring容器中存在两个EntityManagerFactory类型的Bean，且Ds1的Bean带有@Primary注解，默认会优先注入主库实例。必须通过@Qualifier注解明确指定次级库的Bean名称：

  @Service
  public class TestService{
  
      private final EntityManagerFactory et2;
      
      // 构造方法注入（推荐方式）
      public TestService(@Qualifier("ds2EntityManagerFactory") EntityManagerFactory et2) {
          this.et2 = et2;
      }
  }
  

这样就能确保注入的是次级数据库对应的EntityManagerFactory，避免因默认选择主库而导致的“Not an Entity”错误。

内容的提问来源于stack exchange，提问作者Minez97