# 79.8 使用两个EntityManagers

即使默认的`EntityManagerFactory`工作的很好，你也需要定义一个新的`EntityManagerFactory`，因为一旦出现第二个该类型的bean，默认的将会被关闭。为了轻松的实现该操作，你可以使用Spring Boot提供的`EntityManagerBuilder`，或者如果你喜欢的话可以直接使用来自Spring ORM的`LocalContainerEntityManagerFactoryBean`。

示例：

```java
// add two data sources configured as above

@Bean
public LocalContainerEntityManagerFactoryBean customerEntityManagerFactory(
        EntityManagerFactoryBuilder builder) {
    return builder
            .dataSource(customerDataSource())
            .packages(Customer.class)
            .persistenceUnit("customers")
            .build();
}

@Bean
public LocalContainerEntityManagerFactoryBean orderEntityManagerFactory(
        EntityManagerFactoryBuilder builder) {
    return builder
            .dataSource(orderDataSource())
            .packages(Order.class)
            .persistenceUnit("orders")
            .build();
}
```

上面的配置靠自己基本可以运行，想要完成作品你还需要为两个`EntityManagers`配置`TransactionManagers`。其中的一个会被Spring Boot默认的`JpaTransactionManager`获取，如果你将它标记为`@Primary`。另一个需要显式注入到一个新实例。或你可以使用一个JTA事物管理器生成它两个。

如果使用Spring Data，你需要相应地需要配置`@EnableJpaRepositories`：

```java
@Configuration
@EnableJpaRepositories(basePackageClasses = Customer.class,
        entityManagerFactoryRef = "customerEntityManagerFactory")
public class CustomerConfiguration {
    ...
}

@Configuration
@EnableJpaRepositories(basePackageClasses = Order.class,
        entityManagerFactoryRef = "orderEntityManagerFactory")
public class OrderConfiguration {
    ...
}
```


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