如何在春季使用第二个数据源?

Question

>我在这里下载了示例代码

https://github.com/spring-projects/spring-data-examples/tree/master/jpa/multiple-datasources

但我仍然不明白存储库如何连接到数据源。即使我查看配置类，它也没有引用存储库。在存储库界面中，它不引用数据源或配置。

因此，当您使用两个不同的存储库进行保存时，它如何知道每个存储库要转到哪个数据源？

Answer 1

在您链接的示例存储库中，每个配置类都使用@EnableJpaRepositories进行注释，该仅在注释类和子包的包中扫描存储库 - 这是数据源和存储库之间关系发生的地方。

Answer 2

注意配置(注释为/* 重要 */)

在订单配置中

@Configuration
/* important */
@EnableJpaRepositories(entityManagerFactoryRef = "orderEntityManagerFactory",
transactionManagerRef = "orderTransactionManager")
class OrderConfig {
@Bean
PlatformTransactionManager orderTransactionManager() {
return new JpaTransactionManager(orderEntityManagerFactory().getObject());
}
@Bean
LocalContainerEntityManagerFactoryBean orderEntityManagerFactory() {
HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
vendorAdapter.setGenerateDdl(true);
LocalContainerEntityManagerFactoryBean factoryBean = new LocalContainerEntityManagerFactoryBean();
/* important */
factoryBean.setDataSource(orderDataSource());
factoryBean.setJpaVendorAdapter(vendorAdapter);
factoryBean.setPackagesToScan(OrderConfig.class.getPackage().getName());
return factoryBean;
}
@Bean
DataSource orderDataSource() {
return new EmbeddedDatabaseBuilder().//
setType(EmbeddedDatabaseType.HSQL).//
setName("orders").//
build();
}
}

和， 客户配置

@Configuration
/* important */
@EnableJpaRepositories(entityManagerFactoryRef = "customerEntityManagerFactory",
transactionManagerRef = "customerTransactionManager")
class CustomerConfig {
@Bean
PlatformTransactionManager customerTransactionManager() {
return new JpaTransactionManager(customerEntityManagerFactory().getObject());
}
@Bean
LocalContainerEntityManagerFactoryBean customerEntityManagerFactory() {
HibernateJpaVendorAdapter jpaVendorAdapter = new HibernateJpaVendorAdapter();
jpaVendorAdapter.setGenerateDdl(true);
LocalContainerEntityManagerFactoryBean factoryBean = new LocalContainerEntityManagerFactoryBean();
/* important */
factoryBean.setDataSource(customerDataSource());
factoryBean.setJpaVendorAdapter(jpaVendorAdapter);
factoryBean.setPackagesToScan(CustomerConfig.class.getPackage().getName());
return factoryBean;
}
@Bean
DataSource customerDataSource() {
return new EmbeddedDatabaseBuilder().//
setType(EmbeddedDatabaseType.HSQL).//
setName("customers").//
build();
}
}

最后是数据初始值设定项中的@Transactional注释

/* important */
@Transactional("customerTransactionManager")
public CustomerId initializeCustomer() {
return customers.save(new Customer("Dave", "Matthews")).getId();
}

使用在CustomerConfig中配置的customerTransactionManager

和

/* important */
@Transactional("orderTransactionManager")
public Order initializeOrder(CustomerId customer) {
Assert.notNull(customer, "Customer identifier must not be null!");
Order order = new Order(customer);
order.add(new LineItem("Lakewood Guitar"));
return orders.save(order);
}

使用在OrderConfig中配置的orderTransactionManager

基本上，您正在配置不同的datasources，不同的entityManagers，不同的transactionManagers，并根据您的选择专门引用它们。