Spring Data JPA来进行跨数据库关联查询例子
时间: 2024-02-19 22:04:02 浏览: 223
下面是一个简单的使用Spring Data JPA进行跨数据库关联查询的示例:
假设我们有两个数据库,一个是用户数据库,另一个是订单数据库,它们都有一个共同的字段userId。现在我们想要关联查询用户和他们的订单信息,并且这些信息存储在不同的数据库中。
首先,我们需要在Spring Boot应用程序中配置两个数据源,并分别创建两个JPA Repositories:
```java
@Configuration
@EnableJpaRepositories(basePackages = "com.example.user.repository", entityManagerFactoryRef = "userEntityManagerFactory", transactionManagerRef = "userTransactionManager")
public class UserDataSourceConfig {
@Primary
@Bean(name = "userDataSource")
@ConfigurationProperties(prefix = "spring.datasource.user")
public DataSource userDataSource() {
return DataSourceBuilder.create().build();
}
@Primary
@Bean(name = "userEntityManagerFactory")
public LocalContainerEntityManagerFactoryBean userEntityManagerFactory(EntityManagerFactoryBuilder builder, @Qualifier("userDataSource") DataSource dataSource) {
return builder.dataSource(dataSource).packages("com.example.user.entity").persistenceUnit("user").build();
}
@Primary
@Bean(name = "userTransactionManager")
public PlatformTransactionManager userTransactionManager(@Qualifier("userEntityManagerFactory") EntityManagerFactory entityManagerFactory) {
return new JpaTransactionManager(entityManagerFactory);
}
}
@Configuration
@EnableJpaRepositories(basePackages = "com.example.order.repository", entityManagerFactoryRef = "orderEntityManagerFactory", transactionManagerRef = "orderTransactionManager")
public class OrderDataSourceConfig {
@Bean(name = "orderDataSource")
@ConfigurationProperties(prefix = "spring.datasource.order")
public DataSource orderDataSource() {
return DataSourceBuilder.create().build();
}
@Bean(name = "orderEntityManagerFactory")
public LocalContainerEntityManagerFactoryBean orderEntityManagerFactory(EntityManagerFactoryBuilder builder, @Qualifier("orderDataSource") DataSource dataSource) {
return builder.dataSource(dataSource).packages("com.example.order.entity").persistenceUnit("order").build();
}
@Bean(name = "orderTransactionManager")
public PlatformTransactionManager orderTransactionManager(@Qualifier("orderEntityManagerFactory") EntityManagerFactory entityManagerFactory) {
return new JpaTransactionManager(entityManagerFactory);
}
}
@Repository
public interface UserRepository extends JpaRepository<User, Long> {
}
@Repository
public interface OrderRepository extends JpaRepository<Order, Long> {
}
```
然后,我们可以使用Spring Data JPA的@Query注解来编写关联查询的语句。例如,我们可以在OrderRepository中编写以下查询:
```java
@Repository
public interface OrderRepository extends JpaRepository<Order, Long> {
@Query(value = "SELECT o.* FROM order_db.order o JOIN user_db.user u ON o.user_id = u.id WHERE u.name = ?1", nativeQuery = true)
List<Order> findOrdersByUserName(String userName);
}
```
在这个查询中,我们使用了原生SQL语句,来跨数据库关联查询用户和订单信息。
最后,我们可以在Controller中调用这个查询方法,并返回结果给客户端:
```java
@RestController
@RequestMapping("/orders")
public class OrderController {
@Autowired
private OrderRepository orderRepository;
@GetMapping("/by-user-name")
public List<Order> getOrdersByUserName(@RequestParam String userName) {
return orderRepository.findOrdersByUserName(userName);
}
}
```
这样,我们就完成了使用Spring Data JPA进行跨数据库关联查询的示例。
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