Spring Boot アプリケーションで複数のデータソースを使用するように Spring Data JPA を構成するにはどうすればよいですか?

<code class="java">@Configuration
@EnableJpaRepositories(
        entityManagerFactoryRef = "customerEntityManager",
        transactionManagerRef = "customerTransactionManager",
        basePackages = {"com.mm.repository.customer"})
public class CustomerDataSourceConfiguration {

    @Bean(name = "customerDataSource")
    public DataSource dataSource() {
        return DataSourceBuilder.create()
                .url("jdbc:h2:mem:customer:H2")
                .driverClassName("org.h2.Driver")
                .username("sa")
                .password("")
                .build();
    }

    @Bean(name = "customerEntityManager")
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
        LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
        em.setDataSource(dataSource());
        em.setPackagesToScan(new String[] {"com.mm.domain.customer"});

        JpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        em.setJpaVendorAdapter(vendorAdapter);
        em.setJpaProperties(additionalJpaProperties());
        em.setPersistenceUnitName("customerPersistence");
        em.setPackagesToScan("com.mm.domain.customer");

        return em;
    }

    Properties additionalJpaProperties() {
        Properties properties = new Properties();
        properties.setProperty("hibernate.hbm2ddl.auto", "create-drop");
        properties.setProperty("hibernate.dialect", "org.hibernate.dialect.H2Dialect");
        properties.setProperty("hibernate.show_sql", "true");

        return properties;
    }

    @Bean(name = "customerTransactionManager")
    public PlatformTransactionManager transactionManager(EntityManagerFactory emf) {
        JpaTransactionManager transactionManager = new JpaTransactionManager();
        transactionManager.setEntityManagerFactory(emf);

        return transactionManager;
    }
}</code>

<code class="java">@Configuration
@EnableJpaRepositories(
        entityManagerFactoryRef = "genericEntityManager",
        transactionManagerRef = "genericTransactionManager",
        basePackages = {"com.mm.repository.generic"})
public class GenericDataSourceConfiguration {

    @Bean(name = "genericDataSource")
    public DataSource dataSource() {
        return DataSourceBuilder.create()
                .url("jdbc:h2:mem:generic:H2")
                .driverClassName("org.h2.Driver")
                .username("sa")
                .password("")
                .build();
    }

    @Bean(name = "genericEntityManager")
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
        LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
        em.setDataSource(dataSource());
        em.setPackagesToScan(new String[] {"com.mm.domain.generic"});

        JpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        em.setJpaVendorAdapter(vendorAdapter);
        em.setJpaProperties(additionalJpaProperties());
        em.setPersistenceUnitName("genericPersistence");
        em.setPackagesToScan("com.mm.domain.generic");

        return em;
    }

    Properties additionalJpaProperties() {
        Properties properties = new Properties();
        properties.setProperty("hibernate.hbm2ddl.auto", "create-drop");
        properties.setProperty("hibernate.dialect", "org.hibernate.dialect.H2Dialect");
        properties.setProperty("hibernate.show_sql", "true");

        return properties;
    }

    @Bean(name = "genericTransactionManager")
    public PlatformTransactionManager transactionManager(EntityManagerFactory emf) {
        JpaTransactionManager transactionManager = new JpaTransactionManager();
        transactionManager.setEntityManagerFactory(emf);

        return transactionManager;
    }
}</code>

<code class="java">@Configuration
@ComponentScan
@EnableAutoConfiguration
public class Application extends SpringApplication {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Bean
    public ServletRegistrationBean h2Console() {
        ServletRegistrationBean reg = new ServletRegistrationBean(new WebServlet(), "/console/*");
        reg.setLoadOnStartup(1);
        return reg;
    }
}</code>

<code class="java">@Entity
@Table(name = "customer")
@Data
@EqualsAndHashCode(exclude = {"id"})
public class Customer {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;

    @Column(name = "name", nullable = false)
    private String name;

    @Column(name = "age", nullable = false)
    private Integer age;

    ....
}</code>

<code class="java">@Entity
@Table(name = "order")
@Data
@EqualsAndHashCode(exclude = {"id"})
public class Order {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;

    @Column(name = "code", nullable = false)
    private Integer code;

    @Column(name = "quality", nullable = false)
    private Integer quality;
}</code>

<code class="java">public interface CustomerRepository extends JpaRepository<Customer, Integer> {}</code>

<code class="java">public interface GenericRepository extends JpaRepository<Generic, Integer> {}</code>