在 Spring Boot 中使用 EntityManager

Question

我想在SpringBoot 中使用EntityManager。

应用程序

@Configuration
@EnableRetry // To enable Spring retry
@EnableJpaRepositories
@EnableAspectJAutoProxy(proxyTargetClass=true)
@SpringBootApplication
public class Application {

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

    @Bean
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }    
}

邮件配置

@Configuration
@EnableJpaRepositories(
        entityManagerFactoryRef = "mailEntityManager",
        transactionManagerRef = "mailTransactionManager",
        basePackageClasses = MmcMonitoringLog.class)

public class MailConfig {

    @Autowired(required = false)
    private PersistenceUnitManager persistenceUnitManager;

    @Bean
    @ConfigurationProperties("app.order.jpa")
    public JpaProperties orderJpaProperties() {
        return new JpaProperties();
    }

    @Bean
    @ConfigurationProperties(prefix = "app.order.datasource")
    public DataSource orderDataSource() {
        return (DataSource) DataSourceBuilder.create().type(DataSource.class).build();
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean orderEntityManager(
            JpaProperties orderJpaProperties) {
        EntityManagerFactoryBuilder builder = createEntityManagerFactoryBuilder(orderJpaProperties);
        return builder
                .dataSource(orderDataSource())
                .packages(MmcMonitoringLog.class)
                .persistenceUnit("ordersDs")
                .build();
    }

    @Bean
    public JpaTransactionManager orderTransactionManager(EntityManagerFactory orderEntityManager) {
        return new JpaTransactionManager(orderEntityManager);
    }

    private EntityManagerFactoryBuilder createEntityManagerFactoryBuilder(JpaProperties customerJpaProperties) {
        JpaVendorAdapter jpaVendorAdapter = createJpaVendorAdapter(customerJpaProperties);
        return new EntityManagerFactoryBuilder(jpaVendorAdapter,
                customerJpaProperties.getProperties(), this.persistenceUnitManager);
    }

    private JpaVendorAdapter createJpaVendorAdapter(JpaProperties jpaProperties) {
        AbstractJpaVendorAdapter adapter = new HibernateJpaVendorAdapter();
        adapter.setShowSql(jpaProperties.isShowSql());
        adapter.setDatabase(jpaProperties.getDatabase());
        adapter.setDatabasePlatform(jpaProperties.getDatabasePlatform());
        adapter.setGenerateDdl(jpaProperties.isGenerateDdl());
        return adapter;
    }

}

邮件服务

public class MailService extends TaskAdaptor implements Runnable {

    @Autowired
    MmcMonitoringLogRepository mmcMonitoringLogRepository;

    @Override
    public void run() {

   List<MmcMonitoringLog> list = mmcMonitoringLogRepository.findByMonitoringLog("1");
   ......
}

appication.properties

spring.datasource.url= jdbc:mysql://xxxx:3306/adb?autoReconnect=true&useSSL=false
spring.datasource.username=xxx
spring.datasource.password=xxx


# The SQL dialect makes Hibernate generate better SQL for the chosen database
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5Dialect

# Hibernate ddl auto (create, create-drop, update)
spring.jpa.hibernate.ddl-auto = none

我尝试实现以下https://github.com/snicoll-demos/demo-multi-entity-managers/blob/master/src/main/java/demo/order/OrderConfig.java，但我的 SpringBoot 立即停止，没有抛出任何异常。如果我删除 MailConfig，Springboot 可以启动。有什么问题 ？我走对了吗？

Answer 1

我认为你没有设置数据源的值。您需要在 application.properties 中设置“app.order.jpa”和“app.order.datasource”属性以使示例正常运行。

关于配置属性你可以在这里阅读：

http://www.baeldung.com/configuration-properties-in-spring-boot

请看这里的例子：

https://github.com/snicoll-demos/demo-multi-entity-managers/blob/master/src/main/resources/application.properties

app.customer.datasource.url=jdbc:h2:mem:customers;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=FALSE
app.customer.datasource.driver-class-name=org.h2.Driver
app.customer.jpa.properties.hibernate.hbm2ddl.auto=create

app.order.datasource.url=jdbc:h2:mem:orders;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=FALSE
app.order.datasource.driver-class-name=org.h2.Driver
app.order.jpa.properties.hibernate.hbm2ddl.auto=create

Answer 2

spring boot 中不需要 bean 配置，它在内部管理这种类型的配置。 您可以使用 JPA 的 EntityManagerFactory 类，如

@Autowired
 EntityManagerFactory emf;

Answer 3

正如 Mukesh Dharajiya 的回答所提供的：

@Autowired EntityManagerFactory factory;

private manageEntities(){

    // javadoc: Create a new application-managed EntityManager. 
    // This method returns a new EntityManager instance each time it is invoked. 
    EntityManager em = emFactory.createEntityManager();

}

编辑：实际上你使用LocalContainerEntityManagerFactoryBean，我刚刚注意到，所以下面的信息可能不适用..

在您的解决方案中，您尝试创建一个 bean 来覆盖 springboot 已经自动配置的 entityManagerFactory。

我对此不是 100% 确定，但我相信您需要这样做：

1. 排除自动配置（@EnableJpaRepositories 在配置 jpa 之前可能无法工作）：

@SpringBootApplication(exclude = {
        DataSourceAutoConfiguration.class,
        DataSourceTransactionManagerAutoConfiguration.class,
        HibernateJpaAutoConfiguration.class})
public class Application {
    public static void main(String[] args) {
        // Now spring will not autoconfigure jpa for you, so there should not already be a factory bean
        // If you do this you will need to implement all of the steps missed in the autoconfig to get jpa functioning again
        SpringApplication.run(Application.class, args);
    }
}

1. （也许？- 未测试）设置 spring.main.allow-bean-definition-overriding=true 或命名 bean，并在属性中使用 @Qualified 自动装配它，以便您可以覆盖现有的工厂 bean。