使用Spring时如何注入多个JPA EntityManager（持久性单元）

  • Z时代
  • 2024-01-10
  • 分类：问答

我需要使用一个数据库进行查询（非修改），而使用一个数据库进行命令（修改）。我正在使用Spring Data JPA，所以我有两个配置类：

@Configuration
@EnableJpaRepositories(value = "com.company.read",
        entityManagerFactoryRef = "readingEntityManagerFactory",
        transactionManagerRef = "readingTransactionManager")
@EnableTransactionManagement
public class SpringDataJpaReadingConfiguration {
    @Bean(name = "readingEntityManagerFactory")
    public EntityManagerFactory readingEntityManagerFactory() {
        return Persistence.createEntityManagerFactory("persistence.reading");
    }
    @Bean(name = "readingExceptionTranslator")
    public HibernateExceptionTranslator readingHibernateExceptionTranslator() {
        return new HibernateExceptionTranslator();
    }
    @Bean(name = "readingTransactionManager")
    public JpaTransactionManager readingTransactionManager() {
        return new JpaTransactionManager();
    }
}
@Configuration
@EnableJpaRepositories(value = "com.company.write",
        entityManagerFactoryRef = "writingEntityManagerFactory",
        transactionManagerRef = "writingTransactionManager")
@EnableTransactionManagement
public class SpringDataJpaWritingConfiguration {
    @Bean(name = "writingEntityManagerFactory")
    public EntityManagerFactory writingEntityManagerFactory() {
        return Persistence.createEntityManagerFactory("persistence.writing");
    }
    @Bean(name = "writingExceptionTranslator")
    public HibernateExceptionTranslator writingHibernateExceptionTranslator() {
        return new HibernateExceptionTranslator();
    }
    @Bean(name = "writingTransactionManager")
    public JpaTransactionManager writingTransactionManager() {
        return new JpaTransactionManager();
    }
}

在我的存储库中，有时我需要决定与EntityManager一起使用，如下所示：

@Repository
public class UserReadingRepository {
    @PersistenceContext(unitName = "persistence.reading")
    private EntityManager em;
    // some useful queries here
}

我使用在我的定义持久性单元的名称 ：

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
             version="2.0">
    <persistence-unit name="persistence.reading" transaction-type="RESOURCE_LOCAL">
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
        <non-jta-data-source>ReadingDS</non-jta-data-source>
        <properties>
            <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect" />
            <property name="hibernate.show_sql" value="true" />
        </properties>
    </persistence-unit>
    <persistence-unit name="persistence.writing" transaction-type="RESOURCE_LOCAL">
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
        <non-jta-data-source>WritingDS</non-jta-data-source>
        <properties>
            <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect" />
            <property name="hibernate.show_sql" value="true" />
        </properties>
    </persistence-unit>
</persistence>

org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean

named 'persistence.reading'定义了弹簧抛出。奇怪的是，看起来Spring尝试使用持久性单元名称实例化 bean

？我配置错误了吗？

：当我unitName =

"persistence.reading"从@PersistenceContext批注中删除时，我将得到以下错误：

org.springframework.beans.factory.NoUniqueBeanDefinitionException: No

qualifying bean of type [javax.persistence.EntityManagerFactory] is defined:

expected single matching bean but found 2:

readingEntityManagerFactory,writingEntityManagerFactory

：Rohit建议（在评论中）连接EntityManagerFactory。因此，我尝试执行以下操作：

@PersistenceUnit(unitName = "persistence.reading")
private EntityManagerFactory emf;

但Spring仅报告： org.springframework.beans.factory.NoSuchBeanDefinitionException:

No bean named 'persistence.reading' is defined

：感谢Vlad的回答，我能够更新代码以使用以下代码（只需确保还定义了dataSourcebean）：

@Bean(name = "readingEntityManagerFactory")
public EntityManagerFactory readingEntityManagerFactory() {
    LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
    em.setPersistenceUnitName("persistence.reading");
    em.setDataSource(dataSource());
    em.setPackagesToScan("com.company");
    em.setJpaVendorAdapter(new HibernateJpaVendorAdapter());
    em.afterPropertiesSet();
    return em.getObject();
}

回答：

的配置EntityManageFactory不正确。您应该LocalContainerEntityManagerFactoryBean改用：

@Bean(name = "readingEntityManagerFactory")
public EntityManagerFactory readingEntityManagerFactory() {
    LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
    em.setPersistenceUnitName("persistence.reading");
    em.setDataSource(dataSource());
    em.setPackagesToScan("com.company");
    em.setJpaVendorAdapter(new HibernateJpaVendorAdapter());
    em.afterPropertiesSet();
    return em.getObject();
}

同样，它JpaTransactionManager也是配置错误的。应该是这样的：

@Bean(name = "readingTransactionManager")
public PlatformTransactionManager readingTransactionManager(){
    JpaTransactionManager transactionManager = new JpaTransactionManager();
    transactionManager.setEntityManagerFactory(readingEntityManagerFactory());
    return transactionManager;
}

对于读取和写入EntityManager配置，您都需要执行相同的操作。

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