Java 使用 Spring 时如何注入多个 JPA EntityManager（持久化单元）

How to inject multiple JPA EntityManager (persistence units) when using Spring

提问by Xorty

I need to use one database for queries (non-modifying) and one for commands (modifying). I am using Spring Data JPA, so I have two configuration classes:

我需要将一个数据库用于查询（非修改）和一个用于命令（修改）。我使用的是 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();
    }

}

In my repository I sometimes need to decide with EntityManager to use like so:

在我的存储库中，我有时需要决定使用 EntityManager 像这样使用：

@Repository
public class UserReadingRepository {

    @PersistenceContext(unitName = "persistence.reading")
    private EntityManager em;

    // some useful queries here
}

I am using persistence unit's name as defined in my persistence.xml:

我正在使用在我的persistence.xml 中定义的持久性单元的名称：

<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>

Spring throws org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'persistence.reading'is defined. Oddly, it looks like Spring tries to instantiate a beanwith persistence unit name? Did I misconfigure something?

Spring throwsorg.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'persistence.reading'已定义。奇怪的是，看起来 Spring 试图用持久性单元名称实例化一个 bean？我是否配置错误？

UPDATE: When I remove unitName = "persistence.reading"from @PersistenceContext annotation, I will get following error instead: org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [javax.persistence.EntityManagerFactory] is defined: expected single matching bean but found 2: readingEntityManagerFactory,writingEntityManagerFactory

更新：当我unitName = "persistence.reading"从 @PersistenceContext 注释中删除时，我会收到以下错误： org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [javax.persistence.EntityManagerFactory] is defined: expected single matching bean but found 2: readingEntityManagerFactory,writingEntityManagerFactory

UPDATE 2: Rohit suggested (in the comment) to wire EntityManagerFactoryinstead. So I tried to do the following:

更新 2：Rohit 建议（在评论中）EntityManagerFactory改为连接。所以我尝试执行以下操作：

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

but Spring only reports: org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'persistence.reading' is defined

但 Spring 只报告： org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'persistence.reading' is defined

FINAL FIX: Thanks to Vlad's answer, I was able to update the code to use the following (just make sure you define your dataSourcebean as well):

最终修复：感谢 Vlad 的回答，我能够更新代码以使用以下内容（只需确保您也定义了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();
}

采纳答案by Vlad Mihalcea

The EntityManageFactoryis not properly configured. You should use a LocalContainerEntityManagerFactoryBeaninstead:

在EntityManageFactory没有正确配置。您应该使用 aLocalContainerEntityManagerFactoryBean代替：

@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();
}

Also the JpaTransactionManageris miss-configured too. It should be something like:

也JpaTransactionManager配置错误。它应该是这样的：

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

You need to do the same for both the reading and the writing EntityManager configurations.

您需要对读取和写入 EntityManager 配置执行相同的操作。