java 使用多个数据源时，Spring 中的多个实体管理器问题
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Multiple Entity Manager issue in Spring when using more than one datasource
提问by Sameer Malhotra
I have two entity managers in my applicationContext.xmlwhich corresponds to two different databases. I can easily query database1with entityManager1, but when I try to access database2with entityManager2, I am not getting any results. I am using Spring+Hibernate+JPA.
我有两个实体管理器，applicationContext.xml它们对应于两个不同的数据库。我可以很容易地查询database1用entityManager1，但是当我试图访问database2与entityManager2，我没有得到任何结果。我正在使用 Spring+Hibernate+JPA。
Here is my ApplicationContext.xml
这是我的 ApplicationContext.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans default-autowire="byName"
xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd">
<bean
class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor" />
<bean id="entityManagerFactory"
class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
<property name="database" value="INFORMIX" />
<property name="showSql" value="true" />
</bean>
</property>
<property name="persistenceUnitManager" ref="persistenceUnitManager" />
<property name="persistenceUnitName" value="PU1" />
</bean>
<bean id="entityManagerFactory2"
class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource2" />
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
<property name="database" value="INFORMIX" />
<property name="showSql" value="true" />
</bean>
</property>
<property name="persistenceUnitManager" ref="persistenceUnitManager" />
<property name="persistenceUnitName" value="PU2" />
</bean>
<!-- Data Sources -->
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"
destroy-method="close">
<property name="driverClassName" value="com.ibm.db2.jcc.DB2Driver" />
<property name="url"
value="jdbc:db2://HOST_NAME:PORT_NO/DB_NAME:INFORMIXSERVER=SERVER_NAME;DELIMIDENT=y;" />
<property name="username" value="username" />
<property name="password" value="password" />
<property name="minIdle" value="2" />
</bean>
<bean id="dataSource2" class="org.apache.commons.dbcp.BasicDataSource"
destroy-method="close">
<property name="driverClassName" value="com.ibm.db2.jcc.DB2Driver" />
<property name="url"
value="jdbc:db2://HOST_NAME:PORT_NO/DB_NAME2:INFORMIXSERVER=SERVER_NAME;DELIMIDENT=y;" />
<property name="username" value="username" />
<property name="password" value="password" />
<property name="minIdle" value="2" />
</bean>
<bean
class="org.springframework.beans.factory.config.MethodInvokingFactoryBean"
lazy-init="false">
<property name="targetObject" ref="dataSource" />
<property name="targetMethod" value="addConnectionProperty" />
<property name="arguments">
<list>
<value>characterEncoding</value>
<value>UTF-8</value>
</list>
</property>
</bean>
<bean
class="org.springframework.beans.factory.config.MethodInvokingFactoryBean"
lazy-init="false">
<property name="targetObject" ref="dataSource2" />
<property name="targetMethod" value="addConnectionProperty" />
<property name="arguments">
<list>
<value>characterEncoding</value>
<value>UTF-8</value>
</list>
</property>
</bean>
<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate"
scope="prototype">
<property name="dataSource" ref="dataSource" />
</bean>
<bean id="persistenceUnitManager"
class="org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager">
<property name="persistenceXmlLocations">
<list>
<value>classpath*:META-INF/persistence.xml</value>
<value>classpath*:META-INF/persistence2.xml</value>
</list>
</property>
<property name="dataSources">
<map>
<entry key="localDataSource" value-ref="dataSource" />
<entry key="dataSource2" value-ref="dataSource2" />
</map>
</property>
<property name="defaultDataSource" ref="dataSource" />
</bean>
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>
<bean id="transactionManager2" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory2" />
</bean>
<tx:annotation-driven transaction-manager="transactionManager" />
<tx:annotation-driven transaction-manager="transactionManager2" />
<!-- MORE Action and DAO beans -->
</beans>
This is my service layer code which works fine with enityManager1:
这是我的服务层代码，适用于enityManager1：
@Transactional
public class StatesDAO implements IStatesDAO {
private EntityManager em;
@PersistenceContext(unitName = "PU1")
public void setEntityManager(EntityManager em) {
this.em = em;
}
private EntityManager getEntityManager() {
return em;
}
@SuppressWarnings("unchecked")
public List<States> findAll() {
logger.info("finding all States instances");
try {
final String queryString = "select model from States model";
Query query = getEntityManager().createQuery(queryString);
return query.getResultList();
} catch (RuntimeException re) {
throw re;
}
}
}
My two persitence.xmlfiles look like this:
我的两个persitence.xml文件如下所示：
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0"
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_1_0.xsd">
<persistence-unit name="PU1" transaction-type="RESOURCE_LOCAL">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<class>com.jpa.entity.States</class>
</persistence-unit>
</persistence>
and
和
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0"
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_1_0.xsd">
<persistence-unit name="PU2" transaction-type="RESOURCE_LOCAL">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<class>com.jpa.other.entity.States</class>
</persistence-unit>
</persistence>
If I change my service layer (as shown below), I get no results. Basically the size of the list is zero:
如果我更改我的服务层（如下所示），我将不会得到任何结果。基本上列表的大小为零：
@Transactional
public class StatesDAO implements IStatesDAO {
private EntityManager em;
@PersistenceContext(unitName = "PU2")
public void setEntityManager(EntityManager em) {
this.em = em;
}
private EntityManager getEntityManager() {
return em;
}
@SuppressWarnings("unchecked")
public List<com.jpa.other.entity.States> findAll() {
logger.info("finding all States instances");
try {
final String queryString = "select model from States model";
Query query = getEntityManager().createQuery(queryString);
return query.getResultList();
} catch (RuntimeException re) {
throw re;
}
}
}
So basically you can see is that I have two entities(States) with exactly same structure and in order to differentiate from each other I have put them into separate packages
所以基本上你可以看到我有两个具有完全相同结构的实体（状态），为了彼此区分，我将它们放入单独的包中
According to my knowledge I am not doing anything crazy here but still it doesn't seem to be working. How is this problem caused and how can I solve this?
据我所知，我在这里没有做任何疯狂的事情，但它似乎仍然不起作用。这个问题是如何引起的，我该如何解决？
Follow-up:One thing I forgot to mention is that even though there are two different databases but the database server name is same. I don't know if this could be a useful information.So thought of sharing it.
跟进：我忘记提及的一件事是，即使有两个不同的数据库，但数据库服务器名称是相同的。我不知道这是否是一个有用的信息。所以想分享它。
This is the exception I am getting now:
这是我现在得到的例外：
16:24:44,732 INFO [STDOUT] Hibernate: select state0_.state as col_0_0_ from states state0_
16:24:44,753 WARN [JDBCExceptionReporter] SQL Warning: 36106, SQLState: 01I01
16:24:44,753 WARN [JDBCExceptionReporter] IDS SQL Warning: SQLCODE=36106, SQLSTATE=01I01, SQLERRMC=0;819;informix;;IDS/NT32;1;1;0;819;0;, DRIVER=4.7.85
回答by atrain
I've hit the same exact issue, but with multiple Hibernate session factories: 2 DBs with the same structure, I didn't want to have 2 identical sets of DAOs, etc. While my experience was with Hibernate, I suspect you could use the same solution: Spring's AbstractRoutingDataSource. It allows you to configure your app to determine at runtime which data source to use, based on a value set on the ThreadLocal. See http://blog.springsource.com/2007/01/23/dynamic-datasource-routing/for an introduction. What ends up happening is that the dataSourceref in your factory will point not at a hard-coded dataSourcebean, but at the AbstractRoutingDataSource. To set the toggle per-thread, use an @Aspect to determine which DB to hit.
我遇到了同样的问题，但是有多个 Hibernate 会话工厂：2 个结构相同的 DB，我不想有 2 组相同的 DAO，等等。虽然我的经验是 Hibernate，但我怀疑你可以使用相同的解决方案：Spring 的AbstractRoutingDataSource. 它允许您配置您的应用程序，以在运行时根据ThreadLocal. 有关介绍，请参阅http://blog.springsource.com/2007/01/23/dynamic-datasource-routing/。最终发生的事情是dataSource你工厂中的ref 将不会指向一个硬编码的dataSourcebean，而是指向AbstractRoutingDataSource. 要设置每个线程的切换，请使用 @Aspect 来确定要命中哪个 DB。
