java - EntityManager 使用依赖注入导致的死锁
问题描述
我正在开发一个带有 REST 服务的应用程序。我正在使用依赖注入来注入 EntityManagerFactory。我有一个繁重的过程，我想使用线程，但是在使用 EntityManager 时它给了我一个死锁。编码：
注意：所有代码已被简化并重命名类以解释问题
持久性.xml：
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1"
xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
<persistence-unit name="mypersistenceunit" transaction-type="RESOURCE_LOCAL">
<provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
<!-- Entities -->
<properties>
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect" />
<property name="hibernate.show_sql" value="true" />
<property name="hibernate.event.merge.entity_copy_observer" value="allow" />
<property name="hibernate.connection.autocommit" value="false"/>
</properties>
</persistence-unit>
</persistence>
应用程序上下文.xml：
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:jee="http://www.springframework.org/schema/jee"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-4.0.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx.xsd
"
default-autowire="byName">
<context:property-placeholder location="classpath:database.properties"/>
<bean id="logDao" class="my.package.example.dao.LogDao">
<property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>
<bean id="extractDataDao" class="my.package.example.source.ExtractDataDao">
<property name="completeDatabaseModel" ref="completeDatabaseModel"/>
</bean>
<bean id="completeDatabaseModel" class="my.package.example.source.CompleteDatabaseModel">
<property name="logDao" ref="logDao" />
</bean>
<bean id="fill" class="my.package.example.services.impl.FillDatabaseServiceImpl">
<property name="extractDataDao" ref="extractDataDao" />
</bean>
<!-- Configuracion de acceso a base de datos -->
<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="myDataSource" />
<property name="persistenceUnitName" value="mypersistenceunit"/>
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
<property name="showSql" value="false" />
<property name="databasePlatform" value="org.hibernate.dialect.MySQLDialect" />
</bean>
</property>
</bean>
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="com.mysql.jdbc.Driver" />
</bean>
<bean id="myDataSource" parent="dataSource">
<property name="url" value="${jdbc.url}" />
<property name="username" value="${jdbc.username}" />
<property name="password" value="${jdbc.password}" />
</bean>
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>
<tx:annotation-driven transaction-manager="transactionManager" />
</beans>
FillDatabaseServiceImpl.java：
public class FillDatabaseServiceImpl implements FillDatabaseService {
private ExtractDataDao extractDataDao;
private final static Gson gson = new Gson();
@Override
public Response start() {
ResultDto resultDto = new ResultDto();
Thread thread = new Thread(this.extractDataDao);
thread.start();
resultDto.setData("Process has started");
return Response.ok(gson.toJson(resultDto)).build();
}
public void setExtractDataDao(ExtractDataDao extractDataDao) {
this.extractDataDao = extractDataDao;
}
}
ExtractDataDao.java：
public class ExtractDataDao implements Runnable {
private CompleteDatabaseModel completeDatabaseModel;
@Override
public void run() {
// Very simplifed class
int numThreads = 5;
ExecutorService executor = Executors.newFixedThreadPool(numThreads);
for (int j = 0; j < numThreads; j++) {
executor.execute(this.completeDatabaseModel);
}
}
public void setCompleteDatabaseModel(CompleteDatabaseModel completeDatabaseModel) {
this.completeDatabaseModel = completeDatabaseModel;
}
}
CompleteDatabaseModel.java
public class CompleteDatabaseModel implements Runnable {
private EntityManagerFactory entityManagerFactory;
private LogDao logDao;
@Override
public void run() {
// Very simplified class
EntityManager entityManager = null;
try {
entityManager = this.entityManagerFactory.createEntityManager();
...
this.logDao.insertLog("Test message", CATEGORY);
...
this.getCountry(entityManager, "country")
} finally {
entityManager.close();
}
}
private synchronized Country getCountry(final EntityManager entityManager, String strCountry) {
Country country = Country.getCountryByCountry(entityManager, strCountry);
if (country == null) {
country = ImdbToMovieDatabase.convert(strCountry, Country.class);
entityManager.getTransaction().begin();
entityManager.persist(country);
entityManager.getTransaction().commit();
country = Country.getCountryByCountry(entityManager, strCountry);
}
return country;
}
public void setLogDao(final LogDao logDao) {
this.logDao = logDao;
}
}
以及引起死锁的类：
日志道.java：
public class LogDao {
private EntityManagerFactory entityManagerFactory;
public void insertLog(final String message, final Category.CategoryName categoryName) {
Log log = new Log();
EntityManager entityManager = this.entityManagerFactory.createEntityManager();
try {
entityManager.getTransaction().begin();
Category category = Category.getCategoryByName(entityManager, categoryName.name());
log.setCategory(category);
log.setLog(message);
entityManager.persist(log); // // Cause of deadlock in Thread-1 (for example)
entityManager.getTransaction().commit();
} catch (Exception e) {
logger.error("Error persisting log [" + message + "]", e);
entityManager.getTransaction().rollback();
} finally {
if (entityManager != null) {
entityManager.close();
}
}
}
public void setEntityManagerFactory(final EntityManagerFactory entityManagerFactory) {
this.entityManagerFactory = entityManagerFactory;
}
}
实体.java：
public static Country getCountryByCountry(final EntityManager entityManager, final String strCountry) {
Country country = null;
try {
TypedQuery<Country> typedQuery =
entityManager.createQuery(
"SELECT c FROM Country c WHERE country = ?",
Country.class);
typedQuery.setParameter(1, strCountry);
country = typedQuery.getSingleResult(); // Cause of deadlock in Thread-2 (for example)
} catch (NoResultException e) {
System.out.println("No data found for " + strCountry);
} catch (Exception e) {
e.printStackTrace();
}
return country;
}
也许private synchronized Country getCountry是在挑起僵局？我认为我不应该，因为 logDao 已经注入了自己的 EntityManagerFactory
我可以使用连接池吗？
提前致谢。