java - JPA 连接与 EntityManager 关闭

标签 java spring hibernate jpa entitymanager

请原谅这篇文章可能格式不正确，因为我以前从未在这里发布过。我正在运行一个 Spring MVC Web 服务，它调用多个使用 JPA/hibernate 与 SQL Server 数据库交互的 DAO。 Web 服务运行一段时间后，与数据库的连接似乎已关闭。

DAO 类之一的示例如下:

@Repository
public class OceanClientDaoImpl {

// Create entity manager objects that will talk to the database
private EntityManagerFactory entityManagerFactory;

/**
 * Load all clients in the database. Return as ClientLight objects.
 * 
 * @return List of ClientLight objects.
 */
public List<Client> loadClients() 
{
    EntityManager entityManager = entityManagerFactory.createEntityManager();
    entityManager.getTransaction().begin();
    List<?> clients = 
            entityManager.createNativeQuery("select id, clientname, industry, logo, slug from client", 
                    Client.class).getResultList();
    entityManager.getTransaction().commit();
    entityManager.close();
    return Client.getCheckedList(clients);
}
}

entityManagerFactory 通过 spring 通过以下方式注入(inject):

<bean id="dataSource" class="org.apache.tomcat.jdbc.pool.DataSource">
    <property name="driverClassName"     value="com.microsoft.sqlserver.jdbc.SQLServerDriver" />
    <property name="url" value="url" />
    <property name="username" value="user" />
    <property name="password" value="pw" />
</bean>

<bean
    class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"
    id="entityManagerFactory">
    <property name="dataSource" ref="dataSource" />
</bean>

<context:component-scan base-package="com.theocean.dao">
    <context:include-filter type="annotation"
        expression="org.springframework.stereotype.Repository" />
</context:component-scan>

<bean class="org.springframework.orm.jpa.JpaTransactionManager"
    id="transactionManager">
    <property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>

<bean id="oceanClientDaoImpl" class="com.theocean.dao.OceanClientDaoImpl">
    <property name="entityManagerFactory" ref="entityManagerFactory"/>
</bean>

当我第一次启动该应用程序时，一切正常。应用服务器是Tomcat。但是，应用程序运行一段时间后，对服务器的请求开始收到此错误:

> SEVERE: Servlet.service() for servlet [spring] in context with path [/OceanWebService] threw exception [Request processing failed; nested exception is javax.persistence.PersistenceException: org.hibernate.TransactionException: JDBC begin failed: ] with root cause
com.microsoft.sqlserver.jdbc.SQLServerException: SQL Server did not return a response. The connection has been closed.
    at com.microsoft.sqlserver.jdbc.SQLServerConnection.terminate(SQLServerConnection.java:1667)
    at com.microsoft.sqlserver.jdbc.SQLServerConnection.terminate(SQLServerConnection.java:1654)
    at com.microsoft.sqlserver.jdbc.TDSReader.readPacket(IOBuffer.java:4844)
    at com.microsoft.sqlserver.jdbc.TDSCommand.startResponse(IOBuffer.java:6154)
    at com.microsoft.sqlserver.jdbc.TDSCommand.startResponse(IOBuffer.java:6106)
    at com.microsoft.sqlserver.jdbc.SQLServerConnection$1ConnectionCommand.doExecute(SQLServerConnection.java:1756)
    at com.microsoft.sqlserver.jdbc.TDSCommand.execute(IOBuffer.java:5696)
    at com.microsoft.sqlserver.jdbc.SQLServerConnection.executeCommand(SQLServerConnection.java:1715)
    at com.microsoft.sqlserver.jdbc.SQLServerConnection.connectionCommand(SQLServerConnection.java:1761)
    at com.microsoft.sqlserver.jdbc.SQLServerConnection.setAutoCommit(SQLServerConnection.java:1901)
    at sun.reflect.GeneratedMethodAccessor32.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.apache.tomcat.jdbc.pool.ProxyConnection.invoke(ProxyConnection.java:126)
    at org.apache.tomcat.jdbc.pool.JdbcInterceptor.invoke(JdbcInterceptor.java:99)
    at org.apache.tomcat.jdbc.pool.DisposableConnectionFacade.invoke(DisposableConnectionFacade.java:58)
    at com.sun.proxy.$Proxy32.setAutoCommit(Unknown Source)
    at org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:87)
    at org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1473)
    at org.hibernate.ejb.TransactionImpl.begin(TransactionImpl.java:60)
    at com.theocean.dao.OceanClientDaoImpl.loadClients(OceanClientDaoImpl.java:52)
    at com.theocean.service.ExperienceClientService.loadClientsLight(ExperienceClientService.java:30)
    at com.theocean.web.ExperienceController.loadClientsLight(ExperienceController.java:30)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176)
    at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:436)
    at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:424)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:669)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:574)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:947)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1009)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
SEVERE: Servlet.service() for servlet [spring] in context with path [/OceanWebService]     threw exception [Request processing failed; nested exception is javax.persistence.PersistenceException: org.hibernate.TransactionException: JDBC begin failed: ] with root cause
com.microsoft.sqlserver.jdbc.SQLServerException: SQL Server did not return a response. The connection has been closed.
    at com.microsoft.sqlserver.jdbc.SQLServerConnection.terminate(SQLServerConnection.java:1667)
    at com.microsoft.sqlserver.jdbc.SQLServerConnection.terminate(SQLServerConnection.java:1654)
    at com.microsoft.sqlserver.jdbc.TDSReader.readPacket(IOBuffer.java:4844)
    at com.microsoft.sqlserver.jdbc.TDSCommand.startResponse(IOBuffer.java:6154)
    at com.microsoft.sqlserver.jdbc.TDSCommand.startResponse(IOBuffer.java:6106)
    at com.microsoft.sqlserver.jdbc.SQLServerConnection$1ConnectionCommand.doExecute(SQLServerConnection.java:1756)
    at com.microsoft.sqlserver.jdbc.TDSCommand.execute(IOBuffer.java:5696)
    at com.microsoft.sqlserver.jdbc.SQLServerConnection.executeCommand(SQLServerConnection.java:1715)
    at com.microsoft.sqlserver.jdbc.SQLServerConnection.connectionCommand(SQLServerConnection.java:1761)
    at com.microsoft.sqlserver.jdbc.SQLServerConnection.setAutoCommit(SQLServerConnection.java:1901)
    at sun.reflect.GeneratedMethodAccessor32.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.apache.tomcat.jdbc.pool.ProxyConnection.invoke(ProxyConnection.java:126)
    at org.apache.tomcat.jdbc.pool.JdbcInterceptor.invoke(JdbcInterceptor.java:99)
    at org.apache.tomcat.jdbc.pool.DisposableConnectionFacade.invoke(DisposableConnectionFacade.java:58)
    at com.sun.proxy.$Proxy32.setAutoCommit(Unknown Source)
    at org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:87)
    at org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1473)
    at org.hibernate.ejb.TransactionImpl.begin(TransactionImpl.java:60)
    at com.theocean.dao.OceanClientDaoImpl.loadClients(OceanClientDaoImpl.java:52)
    at com.theocean.service.ExperienceClientService.loadClientsLight(ExperienceClientService.java:30)
    at com.theocean.web.ExperienceController.loadClientsLight(ExperienceController.java:30)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176)
    at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:436)
    at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:424)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:669)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:574)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:947)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1009)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

因此，连接正在关闭。显然，无论是注入(inject)方法还是处理错误的方法等，实现都有问题。所以，问题是 - 正确的方法是什么？如何避免连接关闭错误？非常感谢。

最佳答案

我认为可能发生的情况是，当发生错误时，某些 DAO 使数据库事务保持打开状态。

上面的示例 DAO 对数据库事务进行编程管理，但不处理回滚场景。这是执行此操作的 DAO 实现的示例:

    MyService {

   private EntityManagerFactory emf;

   public void myMethod() {
       EntityManager em = emf.createEntityManager();
       EntityTransaction tx = em.getTransaction();
       MyDaoA myDaoA = new MyDaoA(em);
       MyDaoB myDaoB = new MyDaoB(em);
       try {
           tx.begin();
           myDaoA.doSomething();
           myDaoB.doSomething();
           tx.commit();
       } catch(Exception e) {
           tx.rollback();
       }
    }
}

所有进行编程式事务管理的 DAO 都应该使用此模式，否则迟早事务将不会回滚，这可能会导致问题。

实现 DAO 的一种更频繁且不易出错的方法是直接注入(inject)实体管理器:

MyService {

   @PersistenceContext
   private EntityManager em;

   @Autowired
   private MyDaoA myDaoA;

   @Autowired
   private MyDaoB myDaoB;

   @Transactional
   public void myMethod() {
      myDaoA.doSomething();
      myDaoB.doSomething();
    }
}

注入(inject)EntityManagerFactory并进行手动事务管理应保留在特殊情况下，并且默认使用@Transactional。

关于java - JPA 连接与 EntityManager 关闭，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/19848794/

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