java - Hibernate 带有 @Transactional 的延迟初始化异常

Question

我在这上面浪费了太多时间，是时候在这里问一下了，谢谢。

框架:SpringMVC 4 + Hibernate 3.6.0

我的期望:在 jsp 页面上显示 Pojo(一对多)对象

我的配置

1.applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="dataSource" class="org.logicalcobwebs.proxool.ProxoolDataSource">
        <property name="driver" value="com.mysql.jdbc.Driver"/>
        <property name="driverUrl" value="jdbc:mysql://localhost:3306/xxx"/>
        <property name="user" value="-"/>
        <property name="password" value="-"/>
        <property name="maximumConnectionCount" value="10"/>
        <property name="minimumConnectionCount" value="5"/>
    </bean>
    <bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
        <property name="packagesToScan" value="com.test.pojo"/>
        <property name="dataSource" ref="dataSource"/>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.hbm2ddl.auto">update</prop>
                <!-- auto generate table -->
            </props>
        </property>
    </bean>
</beans>

2.dispatcher-servlet.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:tx="http://www.springframework.org/schema/tx"

       xmlns:task="http://www.springframework.org/schema/task"

       xsi:schemaLocation="http://www.springframework.org/schema/beans
                           http://www.springframework.org/schema/beans/spring-beans.xsd
                           http://www.springframework.org/schema/mvc 
                           http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd 
                           http://www.springframework.org/schema/context
                           http://www.springframework.org/schema/context/spring-context-3.1.xsd
                           http://www.springframework.org/schema/tx 
                           http://www.springframework.org/schema/tx/spring-tx-3.1.xsd

                           http://www.springframework.org/schema/task
                           http://www.springframework.org/schema/task/spring-task-3.0.xsd">



    <bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager">
        <property name="sessionFactory" ref="sessionFactory" />
    </bean>

    <tx:annotation-driven transaction-manager="transactionManager" />

    <task:annotation-driven />

    <mvc:annotation-driven />

    <context:component-scan base-package="com.test.module" />

    <!--HandlerMapping-->
    <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping"/>

    <!--HandlerAdapter-->
    <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter"/>

    <!--ViewResolver -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="viewClass" value="org.springframework.web.servlet.view.JstlView" />
        <property name="prefix" value="/views/" />
        <property name="suffix" value=".jsp" />
    </bean>

</beans>

3. Controller

@Transactional
@Controller
public class TESTS {

    @Resource(name="sessionFactory")
    private SessionFactory sessionFactory;

    @RequestMapping("/hello")
    public ModelAndView test(){
        ModelAndView mv = new ModelAndView();
        mv.setViewName("/hello");
        mv.addObject("master", (Master) sessionFactory.getCurrentSession().createQuery("from Master where master_id = 1").uniqueResult());
        return mv;
    }
}

4.Pojos

public class Master {
    @Id
    @GeneratedValue
    private Integer master_id;
    private String master_name;

    @OneToMany(fetch = FetchType.LAZY, mappedBy="master", cascade = CascadeType.ALL,orphanRemoval=true)
    private List<Pet> pets;
}

public class Pet {

    @Id
    @GeneratedValue
    private Integer id;

    private String name;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "master_id", nullable = false)
    private Master master;
}

即使我把@Transnational注解放在@Controller前面，我仍然无法获取宠物的信息，总是出现异常“无法延迟初始化角色集合:com.test.pojo.Master.pets，没有 session ”或 session 已关闭'

请指教，谢谢!

Answer 1

异常说明了一切。您正在尝试从 JSP 访问延迟加载的集合。当执行 JSP 时， Controller 的事务方法已返回，并且事务及其关联的 session 将关闭。因此 Hibernate 无法再加载该集合。

确保从 Controller 加载集合，或使用 OpenSessionInViewFilter 或 OpenSessionInViewInterceptor。

从 Controller 加载集合:

• 调用master.getPets().size()(或集合的任何其他方法)，或者
• 调用Hibernate.initialize(master.getPets())，或
• 在单个查询中加载主人及其宠物:select m from Master m left join fetch m.pets where...

请注意，当您当前的代码应该简单地使用 session.get() 通过 ID 获取 Master 时，它会使用查询。