Question

我浪费了太多时间，是时候问这里了，谢谢。

Frameworkds ：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中

<?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注释提前@Controller，我仍然无法得到宠物的信息，总是得到一个异常表示'未能懒得初始化角色集合：com.test.pojo.Master.pets，没有会话或会议已关闭'

请建议谢谢！

Answer 1

例外说明了一切。您正在尝试从JSP访问延迟加载的集合。执行JSP时，控制器的事务方法已返回，并且事务及其关联的会话将关闭。因此，Hibernate不再能够加载该集合。

确保从控制器加载集合，或使用OpenSessionInViewFilter或OpenSessionInViewInterceptor。

从控制器加载集合：

致电master.getPets().size()（或该集合的任何其他方法）或
致电Hibernate.initialize(master.getPets())或
将主人及其宠物加载到一个查询中：select m from Master m left join fetch m.pets where...

请注意，您的当前代码只需使用session.get()来获取ID的主文件时就会使用查询。

Answer 2

You have put **"fetch = FetchType.LAZY"**, while mapping pets, so hibernate will just load the proxies for Object "Pets" .
Either yo can make it to **"fetch = FetchType.EAGER"**, with only drawback that Hibernate will always load "Pets object" along with master object even if you do not need.
So better way is to intialize using Hibernate

**Hibernate.initialize(master.getPets()),**

使用@Transactional进行Hibernate延迟初始化异常

2 个答案: