Question

我正在使用jsp-servlet的hibernate。当我尝试访问子元素属性时，我得到以下异常：

 Servlet.service() for servlet jsp threw exception: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.ecomm.ultimatesms.messaging.persistence.pojos.Mno.startnumbers, no session or session was closed
at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:380) [:3.3.2.GA]
    at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:372) [:3.3.2.GA]
    at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:365) [:3.3.2.GA]
    at org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:108) [:3.3.2.GA]

这是我的hibernate映射文件。我正在使用hibernate-mapping default-lazy="false"

<hibernate-mapping default-lazy="false">
<class name="com.ecomm.ultimatesms.messaging.persistence.pojos.Mno" table="mno" schema="public">

    <id name="pkmnoid" type="long">
        <column name="pkmnoid" />
     <generator class="sequence">
            <param name="sequence">mno_pkmnoid_seq1</param>
        </generator>
    </id>

    <property name="name" type="string">
        <column name="name" length="45" />
    </property>

    <set name="startnumbers" table="startnumber" inverse="false" lazy="true" fetch="select" cascade="delete">
        <key>
            <column name="fkmnoid" />
        </key>
        <one-to-many class="com.ecomm.ultimatesms.messaging.persistence.pojos.Startnumber" />
    </set>
</class>
</hibernate-mapping>

Answer 1

我认为您不需要将所有连接设置为EAGER。

或者，您需要在视图模式中使用Open Session。

您可以在此处详细了解：

http://community.jboss.org/wiki/OpenSessionInView

Answer 2

授予您仍然打开会话/实体管理器的一个好方法是让一个过滤器在请求开始时注入EntityManager，而不是在执行后关闭它，因此您再也不会关心它了。看看

package com.renatogama.infra.filters;

import java.io.IOException;

import javax.persistence.EntityManager;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;

@WebFilter(urlPatterns = "/*")
public class EntityManagerFilter implements Filter {

    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        EntityManager em = new JPAUtil().getEntityManager();
        try {
            em.getTransaction().begin();
            request.setAttribute("em", em);
            chain.doFilter(request, response);
            em.getTransaction().commit();
        } catch (Exception e) {
            em.getTransaction().rollback();
            throw new ServletException(e);
        } finally {
            em.close();
        }
    }

    @Override
    public void destroy() {}

    @Override
    public void init(FilterConfig arg0) throws ServletException {}
}

Answer 3

由于您已设置lazy=true，因此必须在关闭hibernate会话之前初始化集合。这篇文章可能对您有所帮助http://community.jboss.org/wiki/LazyInitializationExceptionovercome

Answer 4

虽然您设置了lazy='true'，但您描述的是将其设置为false。因此，在访问集合（startnumbers）之前会导致问题导致会话关闭。通过设置lazy='false'（或）使用Hibernate.initialize() api在会话关闭（或）使用Open-Session-In-View模式之前加载集合来更改映射。

Hibernate org.hibernate.LazyInitializationException

4 个答案: