spring - 多对多 - 在集合上延迟初始化失败

Question

可能重复：
Spring，Hibernate - 多对多 - LazyInitializationException

我面临一个非常奇怪的问题，我无法理解。有两个实体“用户”和“联系人”。异常在 ProjectController.java 中被抛出user.getContactSet().add(contact);

我正在尝试在“用户”和“联系人”之间建立多对多关系

用户.java

   public class User {
    private Integer userID;
    private String userLoginEmail;
    private String password;
    private String userFirstName;
    .
    .

联系方式.java

   public class Contact {
   private Integer contactID;
   private String givenName;
   private String familyName;
   private String telephoneNumber;
   private String cellNumber;
   .
   .

用户.hbm.xml

<hibernate-mapping package="com.smallworks.model" schema="smallworksdb">

<class name="User" table="USERACCOUNT">
    <id column="USER_ID" length="500" name="userID">
        <generator class="increment" />
    </id>
    <property column="USER_LOGIN_EMAIL" generated="never" lazy="false" length="100" name="userLoginEmail" />
    <property column="USER_PASSWORD" generated="never" lazy="false" length="50" name="password" />
    <property column="ACTIVATION_CODE" generated="never" lazy="false" length="100" name="activationCode" />
    <property column="ACCOUNT_ACTIVATED" generated="never" lazy="false" length="1" name="accountActivated" />

    <set name="contactSet" table="USER_CONTACT" 
        inverse="false" lazy="true" fetch="select" cascade="all">
        <key column="USER_ID"/>
        <many-to-many column="CONTACT_ID" class="Contact"/>
    </set>
</class>

联系人.hbm.xml

<hibernate-mapping package="com.smallworks.model" schema="smallworksdb">
<class name="Contact" table="CONTACT">
    <id column="CONTACT_ID" length="500" name="contactID">
        <generator class="increment" />
    </id>
    <property column="GIVEN_NAME" generated="never" lazy="false" length="100" name="givenName" />
    <property column="FAMILY_NAME" generated="never" lazy="false" length="100" name="familyName" />
    <property column="TELEPHONE_NUMBER" generated="never" lazy="false" length="100" name="telephoneNumber" />
    <property column="CELL_NUMBER" generated="never" lazy="false" length="100" name="cellNumber" />
    <property column="EMAIL" generated="never" lazy="false" length="100" name="email" />
    <property column="STREET_NAME" generated="never" lazy="false" length="100" name="streetName" />
    <property column="CITY" generated="never" lazy="false" length="100" name="city" />
    <property column="STREET_ADDRESS" generated="never" lazy="false" length="100" name="streetAddress" />
    <property column="ADDRESS_LOCALITY" generated="never" lazy="false" length="100" name="addressLocality" />
    <property column="ADDRESS_REGION" generated="never" lazy="false" length="100" name="addressRegion" />
    <property column="POSTAL_CODE" generated="never" lazy="false" length="100" name="postalCode" />
    <property column="COMMENT" generated="never" lazy="false" length="100" name="comment" />

    <!-- many to many mapping with the User via User_Contact table -->
    <set name="userSet" table="USER_CONTACT" 
        inverse="true" lazy="true" fetch="select">
        <key column="USER_ID" />
        <many-to-many column="CONTACT_ID" class="Contact" />
    </set>
</class>

项目控制器.java

@RequestMapping(value = { "/project/addContact.do" }, method = RequestMethod.POST)
@ResponseBody
@JsonIgnore
public  String addContact(@ModelAttribute("UserContactAction") ContactAction contactAction, BindingResult result, HttpServletRequest request, Model model) {
    User user=(User) request.getSession().getAttribute("user");
    if(contactAction!=null){
        if(contactAction.getContact()!=null){
            Contact contact=contactAction.getContact();
            if(contact.getUserSet()==null){
                contact.setUserSet(new HashSet<User>());
            }
            user.getContactSet().add(contact);  //ERROR Gets thrown here
        }

    }else{
        System.out.println("userContactAction is NULL");
    }

例外：

    01:13:26.953 [http-bio-8080-exec-9] DEBUG o.s.w.b.a.s.HandlerMethodInvoker - Invoking request handler method: public java.lang.String com.smallworks.controller.ProjectController.addContact(com.smallworks.model.view.ContactAction,org.springframework.validation.BindingResult,javax.servlet.http.HttpServletRequest,org.springframework.ui.Model)
01:13:26.961 [http-bio-8080-exec-9] ERROR o.h.LazyInitializationException - failed to lazily initialize a collection of role: com.smallworks.model.User.contactSet, no session or session was closed
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.smallworks.model.User.contactSet, no session or session was closed
    at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:380) [hibernate-core-3.3.1.GA.jar:3.3.1.GA]
    at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:372) [hibernate-core-3.3.1.GA.jar:3.3.1.GA]
    at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:365) [hibernate-core-3.3.1.GA.jar:3.3.1.GA]
    at org.hibernate.collection.PersistentSet.add(PersistentSet.java:212) [hibernate-core-3.3.1.GA.jar:3.3.1.GA]
    at com.smallworks.controller.ProjectController.addContact(ProjectController.java:96) [ProjectController.class:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [na:1.6.0_33]
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) [na:1.6.0_33]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) [na:1.6.0_33]
    at java.lang.reflect.Method.invoke(Unknown Source) [na:1.6.0_33]
    at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176) [spring-web-3.0.5.RELEASE.jar:3.0.5.RELEASE]
    at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:426) [spring-webmvc-3.0.5.RELEASE.jar:3.0.5.RELEASE]
    at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:414) [spring-webmvc-3.0.5.RELEASE.jar:3.0.5.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790) [spring-webmvc-3.0.5.RELEASE.jar:3.0.5.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719) [spring-webmvc-3.0.5.RELEASE.jar:3.0.5.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644) [spring-webmvc-3.0.5.RELEASE.jar:3.0.5.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560) [spring-webmvc-3.0.5.RELEASE.jar:3.0.5.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:647) [servlet-api.jar:na]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728) [servlet-api.jar:na]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) [catalina.jar:7.0.33]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) [catalina.jar:7.0.33]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222) [catalina.jar:7.0.33]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123) [catalina.jar:7.0.33]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) [catalina.jar:7.0.33]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171) [catalina.jar:7.0.33]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99) [catalina.jar:7.0.33]

我很困惑，为什么会出现这个异常，任何形式的帮助都将不胜感激。我还尝试将用户和联系人带走，而是尝试在员工和会议之间做多对多（只是创建了一些独立的对象），然后一切正常。请帮忙...