hibernate配置多对多映射问题

Question

 以下是两个hibernate映射文件：

Activity:

<?xml version="1.0" encoding="gb2312"?>
<!DOCTYPE hibernate-mapping PUBLIC   
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"  
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> 
<hibernate-mapping package="com.ywt.domain">  
    <class name="Activity" table="activity" lazy="true">  
        <!-- id元素定义持久化类的标识属性 -->  
        <id name="id">
            <!-- 指定主键生成策略 -->  
            <generator class="native" />  
        </id>  
        <!-- property元素定义常规属性 -->  
        <property name="name" not-null="true"/>  
        <property name="time" not-null="true"/>  
        <property name="imageurl" not-null="true"/>  
        <property name="hostone" not-null="true"/>  
        <property name="hosttwo" not-null="true"/>  
        <property name="introduce" not-null="true"/>  
        <property name="problem" />  
        <property name="award" />  
        <property name="schedule" />  
        <property name="number" />  
        <property name="status" not-null="true"/>  
        <set name="studentSet" table="activity_student" inverse="true">
        	<key>
        		<column name="A_ID"></column>
        	</key>
        	<many-to-many class="Student" column="S_ID" ></many-to-many>
        </set>  
    </class>  
</hibernate-mapping>

Student:

<?xml version="1.0" encoding="gb2312"?>
<!DOCTYPE hibernate-mapping PUBLIC   
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"  
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> 
<hibernate-mapping package="com.ywt.domain">  
    <!-- 每个class元素对应一个持久化对象 lazy="true" 代表加载延迟 对象A对对象B引用才会用到-->  
    <class name="Student" table="student" lazy="true">  
        <!-- id元素定义持久化类的标识属性 -->  
        <id name="id">
            <!-- 指定主键生成策略 -->  
            <generator class="native" />  
        </id>  
        <!-- property元素定义常规属性 -->  
        <property name="username" not-null="true"/>  
        <property name="password" not-null="true"/>  
        <property name="name" not-null="true"/>  
        <property name="sex" not-null="true"/>  
        <property name="major" not-null="true"/>  
        <property name="academy" not-null="true"/>  
        <property name="tel" />  
        <property name="coin"/>  
        <property name="activities" />  
        <property name="honor" /> 
        <set name="activitySet" table="activity_student">
        	<key>
        		<column name="S_ID"></column>
        	</key>
        	<many-to-many class="Activity" column="A_ID"></many-to-many>
        </set>  
    </class>  
</hibernate-mapping>

所出现的问题是：只要Activity映射文件中一加set集合就报如下错误（Student映射文件中加set不报错，已确认各属性书写没错误）：

严重: Servlet.service() for servlet [mvc] in context with path [/dxshdw] threw exception [Handler processing failed; nested exception is java.lang.NoClassDefFoundError: Could not initialize class com.ywt.util.HibernateUtil] with root cause

java.lang.NoClassDefFoundError: Could not initialize class com.ywt.util.HibernateUtil

其中HibernateUtil是获取session工厂的类

Answer 1

关联关系维护出了问题

Answer 2

Could not initialize class com.ywt.util.HibernateUtil] 这个类有问题吧

Answer 3

class com.ywt.util.HibernateUtil这个工具类就找不见，看是servlet中忘了导入还是其他