关于json和hibernate延迟加载的问题

log4j:WARN No appenders could be found for logger (org.apache.http.impl.conn.BasicClientConnectionManager). log4j:WARN Please initialize the log4j system properly. 关于json和hibernate延迟加载的问题 求教各位大大。。。
这是action的代码：

package org.demo.action;


import java.io.PrintWriter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import net.sf.json.JSONArray;
import org.apache.struts2.ServletActionContext;
import org.demo.service.ISpecialtyService;
public class SpecialtyAction {

 private ISpecialtyService specialtyservice;
 public String getSpecialty(){

  HttpServletRequest request = ServletActionContext.getRequest();
  String collegeName=request.getParameter("collegeName");
  HttpServletResponse response = ServletActionContext.getResponse(); 
     response.setCharacterEncoding("UTF-8");      
     PrintWriter out;   
     try{

     JSONArray jsonlist=JSONArray.fromObject(specialtyservice.getSpecialty(collegeName));
  out = response.getWriter();
  out.println(jsonlist); 
  out.flush();    
        out.close(); 
 } catch (Exception e) {

  // TODO Auto-generated catch block

  e.printStackTrace();
 }  

  return null;
 }

 public ISpecialtyService getSpecialtyservice() {

  return specialtyservice;
 }

 public void setSpecialtyservice(ISpecialtyService specialtyservice) {

  this.specialtyservice = specialtyservice;
 }

}

这是dao层的代码：

package org.demo.dao.impl;


import java.util.List;
import org.demo.dao.BaseDAO;
import org.demo.dao.ISpecialtyDAO;
import org.demo.vo.Specialty;
import org.hibernate.Hibernate;
import org.hibernate.Query;
import org.hibernate.Session;
public class SpecialtyDAO extends BaseDAO implements ISpecialtyDAO{

 public List<Specialty> getSpecialty(String college) {

  Session session=getSession();
  String hql="from Specialty s where s.college.name='"+college+"'";
  Query query=session.createQuery(hql);
  List<Specialty> specialty=query.list();
  if (specialty != null && !specialty.isEmpty()){  
         for (Specialty spe:specialty) {  
          Hibernate.initialize(spe.getCollege());
         }  
  }

  session.close();
  return specialty;
 }

}

这是实体的的配置文件：
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 
    Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
    <class name="org.demo.vo.Specialty" table="specialty" catalog="ws_demo">
        <id name="id" type="java.lang.Integer">
            <column name="id" />
            <generator class="native" />
        </id>
        <many-to-one name="college" class="org.demo.vo.College" fetch="select" >
            <column name="college" not-null="true" />
        </many-to-one>
        <property name="name" type="java.lang.String">
            <column name="name" not-null="true" />
        </property>
        <property name="desc" type="java.lang.String">
            <column name="desc" not-null="true" />
        </property>
    </class>
</hibernate-mapping>

我在dao层session关闭前已经加载了关联实体college属性，在action层代码里可以查询关联实体的属性，但是转换成json还是报错。
net.sf.json.JSONException: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: org.demo.vo.College.specialties, no session or session was closed