hibernate 动态查询

我做得一个struts+hibernate的项目，有一个问题是这样的：student(学生持久化类),team(班级持久化类),academy(学院持久化类)，student和team是一对多关系，team和Academy是一对多关系,student和Academy没有直接的关系。现在我想做一个动态查询，其中一段代码是这样的。


下面的代码很多，但是粗略看一下就行，不用一句一句的看
/**
* 根据条件查询
*/
public List byStudent(String sno,String sname,String classid,int academyid){

Criteria critera = getSession().createCriteria(Student.class);//里面是一个class对象，而不是HQL
if(sno!=null&&!sno.equals("")){//如果equals在前面的话，容易报 nullpoint 异常
critera.add(Restrictions.like("sno", sno,MatchMode.ANYWHERE));
//如果是进行模糊查询的话，就要加一个参数，MatchMode.ANYWHERE ，否则就不能进行模糊查询
}
if(sname!=null&&!sname.equals("")){
critera.add(Restrictions.like("sname", sname,MatchMode.ANYWHERE));
}
if(address!=null&&!address.equals("")){
critera.add(Restrictions.like("address", address,MatchMode.ANYWHERE));
}
if(classid!=0){
critera.add(Restrictions.eq("classes.cid",new Integer(classid)));
}
if(academyid!=0){
critera.add(Restrictions.like("academyid",new Integer(academyid));
}
return critera.list();
}

问题是这样的，那个academyid也是需要进行动态查询的，但是critera.add(Restrictions.eq("？",new Integer(academyid)));这里的问好我不知道该填写什么,请大家帮一下

问题补充：
别人贴出的代码都是截图，具体是怎样实现的？
问题补充：

public class Student implements java.io.Serializable {

	private String id;  			//hibernate主键id 学号
	private String name;			//学生姓名	
	private String psw;				//登录密码
       private Team team;				//所在班级
    private Grade grade;			//所在年级
    private Approve approve;		//学生是否通过素质拓展认证
    private ColumnOne columnOne;

问题补充：

public class Team implements java.io.Serializable {

	private String id;
	
	private String name;
	
	private Set<Student> students = new HashSet<Student>();
	
	private Academy academy;

问题补充：

public class Academy  implements java.io.Serializable {

	private String id;
	
	private String name;
	
	private Set<Admin> admins = new HashSet<Admin>();
	
	private Set<Team> teams = new HashSet<Team>();

问题补充：
上面的代码参数可能和下面的有一定的不一样，大家尝试着看吧
问题补充：
谢了，有点急。帮忙看一下
问题补充：

下面的代码很多，但是粗略看一下就行，不用一句一句的看 
/** 
* 根据条件查询 
*/ 
public List byStudent(String sno,String sname,String classid,int academyid){ 

Criteria critera = getSession().createCriteria(Student.class);//里面是一个class对象，而不是HQL 
if(sno!=null&&!sno.equals("")){//如果equals在前面的话，容易报 nullpoint 异常 
critera.add(Restrictions.like("sno", sno,MatchMode.ANYWHERE)); 
//如果是进行模糊查询的话，就要加一个参数，MatchMode.ANYWHERE ，否则就不能进行模糊查询 
} 
if(sname!=null&&!sname.equals("")){ 
critera.add(Restrictions.like("sname", sname,MatchMode.ANYWHERE)); 
} 
if(address!=null&&!address.equals("")){ 
critera.add(Restrictions.like("address", address,MatchMode.ANYWHERE)); 
} 
if(classid!=0){ 
critera.add(Restrictions.eq("classes.sid",new Integer(classid))); 
} 
if(academyid!=0){ 
critera.add(Restrictions.like("academyid",new Integer(academyid)); 
} 
return critera.list(); 
} 

问题补充：
全部的积分都压上了，帮一下吧
问题补充：

Criteria critera = getSession().createCriteria(Student.class);
if(classid!=0){    
        Criteria classes = critera.createCriteria("team");
        classes.add(Expression.eq("id", classid));
}
return critera.list();

你这是什么意思啊，没看明白，classes并没有和critera 关联上。能再详细一点么，加上点注释。
问题补充：
to yourgame 你的方法我尝试了，不行啊。还有别的办法没？谢了

critera.add(Restrictions.eq("team.academy.id",new Integer(academyid)));

问题补充：

javax.servlet.ServletException: org.hibernate.QueryException: could not resolve property: team.academy.id of: pojo.Student
	org.apache.struts.action.RequestProcessor.processException(RequestProcessor.java:545)
	org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:486)
	org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:274)
	org.apache.struts.action.ActionServlet.process(ActionServlet.java:1482)
	org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:525)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
	utils.EncodingFilter.doFilter(EncodingFilter.java:25)


root cause 

org.hibernate.QueryException: could not resolve property: team.academy.id of: pojo.Student
	org.hibernate.persister.entity.AbstractPropertyMapping.throwPropertyException(AbstractPropertyMapping.java:43)
	org.hibernate.persister.entity.AbstractPropertyMapping.toColumns(AbstractPropertyMapping.java:63)
	org.hibernate.persister.entity.BasicEntityPropertyMapping.toColumns(BasicEntityPropertyMapping.java:31)
	org.hibernate.persister.entity.AbstractEntityPersister.toColumns(AbstractEntityPersister.java:1257)
	org.hibernate.loader.criteria.CriteriaQueryTranslator.getColumns(CriteriaQueryTranslator.java:433)
	org.hibernate.loader.criteria.CriteriaQueryTranslator.getColumnsUsingProjection(CriteriaQueryTranslator.java:393)
	org.hibernate.criterion.SimpleExpression.toSqlString(SimpleExpression.java:45)
	org.hibernate.loader.criteria.CriteriaQueryTranslator.getWhereCondition(CriteriaQueryTranslator.java:333)
	org.hibernate.loader.criteria.CriteriaJoinWalker.<init>(CriteriaJoinWalker.java:82)
	org.hibernate.loader.criteria.CriteriaLoader.<init>(CriteriaLoader.java:67)
	org.hibernate.impl.SessionImpl.list(SessionImpl.java:1514)
	org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:283)
	dao.StudentDaoImpl.search(StudentDaoImpl.java:112)
	struts.action.StudentAction.search(StudentAction.java:93)
	sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	java.lang.reflect.Method.invoke(Method.java:597)
	org.apache.struts.actions.DispatchAction.dispatchMethod(DispatchAction.java:280)
	org.apache.struts.actions.DispatchAction.execute(DispatchAction.java:216)
	org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:484)
	org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:274)
	org.apache.struts.action.ActionServlet.process(ActionServlet.java:1482)
	org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:525)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
	utils.EncodingFilter.doFilter(EncodingFilter.java:25)

就是这个错误，我试过了，只要是属性（team.academy.i）与student中的属性不定应就会有这种错误，
问题补充：
这是StudentDaoImpl的代码，你看一看

	public List search(String id,String name,String academyid,String teamid){
		List students = null;
		Session sess = HibernateSessionFactory.getSession();
		Transaction tran = sess.beginTransaction();
		Criteria critera = sess.createCriteria(Student.class);
		if(!"".equals(id)&&id!=null){
			critera.add(Restrictions.eq("id",id));
		}
		if(!"".equals(name)&&name!=null){
			critera.add(Restrictions.eq("name",name));
		}
		if(!"".equals(teamid)&&teamid!=null){
			critera.add(Restrictions.eq("team.id",teamid));
		}
		if(!"".equals(academyid)&&academyid!=null){
			critera.add(Restrictions.eq("team.academy.id",academyid));
		}
		students = critera.list();
		tran.commit();
		sess.close();
		return students;
	}