Hibernate no session 错误

org.hibernate.LazyInitializationException: could not initialize proxy - no Session

//员工类
public class Employee implements java.io.Serializable {
	private Integer empno;
	private Department department;
	private String ename;
	private String job;
	private Date hiredate;
	private Double sal;
	private String pictureuri;
	private Double maxsal;
	private Double minsal;
}
//部门类
public class Department implements java.io.Serializable {
	private Integer deptno;
	private String dname;
	private Set employees = new HashSet(0);
}

//查询所有员工
public List<Employee>findAll(){
		List <Employee> empList=getSession().createCriteria(Employee.class).createCriteria("department").list();
//后面一定得加上createCriteria("department")这个条件，Hibernate才会去关联的部门表中查询员工的部门信息！！！不加的话，当你遍历empList集合输出员工部门时就会报上边所列错误，因为员工表中存放的只是一个部门ID外键，Hibernate不会主动去查询！切记！！！
		return empList;
	}