mappedBy reference an unknown target entity property错误

[lzw]

package com.aj.footprint.model.po;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.Table;


/**
 * 菜单
 * 
 * 
 */
@Entity
@Table(name = "F_MENU")
public class TMenu implements Serializable{
	private static final long serialVersionUID = 1L;

	// Constructors

		/** default constructor */
		public TMenu() {
		}

		/** minimal constructor */
		public TMenu(String mid, String fname) {
			this.mid = mid;
			this.fname = fname;
		}

		/** full constructor */
		public TMenu(String mid, TMenu tmenu, String icon, String fname, Integer seq, String furl, Set<TMenu> tmenus,String roleids) {
			this.mid = mid;
			this.tmenu = tmenu;
			this.icon = icon;
			this.fname = fname;
			this.seq = seq;
			this.furl = furl;
			this.tmenus = tmenus;
			this.roleids=roleids;
		}
		
	/**
	 * ID
	 */	
	private String mid;
	
	/**
	 * 图标
	 */
	private String icon;
	
	/**
	 * 名称
	 */
	private String fname;
	
	/**
	 * 编号
	 */
	private Integer seq;
	
	/**
	 * url
	 */
	private String furl;
	
	/**
	 * 角色
	 */
	private String roleids;
	

	private TMenu tmenu;
	
	/**
	 * 下级列表
	 */
	private Set<TMenu> tmenus = new HashSet<TMenu>(0);

	@Id
	@Column(name = "ID" , length = 10)
	@GeneratedValue(strategy = GenerationType.AUTO)
	public String getMid() {
		return mid;
	}

	public void setMid(String mid) {
		this.mid = mid;
	}

	@Column(name = "ICON" , length = 50)
	public String getIcon() {
		return icon;
	}

	public void setIcon(String icon) {
		this.icon = icon;
	}

	@Column(name = "FNAME" , length = 50)
	public String getFname() {
		return fname;
	}

	public void setFname(String fname) {
		this.fname = fname;
	}

	@Column(name = "SEQ")
	public Integer getSeq() {
		return seq;
	}

	public void setSeq(Integer seq) {
		this.seq = seq;
	}

	@Column(name = "FURL" , length = 200)
	public String getFurl() {
		return furl;
	}

	public void setFurl(String furl) {
		this.furl = furl;
	}

/*	@Column(name = "BELONGTO" , length = 10)
	public String getBelongto() {
		return belongto;
	}

	public void setBelongto(String belongto) {
		this.belongto = belongto;
	}*/

	@Column(name = "ROLEIDS" , length = 20)
	public String getRoleids() {
		return roleids;
	}

	public void setRoleids(String roleids) {
		this.roleids = roleids;
	}

	@ManyToOne(fetch = FetchType.LAZY)
	@JoinColumn(name = "BELONGTO")
	public TMenu getTMenu() {
		return tmenu;
	}

	public void setTMenu(TMenu tmenu) {
		this.tmenu = tmenu;
	}

	@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "tmenu")
	public Set<TMenu> getTmenus() {
		return tmenus;
	}

	public void setTmenus(Set<TMenu> tmenus) {
		this.tmenus = tmenus;
	}
	
	

}

这是po类，为什么一直报:
Invocation of init method failed; nested exception is org.hibernate.AnnotationException: mappedBy reference an unknown target entity property: com.aj.footprint.model.po.TMenu.tmenu in com.aj.footprint.model.po.TMenu.tmenus