package com.test.ioc;

import org.nutz.dao.entity.annotation.Column;
import org.nutz.dao.entity.annotation.Id;
import org.nutz.dao.entity.annotation.Table;

@Table("tb_idcard")
public class IdCard {
	@Id
	private long id;
	@Column
	private String carNo;
	private User user;

	public long getId() {
		return id;
	}

	public void setId(long id) {
		this.id = id;
	}

	public String getCarNo() {
		return carNo;
	}

	public void setCarNo(String carNo) {
		this.carNo = carNo;
	}

	public User getUser() {
		return user;
	}

	public void setUser(User user) {
		this.user = user;
	}

}

package com.test.ioc;

import org.nutz.dao.entity.annotation.Column;
import org.nutz.dao.entity.annotation.Id;
import org.nutz.dao.entity.annotation.Name;
import org.nutz.dao.entity.annotation.One;
import org.nutz.dao.entity.annotation.Table;

@Table("tb_user1")
public class User {
	@Id
	private long id;
	@Name
	@Column
	private String name;
	@One(field = "cardId")
	private IdCard a;
	@Column
	private long cardId;

	public long getId() {
		return id;
	}

	public void setId(long id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}


	public IdCard getA() {
		return a;
	}

	public void setA(IdCard a) {
		this.a = a;
	}

	public long getCardId() {
		return cardId;
	}

	public void setCardId(long cardId) {
		this.cardId = cardId;
	}

}

貌似上面这样写是单向的 从user可以找到idcard，从idcard不能找到user啊
IdCard idCard = dao.fetch(IdCard.class, 1);
dao.fetchLinks(idCard, "user");
System.out.println(idCard.getUser().getName());这样写报空指针异常。。，用user是可以的！！，请问怎么解决这种双向 我在private User user;加上one(field="cardId")的时候就报错了！！