mybatis复杂一对多映射配置示例

1、先看下各个POJO类：

package com.js.mybatis.po;
/**
 * 用户po类
 * 单独使用mybatis时，mapper.xml中的OGNL表达式通过getter()方法来读取pojo类的属性值
 * 当mybatis和spring整合时，spring通过反射来读取pojo类的属性值
 */
import java.util.Date;
import java.util.List;

public class User {
	@Override
	public String toString() {
		return "User [id=" + id + ", username=" + username + ", sex=" + sex
				+ ", birthday=" + birthday + ", address=" + address + "]";
	}
	private int id;
	private String username;
	private String sex;
//	多个订单
	private List<Orders> orders;
	public List<Orders> getOrders() {
		return orders;
	}
	public void setOrders(List<Orders> orders) {
		this.orders = orders;
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
	public Date getBirthday() {
		return birthday;
	}
	public void setBirthday(Date birthday) {
		this.birthday = birthday;
	}
	public String getAddress() {
		return address;
	}
	public void setAddress(String address) {
		this.address = address;
	}
	private Date birthday;
	private String address;
}

package com.js.mybatis.po;

import java.io.Serializable;
import java.util.Date;
import java.util.List;

public class Orders implements Serializable {
    /**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	private Integer id;

    private Integer userId;

    private String number;

    private Date createtime;

    private String note;
    
    /**
     * 关联的用户信息
     */
    private User user;
    /**
     * 关联订单信息（多个）
     * 使用集合
     * @return
     */
    private List<Orderdetail> orderdetails;
   
    public List<Orderdetail> getOrderdetails() {
		return orderdetails;
	}

	public void setOrderdetails(List<Orderdetail> orderdetails) {
		this.orderdetails = orderdetails;
	}

	public User getUser() {
		return user;
	}

	@Override
	public String toString() {
		return "Orders [id=" + id + ", userId=" + userId + ", number=" + number
				+ ", createtime=" + createtime + ", note=" + note + ", user="
				+ user + "]";
	}

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

	public Integer getId() {
        return id;
    }

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

    public Integer getUserId() {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }

    public String getNumber() {
        return number;
    }

    public void setNumber(String number) {
        this.number = number == null ? null : number.trim();
    }

    public Date getCreatetime() {
        return createtime;
    }

    public void setCreatetime(Date createtime) {
        this.createtime = createtime;
    }

    public String getNote() {
        return note;
    }

    public void setNote(String note) {
        this.note = note == null ? null : note.trim();
    }   
    
}

package com.js.mybatis.po;

import java.io.Serializable;

public class Orderdetail implements Serializable {
    /**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	private Integer id;

    private Integer ordersId;

    private Integer itemsId;

    private Integer itemsNum;
    
    //商品信息
    private Items items;

    public Integer getId() {
        return id;
    }

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

    public Integer getOrdersId() {
        return ordersId;
    }

    public void setOrdersId(Integer ordersId) {
        this.ordersId = ordersId;
    }

    public Integer getItemsId() {
        return itemsId;
    }

    public void setItemsId(Integer itemsId) {
        this.itemsId = itemsId;
    }

    public Integer getItemsNum() {
        return itemsNum;
    }

    public void setItemsNum(Integer itemsNum) {
        this.itemsNum = itemsNum;
    }
    
    

	public Items getItems() {
		return items;
	}

	public void setItems(Items items) {
		this.items = items;
	}

	@Override
	public String toString() {
		return "Orderdetail [id=" + id + ", ordersId=" + ordersId
				+ ", itemsId=" + itemsId + ", itemsNum=" + itemsNum + "]";
	}
    
}

package com.js.mybatis.po;

import java.io.Serializable;
import java.util.Date;

public class Items implements Serializable {
    /**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	private Integer id;

    private String name;

    private Float price;

    private String pic;

    private Date createtime;

    private String detail;

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name == null ? null : name.trim();
    }

    public Float getPrice() {
        return price;
    }

    public void setPrice(Float price) {
        this.price = price;
    }

    public String getPic() {
        return pic;
    }

    public void setPic(String pic) {
        this.pic = pic == null ? null : pic.trim();
    }

    public Date getCreatetime() {
        return createtime;
    }

    public void setCreatetime(Date createtime) {
        this.createtime = createtime;
    }

    public String getDetail() {
        return detail;
    }

    public void setDetail(String detail) {
        this.detail = detail == null ? null : detail.trim();
    }

	@Override
	public String toString() {
		return "Items [id=" + id + ", name=" + name + ", price=" + price
				+ ", pic=" + pic + ", createtime=" + createtime + ", detail="
				+ detail + "]";
	}
    
}

关系：User-Order 一对多

Order-OrderDetail 一对多

OrderDetai-Items 一对一

2、mapper配置：

<!-- 一对多查询用户、订单、订单明细、商品信息 -->
	 <resultMap type="user" id="userOrderDetailResultMap">
	 <!-- 用户信息 -->
	 <id column="user_id" property="id"/>
	 <result column="username" property="username"/>
	 <result column="sex" property="sex"/>
	 <!-- 订单信息 -->
	 <collection property="orders" javaType="orders">
	 	<id column="id" property="id"/>
	 	<result column="user_id" property="userId"/>
	 	<result column="number" property="number"/>
	 	<result column="createtime" property="createtime"/>
	 	<result column="note" property="note"/>
	 	<!-- 订单明细 -->
	 	<collection property="orderdetails" javaType="orderdetail">
	 		<id column="orderdetail_id" property="id"/>
	 		<result column="items_num" property="itemsNum"/>
	 		<result column="items_id" property="itemsId"/>
	 		<!-- 商品信息 -->
	 		<association property="items" javaType="items">
	 			<id column="items_id" property="id"/>
	 			<result column="items_name" property="name"/>
	 			<result column="items_detail" property="detail"/>  
	 		</association>
	 	</collection>
	 </collection>
	 </resultMap>
	 <select id="findUserOrderDetail" resultMap="userOrderDetailResultMap">
	 	SELECT 
  orders.*,
  user.username,
  user.sex,
  orderdetail.id orderdetail_id,
  orderdetail.items_num,
  orderdetail.items_id,
  items.name items_name,
  items.detail items_detail 
FROM
  orders,
  USER,
  orderdetail,
  items 
WHERE orders.user_id = user.id 
  AND orders.id = orderdetail.orders_id 
  AND items.id = orderdetail.items_id 
	 </select>