JavaEE_Mybatis_SpringMVC_Mybatis_lesson12_一对多关联映射（ResultMap）

项目代码

http://pan.baidu.com/s/1c01BLvi

主要文件

1.Mapper.xml

2.Mapper.java

3.pojo类

1.Mapper.xml

注意事项：

1.若有大量的重复代码，resultMap可以使用继承的方式，示例

2.assocation与collection的区别
assocation: 将关联查询到的记录映射到pojo中，与 javaType 配合使用

collection: 将关联查询到的多条记录映射到集合对象中，与 ofType 配合使用

3.id 中的 columun

column="xxx"  xxx对应数据库查询出来的字段

注意id 中的column需要各不相同, 可以采用取别名的方式

示例

		SELECT 
			orders.*, 
			user.username, 
			user.sex, 
			user.address,
			orderdetail.id orderdetail_id,
			orderdetail.items_id,
			orderdetail.items_num,
			orderdetail.orders_id
		FROM user,
			 orders, 
			 orderdetail
		WHERE orders.user_id = user.id AND orderdetail.orders_id = orders.id
	

2.Mapper.java

package cn.itcast.mybatis.mapper;

import java.util.List;

import cn.itcast.mybatis.po.Orders;
import cn.itcast.mybatis.po.OrdersCustom;

public interface UserCustomMapper {
	// 根据订单查询用户信息
	// 主表：Orders
	// 从表：User
	List findOrderUser() throws Exception;

	// 利用ResultMap进行关联映射
	List findOrderUserResultMap() throws Exception;

	// 利用ResultMap进行关联映射
	List findOrdersAndOrderDetailMap() throws Exception;
}

3.pojo类

package cn.itcast.mybatis.po;

import java.util.Date;
import java.util.List;

public class Orders {
    private Integer id;

    private Integer userId;

    private String number;

    private Date createtime;

    private String note;
    
    //用户信息
    private User user;
    
    //订单明细
    private List orderdetails;

    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();
    }

	public User getUser() {
		return user;
	}

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

	public List getOrderdetails() {
		return orderdetails;
	}

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

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

package cn.itcast.mybatis.po;

import java.util.Date;

//hibernate字段名和属性名相对应
public class User {
	@Override
	public String toString() {
		return "User [id=" + id + ", username=" + username + ", birthday="
				+ birthday + ", sex=" + sex + ", address=" + address + "]";
	}

	private int id;
	private String username;
	private Date birthday;
	private String sex;
	private String address;

	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 Date getBirthday() {
		return birthday;
	}

	public void setBirthday(Date birthday) {
		this.birthday = birthday;
	}

	public String getSex() {
		return sex;
	}

	public void setSex(String sex) {
		this.sex = sex;
	}

	public String getAddress() {
		return address;
	}

	public void setAddress(String address) {
		this.address = address;
	}

}

package cn.itcast.mybatis.po;

public class Orderdetail {
    private Integer id;

    private Integer ordersId;

    private Integer itemsId;

    private Integer itemsNum;

    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;
    }

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