本课程对应视频教程：http://edu.51cto.com/sd/3ec2c
1、高级查询
MyBatis作为一个ORM框架，也对sql的高级查询做了支持，这里以用户，订单，订单详情，商品为例讲解
案例说明：此案例的业务关系是用户、订单、订单详情、商品之间的关系、其中
一个订单只能属于一个人
一个订单可以有多个订单详情
一个订单详情中包含一个商品信息
他们的关系是：
订单和人是一对一的关系
订单和订单详情是一对多的关系
订单和商品是多对多的关系
1.1、数据模型分析
1.2、需求分析
一对一查询：查询订单，并且查询出下单人信息
一对多查询：查询订单，查询出下单人信息并且查询出订单详情
多对多查询：查询订单，查询出订单人信息并且查询出订单详情中的商品数据
1.3、一对一查询
1.3.1、方式一
将查询出来字段封装到一个新的类中，让这个类的属性包含所有查询出来的字段，
它的弊端在于，我的pojo类会急剧增加
先定义一个实体类
package cn.org.kingdom.pojo;
public class OrderUser extends User {
private int oid;
private int userId;
private String orderNum;
public int getOid() {
return oid;
}
public void setOid(int oid) {
this.oid = oid;
}
public int getUserId() {
return userId;
}
public void setUserId(int userId) {
this.userId = userId;
}
public String getOrderNum() {
return orderNum;
}
public void setOrderNum(String orderNum) {
this.orderNum = orderNum;
}
@Override
public String toString() {
return "OrderUser [oid=" + oid + ", userId=" + userId + ", orderNum="
+ orderNum + ", userid=" + userid + ", userName=" + userName
+ ", pwd=" + pwd + ", age=" + age + ", sex=" + sex
+ ", birthday=" + birthday + "]";
}
}定义数据接口
public List one2one(@Param("orderNum")String orderNum); 配置mapper.xml文件（OrderMapper.xml）
测试类
package cn.org.kingdom.test;
import java.io.InputStream;
import java.util.List;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import cn.org.kingdom.mapper.OrderMapper;
import cn.org.kingdom.pojo.OrderUser;
import cn.org.kingdom.pojo.User;
public class MyBatisTest03 {
SqlSessionFactory sqlSessionFactory = null ;
SqlSession sqlSession = null ;
OrderMapper orderMapper = null ;
@Before
public void setUp() throws Exception {
//加载资源
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
sqlSession = sqlSessionFactory.openSession();
orderMapper = sqlSession.getMapper(OrderMapper.class);
}
@After
public void tearDown() throws Exception {
//关闭
sqlSession.close();
}
@Test
public void testone2one()throws Exception{
List list = orderMapper.one2one("20180810001");
for (OrderUser u : list) {
System.out.println(u);
}
}
} 生成的日志
DEBUG - Opening JDBC Connection
DEBUG - Created connection 665964512.
DEBUG - Setting autocommit to false on JDBC Connection [oracle.jdbc.driver.T4CConnection@27b1cfe0]
DEBUG - ==> Preparing: select tb_user.*,tb_order.* from tb_user,tb_order where tb_user.userid = tb_order.user_id and order_number=?
DEBUG - ==> Parameters: 20180810001(String)
DEBUG - <== Total: 1
OrderUser [oid=1, userId=0, orderNumber=20180810001, userid=2, userName=阿柯, pwd=123456, age=10, sex=女, birthday=Tue Aug 14 13:45:34 CST 2018]
DEBUG - Resetting autocommit to true on JDBC Connection [oracle.jdbc.driver.T4CConnection@27b1cfe0]
DEBUG - Closing JDBC Connection [oracle.jdbc.driver.T4CConnection@27b1cfe0]
DEBUG - Returned connection 665964512 to pool.1.3.2、采用面向对象的思维
让一个类持有另外一个类的属性
定义一个Order类
package cn.org.kingdom.pojo;
import java.io.Serializable;
public class Order implements Serializable {
private int oid;
private int userId;
private String orderNumber;
private User user ;
public int getOid() {
return oid;
}
public void setOid(int oid) {
this.oid = oid;
}
public int getUserId() {
return userId;
}
public void setUserId(int userId) {
this.userId = userId;
}
public String getOrderNumber() {
return orderNumber;
}
public void setOrderNumber(String orderNumber) {
this.orderNumber = orderNumber;
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
@Override
public String toString() {
return "Order [oid=" + oid + ", userId=" + userId + ", orderNumber="
+ orderNumber + ", user=" + user + "]";
}
}mapper.xml文件
测试类
@Test
public void testone2one2()throws Exception{
List list = orderMapper.one2one2("20180810001");
for (Order u : list) {
System.out.println(u);
}
} 日志：
DEBUG - ==> Preparing: select tb_user.*,tb_order.* from tb_user,tb_order where tb_user.userid = tb_order.user_id and order_number=?
DEBUG - ==> Parameters: 20180810001(String)
DEBUG - <== Total: 1
Order [oid=1, userId=2, orderNumber=20180810001, user=User [userid=2, userName=阿柯, pwd=123456, age=10, sex=女, birthday=Tue Aug 14 13:45:34 CST 2018]]
DEBUG - Resetting autocommit to true on JDBC Connection [oracle.jdbc.driver.T4CConnection@5bad7476]
DEBUG - Closing JDBC Connection [oracle.jdbc.driver.T4CConnection@5bad7476]
DEBUG - Returned connection 1538094198 to pool.1.4、一对多查询
一对多查询：查询订单，查询出下单人信息并且查询出订单详情
sql
select tb_user.*,tb_order.*,tb_orderdetail.*
from tb_user,tb_order,tb_orderdetail
where tb_user.userid = tb_order.user_id
and tb_order.oid = tb_orderdetail.order_id
and order_number ='20180810001'创建pojo类
package cn.org.kingdom.pojo;
import java.io.Serializable;
public class Detail implements Serializable{
private int detailId;
private int orderId;
private int productId;
private double price;
private String status;
public Detail() {
super();
}
public int getDetailId() {
return detailId;
}
public void setDetailId(int detailId) {
this.detailId = detailId;
}
public int getOrderId() {
return orderId;
}
public void setOrderId(int orderId) {
this.orderId = orderId;
}
public int getProductId() {
return productId;
}
public void setProductId(int productId) {
this.productId = productId;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
public String getStatus() {
return status;
}
public void setStatus(String status) {
this.status = status;
}
@Override
public String toString() {
return "Detail [detailId=" + detailId + ", orderId=" + orderId
+ ", productId=" + productId + ", price=" + price + ", status="
+ status + "]";
}
}
然后在Order中加入多的一方的引用
private List details ;
public List getDetails() {
return details;
}
public void setDetails(List details) {
this.details = details;
} mapper.xml文件
测试类
public void testone2many()throws Exception{
List list = orderMapper.one2many("20180810001");
for (Order u : list) {
System.out.println(u);
}
} 日志信息
DEBUG - Cache Hit Ratio [cn.org.kingdom.mapper.OrderMapper]: 0.0
DEBUG - Opening JDBC Connection
DEBUG - Created connection 15932635.
DEBUG - Setting autocommit to false on JDBC Connection [oracle.jdbc.driver.T4CConnection@f31cdb]
DEBUG - ==> Preparing: select tb_user.*,tb_order.*,tb_orderdetail.* from tb_user,tb_order,tb_orderdetail where tb_user.userid = tb_order.user_id and tb_order.oid = tb_orderdetail.order_id and order_number =?
DEBUG - ==> Parameters: 20180810001(String)
DEBUG - <== Total: 2
Order [oid=1, userId=2, orderNumber=20180810001, user=User [userid=2, userName=阿柯, pwd=123456, age=10, sex=女, birthday=Tue Aug 14 13:45:34 CST 2018], details=[Detail [detailId=1, orderId=1, productId=1, price=8888.0, status=1], Detail [detailId=2, orderId=1, productId=2, price=188.0, status=1]]]
DEBUG - Resetting autocommit to true on JDBC Connection [oracle.jdbc.driver.T4CConnection@f31cdb]
DEBUG - Closing JDBC Connection [oracle.jdbc.driver.T4CConnection@f31cdb]
DEBUG - Returned connection 15932635 to pool.1.5、多对多
多对多查询：查询订单，查询出订单人信息并且查询出订单详情中的商品数据
sql语句分析
select tb_user.*,tb_order.*,tb_orderdetail.*,tb_product.*
from tb_user,tb_order,tb_orderdetail,tb_product
where tb_user.userid = tb_order.user_id
and tb_order.oid = tb_orderdetail.order_id
and tb_orderdetail.product_id = tb_product.pid
and order_number ='20180810001'接口方法定义
public List many2many(@Param("orderNum")String orderNum); 创建一个pojo类(Product)
package cn.org.kingdom.pojo;
public class Product implements Serializable {
private int pid;
private String pname ;
private double price ;
private String proDetail;
public int getPid() {
return pid;
}
public void setPid(int pid) {
this.pid = pid;
}
public String getPname() {
return pname;
}
public void setPname(String pname) {
this.pname = pname;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
public String getProDetail() {
return proDetail;
}
public void setProDetail(String proDetail) {
this.proDetail = proDetail;
}
@Override
public String toString() {
return "Product [pid=" + pid + ", pname=" + pname + ", price=" + price
+ ", proDetail=" + proDetail + "]";
}
}在detail类中加入一个Product类的引用
private Product product;
public Product getProduct() {
return product;
}
public void setProduct(Product product) {
this.product = product;
}mapper.xml文件
测试类
@Test
public void testmany2many()throws Exception{
List list = orderMapper.many2many("20180810001");
for (Order u : list) {
System.out.println(u);
}
} 日志
DEBUG - Opening JDBC Connection
DEBUG - Created connection 462907404.
DEBUG - Setting autocommit to false on JDBC Connection [oracle.jdbc.driver.T4CConnection@1b97680c]
DEBUG - ==> Preparing: select tb_user.*,tb_order.*,tb_orderdetail.*,tb_product.* from tb_user,tb_order,tb_orderdetail,tb_product where tb_user.userid = tb_order.user_id and tb_order.oid = tb_orderdetail.order_id and tb_orderdetail.product_id = tb_product.pid and order_number =?
DEBUG - ==> Parameters: 20180810001(String)
DEBUG - <== Total: 2
Order [oid=1, userId=2, orderNumber=20180810001, user=User [userid=2, userName=阿柯, pwd=123456, age=10, sex=女, birthday=Tue Aug 14 13:45:34 CST 2018], details=[Detail [detailId=1, orderId=1, productId=1, price=8888.0, status=1, product=Product [pid=1, pname=iphone8, price=8888.0, proDetail=苹果公司最新产品]], Detail [detailId=2, orderId=1, productId=2, price=188.0, status=1, product=Product [pid=2, pname=冰峰战神, price=188.0, proDetail=关羽骚气皮肤]]]]
DEBUG - Resetting autocommit to true on JDBC Connection [oracle.jdbc.driver.T4CConnection@1b97680c]
DEBUG - Closing JDBC Connection [oracle.jdbc.driver.T4CConnection@1b97680c]
DEBUG - Returned connection 462907404 to pool.
1.6、resultMap的继承
resultMap元素可以通过继承机制来减少冗余
然后测试，运行ok