今日目标:
- 一对多关联关系
- 多对多关联关系
本篇博客是在前四篇的基础上在进行进一步开发的
(四) | mybatis集成ehcache&&mybatis集成redis_m0_58525944的博客-CSDN博客 |
(三) | mybatis整合spring&&spring整合mybatis分页插件_m0_58525944的博客-CSDN博客 |
(二) | mybatis之动态sql&&模糊查询&&结果集处理&&mybatis分页&&特殊字符处理_m0_58525944的博客-CSDN博客 |
(一) | MyBatis入门(逆向生成&&增删改查案例)_m0_58525944的博客-CSDN博客 |
目录结构:
准备工作(使用逆向生成工具生成mapper及model)数据库中所需的数据库表,五张表
使用逆向生成工具生成mapper和model
利用order和orderitem两个表,来展示一对多的关联关系,一个订单中有多个订单项,多个订单项对应一个订单
1 建立两个vo类来存储一对多的关联属性(OrderVo:订单一方,OrderItemVo:订单项多方)
orderVo
package com.lgs.vo;
import com.lgs.model.Order;
import com.lgs.model.OrderItem;
import java.util.ArrayList;
import java.util.List;
//vo类是为了不破坏本身的类的封装性,跟数据库中的字段一一映射的
public class OrderVo extends Order {
// 一个订单中有多个订单项,所以用集合
private List orderItems = new ArrayList<>();
public List getOrderItems() {
return orderItems;
}
public void setOrderItems(List orderItems) {
this.orderItems = orderItems;
}
}
OrderItemVo
package com.lgs.vo;
import com.lgs.model.Order;
import com.lgs.model.OrderItem;
public class OrderItemVo extends OrderItem {
// 一个订单项对应一个订单
private Order order;
public Order getOrder() {
return order;
}
public void setOrder(Order order) {
this.order = order;
}
}
2 分别在OrderMapper.xml、OrderItemMapper.xml中添加映射关系配置 和 连表查,所以需要两边都要添加一个dao方法及配置sql语句
OrderMapper.xml
OrderItemMapper.xml
2 OrderMapper.java: 和 OrderItemMapper.java:的配置
OrderMapper.java:
OrderVo queryOrderVoByOrderId(@Param("orderId") Integer orderId);
OrderItemMapper.java:
OrderItemVo queryOrderItemVoByOrderItemId(@Param("orderItemId") Integer orderItemId);
3 建立One2ManyService.java类:
package com.lgs.service;
import com.lgs.vo.OrderItemVo;
import com.lgs.vo.OrderVo;
public interface One2ManyService {
//通过查询订单关联查询出对应的订单项信息
OrderVo queryOrderVoByOrderId(Integer orderId);
//查询订单项,关联查询出所属的订单
OrderItemVo queryOrderItemVoByOrderItemId(Integer OrderItemId);
}
4 建立One2ManyServiceImpl.java实现类:
package com.lgs.service.impl;
import com.lgs.mapper.OrderItemMapper;
import com.lgs.mapper.OrderMapper;
import com.lgs.service.One2ManyService;
import com.lgs.vo.OrderItemVo;
import com.lgs.vo.OrderVo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class One2ManyServiceImpl implements One2ManyService {
@Autowired
private OrderMapper orderMapper;
@Autowired
private OrderItemMapper orderItemMapper;
@Override
public OrderVo queryOrderVoByOrderId(Integer orderId) {
return orderMapper.queryOrderVoByOrderId(orderId);
}
@Override
public OrderItemVo queryOrderItemVoByOrderItemId(Integer OrderItemId) {
return orderItemMapper.queryOrderItemVoByOrderItemId(OrderItemId);
}
}
5 测试
package com.lgs.service.impl;
import com.lgs.model.OrderItem;
import com.lgs.service.One2ManyService;
import com.lgs.vo.OrderItemVo;
import com.lgs.vo.OrderVo;
import junit.framework.TestCase;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations={"classpath:applicationContext.xml"})
public class One2ManyServiceImplTest extends TestCase {
@Autowired
private One2ManyService one2ManyService;
@Test
public void queryOrderVoByOrderId() {
OrderVo orderVo = this.one2ManyService.queryOrderVoByOrderId(10);
System.out.println(orderVo);
for (OrderItem orderItem : orderVo.getOrderItems()) {
System.out.println(orderItem);
}
}
@Test
public void queryOrderItemVoByOrderItemId() {
OrderItemVo orderItemVo = this.one2ManyService.queryOrderItemVoByOrderItemId(49);
System.out.println(orderItemVo);
System.out.println(orderItemVo.getOrder());
}
}
通过查询订单关联查询出对应的订单项信息
查询订单项, 关联所属的订单
前面介绍了一对多的关系,那么接下来多对多的映射关系就简单多了,用两个connection配置
为展示多对多的关联关系,利用一本书对应多种类别,一种类别对应多本书的概念
1 建立两个vo类来存储多对多的关联属性(HBookVo:书籍,CategoryVo:书籍种类 都是多方,所以都用集合)
HBookVo.java:
package com.lgs.vo;
import com.lgs.model.Category;
import com.lgs.model.Hbook;
import java.util.ArrayList;
import java.util.List;
public class HbookVo extends Hbook {
private List categories = new ArrayList<>();
public List getCategories() {
return categories;
}
public void setCategories(List categories) {
this.categories = categories;
}
}
CategoryVo.java:
package com.lgs.vo;
import com.lgs.model.Category;
import com.lgs.model.Hbook;
import java.util.ArrayList;
import java.util.List;
public class CategoryVo extends Category {
private List hbooks = new ArrayList<>();
public List getHbooks() {
return hbooks;
}
public void setHbooks(List hbooks) {
this.hbooks = hbooks;
}
}
2 在HBookCategoryMapper.xml中添加映射关系配置 和 连表查,所以需要添加一个dao方法及配置sql语句
HBookCategoryMapper.xml(配置两个多对多和连表查的SQL):
3 HBookCategoryMapper.java(添加两个查询方法):
HbookVo queryByBookId(@Param("bookId") Integer bookId);
CategoryVo queryByCid(@Param("cid") Integer cid);
4 建立Many2ManyService.java类:
package com.lgs.service;
import com.lgs.vo.CategoryVo;
import com.lgs.vo.HbookVo;
import org.apache.ibatis.annotations.Param;
public interface Many2ManyService {
HbookVo queryByBookId(Integer bookId);
CategoryVo queryByCid(Integer cid);
}
5 建立Many2ManyServiceImpl.java实现类:
package com.lgs.service.impl;
import com.lgs.mapper.HbookCategoryMapper;
import com.lgs.service.Many2ManyService;
import com.lgs.vo.CategoryVo;
import com.lgs.vo.HbookVo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class Many2ManyServiceImpl implements Many2ManyService {
@Autowired
private HbookCategoryMapper hbookCategoryMapper;
@Override
public HbookVo queryByBookId(Integer bookId) {
return hbookCategoryMapper.queryByBookId(bookId);
}
@Override
public CategoryVo queryByCid(Integer cid) {
return hbookCategoryMapper.queryByCid(cid);
}
}
6 测试
package com.lgs.service.impl;
import com.lgs.model.Category;
import com.lgs.model.Hbook;
import com.lgs.service.Many2ManyService;
import com.lgs.vo.CategoryVo;
import com.lgs.vo.HbookVo;
import junit.framework.TestCase;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations={"classpath:applicationContext.xml"})
public class Many2ManyServiceImplTest extends TestCase {
@Autowired
private Many2ManyService many2ManyService;
@Test
public void queryByBookId() {
HbookVo hbookVo = many2ManyService.queryByBookId(8);
System.out.println(hbookVo);
for (Category category : hbookVo.getCategories()) {
System.out.println(category);
}
}
@Test
public void queryByCid() {
CategoryVo categoryVo = many2ManyService.queryByCid(8);
System.out.println(categoryVo);
for (Hbook hbook : categoryVo.getHbooks()) {
System.out.println(hbook);
}
}
}
根据书的id查看书有哪些类别
根据类别查询此书类别的书还有哪些
OK!到这就结束了,希望能帮到你!!!