标签：之一 org id ibatis apache import MyBatis 注解 public
MyBatis注解之一对多
准备Mapper
- CategoryMapper接口中追加listOneToMany方法：
@Select(" select * from category_ ")
@Results({
@Result(property = "id", column = "id"),
@Result(property = "products", javaType = List.class, column = "id", many = @Many(select = "com.nyf.mappers.ProductMapper.listByCategory") )
})
public List<Category> listOneToMany();
点击查看完整CategoryMapper
package com.nyf.mappers;
import java.util.List;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;
import org.apache.ibatis.annotations.Many;
import com.nyf.pojo.Category;
public interface CategoryMapper {
@Insert(" insert into category_ ( name ) values (#{name}) ")
public int add(Category category);
@Delete(" delete from category_ where id= #{id} ")
public void delete(int id);
@Select("select * from category_ where id= #{id} ")
public Category get(int id);
@Update("update category_ set name=#{name} where id=#{id} ")
public int update(Category category);
@Select(" select * from category_ ")
public List list();
@Select(" select * from category_ ")
@Results({
@Result(property = "id", column = "id"),
@Result(property = "products", javaType = List.class, column = "id", many = @Many(select = "com.nyf.mappers.ProductMapper.listByCategory") )
})
public List listOneToMany();
}
- 新建ProductMapper接口，添加listByCategory方法：
@Select(" select * from product_ where cid = #{cid}")
public List<Product> listByCategory(int cid);
点击查看完整ProductMapper
package com.nyf.mappers;
import java.util.List;
import org.apache.ibatis.annotations.Select;
import com.nyf.pojo.Product;
public interface ProductMapper {
@Select(" select * from product_ where cid = #{cid}")
public List listByCategory(int cid);
}
修改配置文件
mybatis-config.xml中添加ProductMapper的映射：
<mapper class="com.nyf.mappers.ProductMapper"/>
点击查看完整mybatis-config.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<plugins>
<plugin interceptor="com.github.pagehelper.PageInterceptor">
</plugin>
</plugins>
<!-- environments配置要连接的数据库 -->
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/nyf?characterEncoding=UTF-8"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
</environments>
<!-- mappers,指明实体类对应的配置文件 -->
<mappers>
<mapper class="com.nyf.mappers.CategoryMapper"/>
<mapper class="com.nyf.mappers.ProductMapper"/>
<mapper class="com.nyf.mappers.OrderItemMapper"/>
<mapper class="com.nyf.mappers.OrderMapper"/>
</mappers>
</configuration>
编写测试类OneToMany
点击查看完整OneToMany
package com.nyf.tests;
import java.io.IOException;
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 com.nyf.mappers.CategoryMapper;
import com.nyf.pojo.Category;
import com.nyf.pojo.Product;
public class OneToMany {
public static void main(String[] args) throws IOException {
String resource = "com/nyf/config/mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession session = sqlSessionFactory.openSession();
CategoryMapper mapper = session.getMapper(CategoryMapper.class);
listAll(mapper);
session.commit();
session.close();
}
private static void listAll(CategoryMapper mapper) {
List cs = mapper.listOneToMany();
for (Category c : cs) {
System.out.println(c.getName());
List ps = c.getProducts();
for (Product p : ps) {
System.out.println("\t"+p.getName());
}
}
}
}
结果验证
正确结果应该如下所示：
category1
product a
product b
product c
category
product x
product y
product zzzzzz
标签：之一,org,id,ibatis,apache,import,MyBatis,注解,public 来源： https://www.cnblogs.com/nyfblog/p/13874449.html
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