create table book
(
 bid int primary key auto_increment,
 bname varchar(20)   
);

create table category
(
 cid int primary key auto_increment,
 cname varchar(20)
);

create table middle
(
 m_bid int,
 m_cid int,
 constraint fk_bid foreign key(m_bid) references book(bid),
 constraint fk_cid foreign key(m_cid) references category(cid)
);

insert into category values (default,'java');
insert into category values (default,'c++');
insert into category values (default,'mysql');
insert into book values (default,'SQL技术');
insert into book values (default,'SSM+MySQL详解');
insert into book values (default,'C++和java对比');
insert into middle values (1,3);
insert into middle values (2,1);
insert into middle values (2,3);
insert into middle values (3,2);
insert into middle values (3,1);

public class Book {
 private Integer bid;
 private String bname;
 public Integer getBid() {
 return bid;
 }
 public void setBid(Integer bid) {
 this.bid = bid;
 }
 public String getBname() {
 return bname;
 }
 public void setBname(String bname) {
 this.bname = bname == null ? null : bname.trim();
 }
}

public class Book {
 private Integer bid;
 private String bname;
 private List<Category> categories;
 public Integer getBid() {
 return bid;
 }
 public void setBid(Integer bid) {
 this.bid = bid;
 }
 public String getBname() {
 return bname;
 }
 public void setBname(String bname) {
 this.bname = bname == null ? null : bname.trim();
 }
 public List<Category> getCategories() {
 return categories;
 }
 public void setCategories(List<Category> categories) {
 this.categories = categories;
 }
}

select 
 * 
from 
 book b
　　inner join 
 　　 middle m
　　on
 　　 b.bid=m.m_bid
　　inner join
 　　 category c
　　on
　　 m.m_cid=c.cid

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.mybatis.dao.BookMapper" >
 <select id="queryAll"> 
 </select>
</mapper>

public interface BookMapper {
 List<Book> queryAll();
}

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.mybatis.dao.BookMapper" > 
 <resultMap type="com.mybatis.entity.Book" id="bookMap">
 <id property="bid" column="bid" />
 <result property="bname" column="bname" /> 
 <collection property="categories" ofType="com.mybatis.entity.Category">
 <id property="cid" column="cid" />
 <result property="cname" column="cname" /> 
 </collection>
 </resultMap>
 <select id="queryAll" resultMap="bookMap">
 select 
 * 
 from 
 book b
 inner join 
 middle m
 on
 b.bid=m.m_bid
 inner join
 category c
 on
 m.m_cid=c.cid
 </select>
</mapper>

public class MyMain {
 public static void main(String[] args) throws IOException {
 String resource = "mybatis-config.xml";
 Reader reader = Resources.getResourceAsReader(resource);
 SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(reader);
 SqlSession session = factory.openSession();
 BookMapper bookMapper = session.getMapper(BookMapper.class);
 for (Book book : bookMapper.queryAll()) {
 System.out.print("["+book.getBname()+"]");
 for(Category category :book.getCategories()){
 System.out.print(category.getCname()+"\t");
 }
 System.out.println("\n");
 }
 }
}