基于mybatis的的单表多表查询resultMap用法

对应的老师实体类：

class Teacher{

public class Teacher {
private int id1;
private String name1;

   public int getId() {
       return id;
   }

   public void setId(int id) {
       this.id = id;
   }

   public String getName() {
       return name;
   }

   public void setName(String name) {
       this.name = name;
   }
}

}

学生实体类：

public class Student {
   private int id;
   private String name;
   private int age;
   private Teacher teacher;

private int tid;

   public Teacher getTeacher() {
       return teacher;
   }

   public void setTeacher(Teacher teacher) {
       this.teacher = teacher;
   }

   public int getId() {
       return id;
   }

   public void setId(int id) {
       this.id = id;
   }

   public String getName() {
       return name;
   }

   public void setName(String name) {
       this.name = name;
   }

   public int getAge() {
       return age;
   }

   public void setAge(int age) {
       this.age = age;
   }

   public int getTid() {
       return tid;
   }

   public void setTid(int tid) {
       this.tid = tid;
   }
}

对应的mybatis中teacherMapper.xml的写法：

<?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="a.b">

</resultMap>
   <select id="selAll" resultMap="mymap">
   select * from teacher
   </select>

select * from teacher where id=#{0}

</select>

</mapper>

测试时，与使用autoMappering一样。

测试：

public class Test {
   public static void main(String[] args) throws IOException {
       InputStream is = (InputStream) Resources.getResourceAsStream("mybatis.xml");
       SqlSessionFactory factory = (SqlSessionFactory) new SqlSessionFactoryBuilder().build(is);
       SqlSession session=factory.openSession();
      session.selectList("a.b.selAll");
       session.close();

使用resultMap实现关联单个对象（N+1方式查询）

n+1方式查询：先查出某个表的全部信息，根据这个表的信息查询另一个表的信息。

对应的mybatis中studentMapper.xml的写法：

<?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="c.d">

</resultMap>
   <select id="selAll" resultMap="stumap">
   select * from student
   </select>
</mapper>