Mybatis实现复杂查询（测试环境搭建）

文章目录

• 测试环境搭建
• • SQL
  • 第一步：建立实体类
  • • 建立Student类：
    • 建立Teacher类
  • 第二步：建立Mapper接口
  • • 建立StudentMapper接口
    • 建立TeacherMapper接口
  • 第三步：建立Mapperx.XML文件
  • • 建立TeacherMapper.xml文件
    • 建立StudentMapper.XML文件
  • 第四步：在核心配置文件中绑定注册我们的Mapper接口或者文件！
  • 第五步：测试类：查询是否能够成功
  • 文件结构：

---

测试环境搭建 SQL

• 学生通过tid关联老师；

create table `teacher`(
  `id` int(10) not null auto_increment,
  `name` varchar(20) default null,
  primary key(id)
)engine = innodb default charset utf8;

insert into teacher values (default,"lyh");

create table `student`(
  `id` int(10) not null,
  `name` varchar(20) default null,
  `tid` int(10) default null,
  primary key (`id`),
  key `fktid` (`tid`),
  constraint `fktid` foreign key (`tid`) references `teacher` (`id`)
)engine = innodb default charset utf8;

insert into student values (1,"mlb1",1);
insert into student values (default,"mlb2",1);
insert into student values (default,"mlb3",1);
insert into student values (default,"mlb4",1);
insert into student values (default,"mlb5",1);

第一步：建立实体类 建立Student类：

package org.pojo;

public class Student {
    private int id;
    private String name;

    //学生需要关联一个老师！
    private Teacher teacher;

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + ''' +
                ", 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 Teacher getTeacher() {
        return teacher;
    }

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

建立Teacher类

package org.pojo;

public class Teacher {
    private int id;
    private String name;

    @Override
    public String toString() {
        return "Teacher{" +
                "id=" + id +
                ", name='" + name + ''' +
                '}';
    }

    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;
    }

}

第二步：建立Mapper接口 建立StudentMapper接口

package org.dao;

public interface StudentMapper {

}

建立TeacherMapper接口

package org.dao;

import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import org.pojo.Teacher;

public interface TeacherMapper {
    @Select("select * from teacher where id = #{tid}")
    Teacher getTeacher(@Param("tid") int id);
}

第三步：建立Mapperx.XML文件 注意：在resource目录下 建立TeacherMapper.xml文件

建立StudentMapper.XML文件

第四步：在核心配置文件中绑定注册我们的Mapper接口或者文件！

第五步：测试类：查询是否能够成功

import org.apache.ibatis.session.SqlSession;
import org.dao.TeacherMapper;
import org.pojo.Teacher;
import org.utils.MybatisUtils;

public class MyTest {
    public static void main(String[] args) {
        SqlSession sqlSession = null;
        try{
            sqlSession = MybatisUtils.getSqlSession();
            TeacherMapper mapper = sqlSession.getMapper(TeacherMapper.class);
            Teacher teacher = mapper.getTeacher(1);
            System.out.println(teacher);
        }catch(Exception e){
            e.printStackTrace();
        }catch(Error e){
            e.printStackTrace();
        }finally{
            sqlSession.close();
        }
    }
}

文件结构：