复杂查询环境搭建

• 关联和集合
• SQL
• 文件配置
• • 两个实体类接口
  • 实体类
  • 连接SqlSession
  • 资源文件
  • 测试类
  • pom配置
  • 运行结果

多个学生对应一个老师
对于学生而言，关联多个学生，关联一个老师
对于老师而已言，一个老师有多个学生（集合）

关联和集合

SQL

CREATE TABLE `teacher` (
                           `id` INT(10) NOT NULL,
                           `name` VARCHAR(30) DEFAULT NULL,
                           PRIMARY KEY (`id`)
) ;
INSERT INTO teacher(`id`, `name`) VALUES (1, '秦老师');
CREATE TABLE `student` (
                           `id` INT(10) NOT NULL,
                           `name` VARCHAR(30) DEFAULT NULL,
                           `tid` INT(10) DEFAULT NULL,
                           PRIMARY KEY (`id`),
                           KEY `fktid` (`tid`),
                           CONSTRAINT `fktid` FOREIGN KEY (`tid`) REFERENCES `teacher` (`id`)
);
INSERT INTO `student` (`id`, `name`, `tid`) VALUES ('1', '小明', '1');
INSERT INTO `student` (`id`, `name`, `tid`) VALUES ('2', '小红', '1');
INSERT INTO `student` (`id`, `name`, `tid`) VALUES ('3', '小张', '1');
INSERT INTO `student` (`id`, `name`, `tid`) VALUES ('4', '小李', '1');
INSERT INTO `student` (`id`, `name`, `tid`) VALUES ('5', '小王', '1');

文件配置

两个实体类接口

package com.my.dao;

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

public interface TeacherMapper {

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

package com.my.dao;

public interface StudentMapper {
}

实体类

package com.my.pojo;

import lombok.Data;

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

    //学生关联老师
    private Teacher teacher;
}

package com.my.pojo;

import lombok.Data;

@Data
public class Teacher {
    private int id;
    private String name;
}

连接SqlSession

package com.my.utils;

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 java.io.IOException;
import java.io.InputStream;

//sqlSessionFactory  构建sqlSession
public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        try{
            //使用mybatis第一步 获取sqlSessionFactory对象
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession(true);
    }
}

资源文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--核心配置文件-->
<mapper namespace="com.my.dao.StudentMapper">




</mapper>

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--核心配置文件-->
<mapper namespace="com.my.dao.TeacherMapper">




</mapper>

<?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">
<!--核心配置文件-->
<configuration>

    <!--  引入外部配置文件-->
    <properties resource="pp.properties"/>

    <settings>
        <!--    标准的日志工厂-->

        <setting name="logImpl" value="STDOUT_LOGGING"/>
       <!-- <setting name="logImpl" value="LOG4J"/>-->

    </settings>


    <!--给实体类起别名-->
    <typeAliases>

        <package name="com.my.pojo"/>
    </typeAliases>



    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/><!--事务管理-->
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper class="com.my.dao.TeacherMapper"/>
        <mapper class="com.my.dao.StudentMapper"/>


    </mappers>


</configuration>

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis?useSSL=true&userUnicode=true&characterEncoding=UTF-8
username=root
password=123456

测试类

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

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

}

pom配置

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>MyBatis-Study</artifactId>
        <groupId>org.example</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>mybatis-06</artifactId>
    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.12</version>

        </dependency>

    </dependencies>

</project>

运行结果