Mybatis 笔记 019（复杂查询环境搭建）

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1. SQL

CREATE TABLE `teacher`(
	`id` INT(10) NOT NULL,
	`name` VARCHAR(30) DEFAULT NULL,
	PRIMARY KEY(`id`)
) ENGINE=INNODB DEFAULT CHARSET=UTF8;

INSERT INTO `teacher`(`id`, `name`) VALUES(1, '默老师');

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`)
) ENGINE=INNODB DEFAULT CHARSET=UTF8;

INSERT INTO `student`(`id`, `name`, `tid`) VALUES
(1, '俏如来', 1),
(2, '雁王', 1),
(3, '欲星移', 1),
(4, '凰后', 1),
(5, '砚寒清', 1);

2. 配置文件

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 核心配置文件-->
<configuration>

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

    <settings>
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>

    <!-- 可以给实体类起别名 -->
    <typeAliases>
        <package name="org.example.mybatis06.pojo"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <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>

    <!-- 绑定接口-->
    <mappers>
        <package name="org.example.mybatis06.mapper"/>
    </mappers>

</configuration>

db.properties

driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/study_mybatis?useSSL=true&useUnicode=true&characterEncoding=UTF-8&serverTimezone=GMT%2B8
username=root
password=root

3. 实体类

package org.example.mybatis06.pojo;

import lombok.Data;

@Data
public class Teacher {

    private Integer id;
    private String name;

}

package org.example.mybatis06.pojo;

import lombok.Data;

@Data
public class Student {

    private Integer id;
    private String name;
    private Teacher teacher;

}

4. 接口

package org.example.mybatis06.mapper;

import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import org.example.mybatis06.pojo.Teacher;

public interface TeacherMapper {

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

}

<?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">
<mapper namespace="org.example.mybatis06.mapper.TeacherMapper">
</mapper>

package org.example.mybatis06.mapper;

public interface StudentMapper {
}

<?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">
<mapper namespace="org.example.mybatis06.mapper.StudentMapper">
</mapper>

5. 工具类

package org.example.mybatis06.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;

public class MybatisUtils {

    private static SqlSessionFactory sqlSessionFactory;

    static {
        try {
            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();
    }

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

}

6. 测试类

package org.example.mybatis06.mapper;

import org.apache.ibatis.session.SqlSession;
import org.example.mybatis06.utils.MybatisUtils;
import org.junit.Test;

public class TeacherMapperTest {

    @Test
    public void testGetTeacher() {
        try (SqlSession sqlSession = MybatisUtils.getSqlSession()) {
            System.out.println(sqlSession.getMapper(TeacherMapper.class).getTeacher(1));
        }
    }

}