一对多处理
运用场景: 一个老师有多名学生, 对于老师而言 就是一对多
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Teacher实体类
@Data
public class Teacher {
private int id;
private String name;
List<Student> students;
}
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mybatis-config.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<properties resource="db.properties">
</properties>
<settings>
<!--标准的日志工厂实现-->
<setting name="logImpl" value="STDOUT_LOGGING"/>
</settings>
<typeAliases>
<!-- <package name="com.kuang.pojo"/>-->
<typeAlias type="com.kuang.pojo.Teacher" alias="Teacher"/>
</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>
<environment id="test">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false&useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&serverTimezone=GMT%2B8"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper class="com.kuang.mapper.TeacherMapper"/>
</mappers>
</configuration>
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TeacherMapper.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.kuang.mapper.TeacherMapper">
<select id="getTeacher" resultMap="TeacherStudent">
select s.id sid,s.name sname,s.tid stid,t.id tid,t.name tname from mybatis.teacher t
join mybatis.student s on s.tid = t.id
where t.id = #{tid}
</select>
<resultMap id="TeacherStudent" type="Teacher">
<result property="id" column="tid"/>
<result property="name" column="tname"/>
<!--复杂的属性,我们需要单独处理 对象:association 集合:collection
javaType 指定属性类型!
集合中的泛型信息,我们使用ofType获取
-->
<collection property="students" ofType="Student">
<result property="id" column="sid"/>
<result property="name" column="sname"/>
<result property="tid" column="stid"/>
</collection>
</resultMap>
</mapper>
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公共类
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(true);
}
}
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测试
@Test
public void getTeacher(){
SqlSession sqlSession = MybatisUtils.getSqlSession();
TeacherMapper mapper = sqlSession.getMapper(TeacherMapper.class);
Teacher teacher = mapper.getTeacher(1);
System.out.println("teacher = " + teacher);
sqlSession.close();
}
}
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输出结果
teacher = Teacher(id=1, name=秦老师, students=[Student(id=1, name=小明, tid=1), Student(id=2, name=小红, tid=1), Student(id=3, name=小张, tid=1), Student(id=4, name=小李, tid=1), Student(id=5, name=小王, tid=1)])
标签：之一,name,处理,teacher,mybatis,tid,Student,Mybatis,id From： https://www.cnblogs.com/kuangshenmentu/p/17761536.html