Mybatis学习笔记（六）注解开发_mybatis的注解开发学习笔记

MyBatis注解开发

注解方式比较简单，但是实际开发不推荐使用注解，使用配置文件的方式，不需要改源代码.

@Insert:添加
@Update:修改
@Delete:删除
@Select:查询
@Result:实现结果集封装
@Results:可以和@Result一起使用，封装多个结果集
@One:实现一对一和多对一的结果集封装
@Many:实现一对多结果级封装
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一、使用注解完成CRUD

1. SqlMapConfig.xml配置文件

<mappers>
        <!--第一种方式：class引入接口，只能引入一个接口-->
        <mapper class="com.qcby.dao.UserAnnoDao"/>
        
        <!--第二种方式：针对com.qcby.dao包下的所有的接口-->
        <package name="com.qcby.dao"/>
</mappers>
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2. UserDao接口方法和注解的编写

import com.qcby.entity.User;
import org.apache.ibatis.annotations.*;

import javax.jws.soap.SOAPBinding;
import java.util.List;

public interface UserDao {
    //查询所有
    @Select("select * from user")
    @Results(id="userMap",value = {
            @Result(property = "id",column = "id"),
            @Result(property = "username",column = "username"),
            @Result(property = "birthday",column = "birthday"),
            @Result(property = "sex",column = "sex"),
            @Result(property = "address",column = "address")
    })
    public List<User> findAll();
    
    //通过ID查询
    @Select("select * from user where id = #{id}")
    @ResultMap(value = "userMap")
    public User findById(int id);

    //增加
    @Insert("insert into user(username,birthday,sex,address) values(#{username},#{birthday},#{sex},#{address})")
    @SelectKey(statement="select last_insert_id()",keyColumn = "id",keyProperty = "id",before =false,resultType =Integer.class)
    public int insert(User user);

    //更新
    @Update("update user set username = #{username},birthday = #{birthday},sex = #{sex},address = #{address} where id = #{id}")
    public int update(User user);

    //删除
    @Delete("delete from user where id = #{id}")
    public int delete(int id);

    //查询数量
    @Select("select count(*) from user")
    public int findCount();

    //模糊查询
    @Select("select * from user where username like #{username}")
    public List<User> findByName(String username);

}
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3. UserTest测试方法的编写

public class UserTest {
    private InputStream in = null;
    private SqlSession session = null;
    private UserDao mapper = null;

    @Before  //前置通知, 在方法执行之前执行
    public void init() throws IOException {
        //加载主配置文件，目的是为了构建SqlSessionFactory对象
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //创建SqlSessionFactory对象
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
        //通过SqlSessionFactory工厂对象创建SqlSesssion对象
        session = factory.openSession();
        //通过Session创建UserDao接口代理对象
        mapper = session.getMapper(UserDao.class);
    }

    @After  //@After: 后置通知, 在方法执行之后执行 。
    public void destory() throws IOException {
        //释放资源
        session.close();
        in.close();
    }

    /**
     * 测试查询所有的方法
     */
    @Test
    public void findAll() throws IOException {
        List<User> users = mapper.findAll();
        for (User user:users) {
            System.out.println(user.toString());
        }
    }

    @Test
    public void findById(){
        User user = mapper.findById(4);
        System.out.println(user.toString());
    }

    @Test
    public void insert(){
        User user = new User();
        user.setSex("女");
        user.setUsername("小美");
        user.setBirthday(new Date());
        user.setAddress("保定");
        int insert = mapper.insert(user);
        session.commit();
        System.out.println(insert);
    }


    @Test
    public void update(){
        User user = new User();
        user.setId(22);
        user.setSex("女");
        user.setUsername("小美");
        user.setBirthday(new Date());
        user.setAddress("上海");
        int insert = mapper.update(user);
        session.commit();
        System.out.println(insert);
    }

    @Test
    public void delete(){
       int delete =  mapper.delete(22);
       session.commit();
        System.out.println(delete);
    }

    @Test
    public void findCount(){
        int count = mapper.findCount();
        session.commit();
        System.out.println(count);
    }

    @Test
    public void findByName(){
        List<User> list  = mapper.findByName("%a%");
        for (User user : list) {
            System.out.println(user);
        }
        session.close();
    }

}

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二、多对一的注解查询

1.多对一立即加载查询

①.StudentDao接口的方法编写

@Select(" SELECT  student.*,teacher.Tname FROM student LEFT JOIN teacher  on student.t_id = teacher.id")
@Results(value = {
        @Result(property = "id",column = "id"),
        @Result(property = "Sname",column = "Sname"),
        @Result(property = "sex",column = "sex"),
        @Result(property = "age",column = "age"),
        @Result(property = "t_id",column = "t_id"),
        @Result(property = "teacher.Tname",column = "Tname")
})
public List<Student> getStudent();
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②.进行测试

@Test
public void getStudent(){
    List<Student> student = mapper.getStudent();
    for (Student student1:student) {
        System.out.println(student1.toString());
    }
}

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2.多对一延迟加载查询

①.StudentDao接口的方法编写

@Select("select * from student")
@Results(value = {
        @Result(property = "id",column = "id"),
        @Result(property = "Sname",column = "Sname"),
        @Result(property = "sex",column = "sex"),
        @Result(property = "age",column = "age"),
        @Result(property = "teacher",column = "t_id",one=@One(select = "com.qcby.dao.TeacherDao.getTeacher",fetchType = FetchType.LAZY))
})
public List<Student> getStudent();
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②.TeacherDao接口的方法编写

@Select("select  * from  teacher where id = #{t_id}")
Teacher getTeacher(Integer id);
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③.进行测试

@Test
public void getStudent(){
    List<Student> student = mapper.getStudent();
    for (Student student1:student) {
        System.out.println(student1.toString());
    }
}

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三、一对多的注解查询

一对多查询，使用延迟加载的方式查询

①.TeacherDao接口的方法编写

//查询所有延迟加载
@Select("select * from Teacher")
@Results(value = {
        @Result(property = "id",column = "id"),
        @Result(property = "Tname",column = "Tname"),
        @Result(property = "students",column = "id",many =@Many(select = "com.qcby.dao.StudentDao.findByUid",fetchType = FetchType.LAZY))
})
public List<Teacher> findAllLazy();
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②.StudentDao接口的方法编写

@Select("select * from student where t_id = #{t_id}")
public Student findByUid(int uid);
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③.进行测试

@Test
public void findAllLazy(){
    List<Teacher> list =  mapper.findAllLazy();
    for (Teacher teacher: list) {
        System.out.println(teacher.toString());
    }
}
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