MyBatis多表查询和注解开发

文章目录

• Mybatis多表查询
• • 一对一查询
  • • 一对一查询的模型
    • 一对一查询的语句
    • 创建Order和User实体
    • 创建OrderMapper接口
    • 配置OrderMapper.xml
    • 测试结果
    • 一对多查询
    • • 一对多查询的模型
      • 一对多查询的语句
      • 修改User实体
      • 创建UserMapper接口
      • 配置UserMapper.xml
      • 测试结果
      • 多对多查询
      • • 多对多查询的模型
        • 多对多查询的语句
        • 创建Role实体，修改User实体
        • 添加UserMapper接口方法
        • 配置UserMapper.xml
        • 测试结果
        • Mybatis的注解开发
        • • MyBatis的常用注解
          • MyBatis的增删改查
          • MyBatis的注解实现复杂映射开发
          • 一对一查询
          • • 一对一查询的模型
            • 一对一查询的语句
            • 创建Order和User实体
            • 创建OrderMapper接口
            • 使用注解配置Mapper
            • 测试结果
            • 一对多查询
            • • 一对多查询的模型
              • 一对多查询的语句
              • 修改User实体
              • 创建UserMapper接口
              • 使用注解配置Mapper
              • 测试结果
              • 多对多查询
              • • 多对多查询的模型
                • 多对多查询的语句
                • 创建Role实体，修改User实体
                • 添加UserMapper接口方法
                • 使用注解配置Mapper
                • ���试结果

                  Mybatis多表查询

                  一对一查询

                  一对一查询的模型

                  用户表和订单表的关系为，一个用户有多个订单，一个订单只从属于一个用户

                  一对一查询的需求：查询一个订单，与此同时查询出该订单所属的用户

                  一对一查询的语句

                  对应的sql语句：

                  SELECT *,o.id oid FROM orders o,USER u WHERE o.uid=u.id;

                  查询的结果如下：

                  创建Order和User实体

                  public class Order {    private int id;    private Date ordertime;    private double total;    //代表当前订单从属于哪一个客户    private User user;}public class User {        private int id;    private String username;    private String password;    private Date birthday;}

                  创建OrderMapper接口

                  public interface OrderMapper {    List findAll();}

                  配置OrderMapper.xml

                                                                      SELECT *,o.id oid FROM orders o,USER u WHERE o.uid=u.id    

                  其中还可以配置如下：

                  测试结果

                  OrderMapper mapper = sqlSession.getMapper(OrderMapper.class);List all = mapper.findAll();for(Order order : all){    System.out.println(order);}

                  输出：

                  一对多查询

                  一对多查询的模型

                  用户表和订单表的关系为，一个用户有多个订单，一个订单只从属于一个用户

                  一对多查询的需求：查询一个用户，与此同时查询出该用户具有的订单

                  一对多查询的语句

                  对应的sql语句：

                  select *,o.id oid from user u left join orders o on u.id=o.uid;

                  查询的结果如下：

                  修改User实体

                  public class Order {    private int id;    private Date ordertime;    private double total;    //代表当前订单从属于哪一个客户    private User user;}public class User {        private int id;    private String username;    private String password;    private Date birthday;    //代表当前用户具备哪些订单    private List orderList;}

                  创建UserMapper接口

                  public interface UserMapper {    List findAll();}

                  配置UserMapper.xml

                                                                                                                          select *,o.id oid from user u left join orders o on u.id=o.uid    

                  测试结果

                  UserMapper mapper = sqlSession.getMapper(UserMapper.class);List all = mapper.findAll();for(User user : all){    System.out.println(user.getUsername());    List orderList = user.getOrderList();    for(Order order : orderList){        System.out.println(order);    }    System.out.println("----------------------------------");}

                  输出：

                  15:00:24,330 DEBUG findAll:159 - ==>  Preparing: select u.id uid,u.username ,o.id oid,o.ordertime,o.total from user u left join orders o on u.id=o.uid 15:00:24,360 DEBUG findAll:159 - ==> Parameters: 15:00:24,393 DEBUG findAll:159 - id=1, username='admin', password='null', birthday=null, roleList=null, orderList=[Order{id=1, ordertime=Sun Apr 16 14:23:50 CST 2023, total=2000.0, user=null}]}User{id=2, username='共饮一杯无666', password='null', birthday=null, roleList=null, orderList=[Order{id=2, ordertime=Sun Apr 16 14:23:50 CST 2023, total=8888.0, user=null}]}User{id=3, username='共饮一杯无', password='null', birthday=null, roleList=null, orderList=[Order{id=3, ordertime=Sun Apr 16 14:23:50 CST 2023, total=3699.0, user=null}]}User{id=4, username='共饮一杯无', password='null', birthday=null, roleList=null, orderList=[]}User{id=5, username='共饮一杯无', password='null', birthday=null, roleList=null, orderList=[]}    private int id;    private String username;    private String password;    private Date birthday;    //代表当前用户具备哪些订单    private List    private int id;    private String rolename;}    System.out.println(user.getUsername());    List        System.out.println(role);    }    System.out.println("----------------------------------");}

                  pre 11:45:51,443 DEBUG findUserAndRoleAll:159 - ==> Preparing: SELECT * FROM USER u,sys_user_role ur,sys_role r WHERE u.id=ur.userId AND ur.roleId=r.id 11:45:51,572 DEBUG findUserAndRoleAll:159 - ==> Parameters: User{id=1, username='zjq', password='abc', birthday=Wed Jul 28 00:00:00 GMT+08:00 2021, roleList=[Role{id=1, roleName='CTO', roleDesc='CTO'}, Role{id=2, roleName='COO', roleDesc='COO'}]}User{id=2, username='jack', password='123456', birthday=Fri Aug 20 00:00:00 GMT+08:00 2021, roleList=[Role{id=1, roleName='CTO', roleDesc='CTO'}, Role{id=2, roleName='COO', roleDesc='COO'}]}11:45:51,610 DEBUG findUserAndRoleAll:159 - InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml"); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream); SqlSession sqlSession = sqlSessionFactory.openSession(true); userMapper = sqlSession.getMapper(UserMapper.class);}@Testpublic void testAdd() { User user = new User(); user.setUsername("测试数据"); user.setPassword("123"); user.setBirthday(new Date()); userMapper.add(user);}@Testpublic void testUpdate() throws IOException { User user = new User(); user.setId(16); user.setUsername("测试数据修改"); user.setPassword("abc"); user.setBirthday(new Date()); userMapper.update(user);}@Testpublic void testDelete() throws IOException { userMapper.delete(16);}@Testpublic void testFindById() throws IOException { User user = userMapper.findById(1); System.out.println(user);}@Testpublic void testFindAll() throws IOException { List System.out.println(user); }} private int id; private Date ordertime; private double total; //代表当前订单从属于哪一个客户 private User user;}public class User { private int id; private String username; private String password; private Date birthday;} List @Select("select * from orders") @Results({ @Result(id=true,property = "id",column = "id"), @Result(property = "ordertime",column = "ordertime"), @Result(property = "total",column = "total"), @Result(property = "user",column = "uid", javaType = User.class, one = @One(select = "com.zjq.mapper.UserMapper.findById")) }) List @Select("select * from user where id=#{id}") User findById(int id); } List System.out.println(order); }} private int id; private Date ordertime; private double total; //代表当前订单从属于哪一个客户 private User user;}public class User { private int id; private String username; private String password; private Date birthday; //代表当前用户具备哪些订单 private List @Select("select * from user") @Results({ @Result(id = true,property = "id",column = "id"), @Result(property = "username",column = "username"), @Result(property = "password",column = "password"), @Result(property = "birthday",column = "birthday"), @Result(property = "orderList",column = "id", javaType = List.class, many = @Many(select = "com.zjq.mapper.OrderMapper.findByUid")) }) List @Select("select * from orders where uid=#{uid}") List System.out.println(user.getUsername()); List System.out.println(order); } System.out.println("-----------------------------");} private int id; private String username; private String password; private Date birthday; //代表当前用户具备哪些订单 private List private int id; private String rolename;} @Select("select * from user") @Results({ @Result(id = true,property = "id",column = "id"), @Result(property = "username",column = "username"), @Result(property = "password",column = "password"), @Result(property = "birthday",column = "birthday"), @Result(property = "roleList",column = "id", javaType = List.class, many = @Many(select = "com.zjq.mapper.RoleMapper.findByUid"))})List @Select("select * from role r,user_role ur where r.id=ur.role_id and ur.user_id=#{uid}") List System.out.println(user.getUsername()); List System.out.println(role); } System.out.println("----------------------------------");}