MyBatis注解开发 | MyBatis

1.常用注解

@Insert     新增
@Update     更新
@Delete     删除
@Select     查询
@Result     结果集
@Results    封装多个结果集
@One        一对一结果集
@Many       一对多结果集 

• 注解代替Mapper.xml文件

  • mapper.UserMapper

    public interface UserMapper {
        /**
         * 基本操作
         */
        @Insert("insert into user values(#{id},#{username},#{password},#{birthday})")
        public void save(User user);
    
        @Update("update user set username=#{username},password=#{password} where id=#{id}")
        public void update(User user);
    
        @Delete("delete from user where id=#{id}")
        public void delete(int id);
    
        @Select("select * from user where id=#{id}")
        public User findById(int id);
    
        @Select("select * from user")
        public List<User> findAll();
    
        /**
         * 一对多
         */
        @Select("select * from user")
        @Results({
                @Result(id=true ,column = "id",property = "id"),
                @Result(column = "username",property = "username"),
                @Result(column = "password",property = "password"),
                @Result(
                    property = "orderList",
                    column = "id",
                    javaType = List.class,
                    many = @Many(select = "com.itheima.mapper.OrderMapper.findByUid")
                )
        })
        public List<User> findUserAndOrderAll();
    
        @Select("SELECT * FROM USER")
        @Results({
                @Result(id = true,column = "id",property = "id"),
                @Result(column = "username",property = "username"),
                @Result(column = "password",property = "password"),
                @Result(
                    property = "roleList",
                    column = "id",
                    javaType = List.class,
                    many = @Many(select = "com.itheima.mapper.RoleMapper.findByUid")
                )
        })
        public List<User> findUserAndRoleAll();
    }
    

  • mapper.OrderMapper

    public interface OrderMapper {
        @Select("select * from orders where uid=#{uid}")
        public List<Order> findByUid(int uid);
    
        /**
         * 一对一 方式二.两张表分开查
         */
        @Select("select * from orders")
        @Results({
                @Result(column = "id",property = "id"),
                @Result(column = "ordertime",property = "ordertime"),
                @Result(column = "total",property = "total"),
                @Result(
                    property = "user", //要封装的属性名称
                    column = "uid", //根据那个字段去查询user表的数据
                    javaType = User.class, //要封装的实体类型
                    //select属性 代表查询那个接口的方法获得数据
                    one = @One(select = "com.itheima.mapper.UserMapper.findById")
                )
        })
        public List<Order> findAll();
    
        /** 
         * 一对一 方式一.两张表一起查
         */
        /*@Select("select *,o.id oid from orders o,user u where o.uid=u.id")
        @Results({
            @Result(column = "oid",property = "id"),
            @Result(column = "ordertime",property = "ordertime"),
            @Result(column = "total",property = "total"),
            @Result(column = "uid",property = "user.id"),
            @Result(column = "username",property = "user.username"),
            @Result(column = "password",property = "user.password")
        })
        public List<Order> findAll();*/
    }
    

  • mapper.RoleMapper

    public interface RoleMapper {
        @Select("SELECT * FROM sys_user_role ur,sys_role r WHERE ur.roleId=r.id AND ur.userId=#{uid}")
        public List<Role> findByUid(int uid);
    }
    

  • 加载映射关系

    <mappers>
        <package name="com.miaokela.mapper"></package>
    </mappers>
    

  • 附录(模型类)：

    domain.User

    public class User {
    
        private int id;
        private String username;
        private String password;
        private Date birthday;
    
        //当前用户具备哪些角色
        private List<Role> roleList;
    
        public List<Role> getRoleList() {
            return roleList;
        }
    
        public void setRoleList(List<Role> roleList) {
            this.roleList = roleList;
        }
    
        /*//描述的是当前用户具有的订单
        private List<Order> orderList;
        public List<Order> getOrderList() {
            return orderList;
        }
        public void setOrderList(List<Order> orderList) {
            this.orderList = orderList;
        }*/
    
        public Date getBirthday() {
            return birthday;
        }
    
        public void setBirthday(Date birthday) {
            this.birthday = birthday;
        }
    
        public int getId() {
            return id;
        }
    
        public void setId(int id) {
            this.id = id;
        }
    
        public String getUsername() {
            return username;
        }
    
        public void setUsername(String username) {
            this.username = username;
        }
    
        public String getPassword() {
            return password;
        }
    
        public void setPassword(String password) {
            this.password = password;
        }
    
        @Override
        public String toString() {
            return "User{" +
                    "id=" + id +
                    ", username='" + username + '\'' +
                    ", password='" + password + '\'' +
                    ", birthday=" + birthday +
                    ", roleList=" + roleList +
                    '}';
        }
    }
    

    domain.Order

    public class Order {
    
        private int id;
        private Date ordertime;
        private double total;
    
        //当前订单属于哪一个用户
        private User user;
    
        public int getId() {
            return id;
        }
    
        public void setId(int id) {
            this.id = id;
        }
    
        public Date getOrdertime() {
            return ordertime;
        }
    
        public void setOrdertime(Date ordertime) {
            this.ordertime = ordertime;
        }
    
        public double getTotal() {
            return total;
        }
    
        public void setTotal(double total) {
            this.total = total;
        }
    
        public User getUser() {
            return user;
        }
    
        public void setUser(User user) {
            this.user = user;
        }
    
        @Override
        public String toString() {
            return "Order{" +
                    "id=" + id +
                    ", ordertime=" + ordertime +
                    ", total=" + total +
                    ", user=" + user +
                    '}';
        }
    }
    

    domain.Role

    public class Role {
    
        private int id;
        private String roleName;
        private String roleDesc;
    
        public int getId() {
            return id;
        }
    
        public void setId(int id) {
            this.id = id;
        }
    
        public String getRoleName() {
            return roleName;
        }
    
        public void setRoleName(String roleName) {
            this.roleName = roleName;
        }
    
        public String getRoleDesc() {
            return roleDesc;
        }
    
        public void setRoleDesc(String roleDesc) {
            this.roleDesc = roleDesc;
        }
    
        @Override
        public String toString() {
            return "Role{" +
                    "id=" + id +
                    ", roleName='" + roleName + '\'' +
                    ", roleDesc='" + roleDesc + '\'' +
                    '}';
        }
    }