mybatis基础操作--CRUD（基于注解使用）

环境准备创建表

sql 复制代码

create table dept(id int unsigned primary key auto_increment comment '主键ID',
name varchar(10) not null unique comment '部门名称',
create_time datetime not null comment '创建时间',
update_time datetime not null comment '修改时间'
)comment '部门表';

insert into dept(id, name, create_time, update_time) VALUES
(1,'皇帝',now(),now()),(2,'后宫',now(),now()),(3,'文臣',now(),now()),(4,'武将',now(),now());

create table emp(
id int unsigned primary key auto_increment comment 'ID',
username varchar(20) not null  unique comment '用户名',
password varchar(32) default '123456' comment '密码',
gender tinyint unsigned not null comment '性别',
image varchar(300) comment '图像',
job tinyint unsigned comment '职位',
entrydate date comment '入职时间',
dept_id int unsigned comment '部门ID',
create_time datetime not null comment '创建时间',
update_time datetime not null comment '修改时间'
)comment '员工表'

增删改查

Emp.java

java 复制代码

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Emp {
    private Integer id;
    private String username;
    private String password;
    private Short gender;
    private String image;
    private Short job;
    private LocalDateTime entrydate;
    private Integer deptId;
    private LocalDateTime createTime;
    private LocalDateTime updateTime;
}

EmpMapper.interface

java 复制代码

@Mapper
public interface EmpMapper {
    @Delete("delete from emp where id=#{id}") //预编译 参数传递 防止sql注入
    public void delete(Integer id);

    @Options(keyProperty = "id",useGeneratedKeys = true)//会自动将生成主键值 赋值给emp对象的id属性
    @Insert("insert into emp(id, username, password, gender, image, job, entrydate, dept_id, create_time, update_time) VALUES ( #{id},#{username},#{password},#{gender},#{image},#{job},#{entrydate},#{deptId},#{createTime},#{updateTime})")
    public void insert(Emp emp);

    @Update("update emp set username =#{username},update_time =#{updateTime} where id =#{id}")
    public void update(Emp emp);

    @Select("select * from emp where id =#{id}") //数据封装 如果类属性名和数据库返回的字段名一致会自动封装
    public  Emp getById(Integer id);
    //1.解决方法给字段起别名
//    @Select("select update_time updateTime,dept_id deptId,create_time createTime from emp where id =#{id}") //数据封装 如果类属性名和数据库返回的字段名一致会自动封装
//    public  Emp getById(Integer id);
    //2.通过Result注解手动映射封装
//    @Results({
//            @Result(column = "dept_id",property = "deptId"),
//            @Result(column = "create_time",property = "createTime"),
//            @Result(column = "update_time",property = "updateTime")
//    })
//    @Select("select * from emp where id =#{id}") //数据封装 如果类属性名和数据库返回的字段名一致会自动封装
//    public  Emp getById(Integer id);
    //3.开启mybatis驼峰命名自动映射开关
    // mybatis.configuration.map-underscore-to-camel-case=true

//    @Select("select * from emp where username like '%${name}%' and gender = #{gender} order by create_time desc ")//${}存在sql注入问题
@Select("select * from emp where username like concat('%',#{name},'%') and gender = #{gender} order by create_time desc ")
    public List<Emp> select(String name,Short gender);
}

增删改查注意

查询开启驼峰命名

查询不到主键

模糊查询%朱%->%${朱}%存在sql注入问题使用concat

mybatis log

java 复制代码

mybatis.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl