Mybatis-解决属性名和字段名不一致问题

墨蓝 2022-11-27 12:19 162阅读 0赞

### 当数据库字段名和类属性名不一致时，查询的结果出现了null值 ###

###### 数据库中的表如下 ######

**users(id,username,password)**  
**Java类**

public class user { 
        private int id;
        private String username;
        private String psw;
    
        @Override
        public String toString() { 
            return "user{" +
                    "id=" + id +
                    ", username='" + username + '\'' +
                    ", psw='" + psw + '\'' +
                    '}';
        }
    
        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 getPsw() { 
            return psw;
        }
    
        public void setPsw(String psw) { 
            this.psw = psw;
        }
    }

#### 解决方案 ####

##### 1、把字段名和属性名设置为一致的 #####

##### 2、使用结果集映射 ResultMap #####

<resultMap id="UserMap" type="User">
        
        <id column="id" property="id"/>
        
        <result column="username" property="username"/>
        <result column="password" property="psw"/>
    </resultMap>
    
    <select id="selectUserById" resultMap="UserMap">
        select id , name , password from user where id = #{id}
    </select>

##### 3、取别名![在这里插入图片描述][20201004153007860.png_pic_center] #####

**这个也是通过第二种方式解决的：**  
[Mybatis多表连接查询字段相同内容被覆盖的问题][Mybatis]

[20201004153007860.png_pic_center]: /images/20221124/3dbe568a3146465aad96122a04588956.png
[Mybatis]: https://blog.csdn.net/weixin_43725517/article/details/107581733