Mybatis查询返回null

::: hljs-right DATE: November 7, 2024 :::

Entity中的属性命名不能有下划线，

@TableId
private Long classid;
private String classname;
private Long teacherid;
private Long registrationcode;

public void setTeacherid(Long teacherid) {
	this.teacherid = teacherid;
}

如果sql中列是有下划线的，在`.xml`中映射即可，
```xml
<resultMap type="com.entity.ClassEntity" id="classesMap">
    <result property="classid" column="class_id"/>
    <result property="classname" column="class_name"/>
    <result property="teacherid" column="teacher_id"/>
    <result property="registrationcode" column="registration_code"/>
</resultMap>

感谢coder_wccc: https://blog.csdn.net/qq_36428437/article/details/75309227?spm=1001.2014.3001.5502