IDEA使用MyBatis出现的常见错误及解决办法

一、IDEA使用MyBatis出现java.io.IOException: Could not find resource mybatis-config.xml错误解决办法

1.错误现象

java.io.IOException: Could not find resource mybatis-config.xml
at org.apache.ibatis.io.Resources.getResourceAsStream(Resources.java:114)
at org.apache.ibatis.io.Resources.getResourceAsStream(Resources.java:100)
at com.sdbi.test.TestFindBySid.main(TestFindBySid.java:16)

Process finished with exit code 0

错误的意思是：找不到资源文件mybatis-config.xml

2.解决办法

将资源文件mybatis-config.xml所在的config文件夹Mark Directory as成Resources Root

方法一：

方法二：

二、Mapper的命名空间为空

1.错误现象

### Error building SqlSession.
### The error may exist in mapper/UserMapper.xml
### Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'mapper/UserMapper.xml'. Cause: org.apache.ibatis.builder.BuilderException: Mapper's namespace cannot be empty

2.解决办法

修改UserMapper.xml文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!-- mapper为映射根节点 -->
<mapper namespace="com.sdbi.pojo.User">
    <!-- id是接口中的“方法名”，parameterType是传入参数的数据类型，resultType是返回的实体类名（包名.类名）-->
    <select id="findByName" parameterType="String" resultType="com.sdbi.pojo.User">
        select *
        from tb_users
        where name = #{name}
    </select>
</mapper>

三、UserMapper.xml文件中的SQL语句ID和业务逻辑代码中调用的SQL语句名称不一致

1.错误现象

### Error querying database. Cause: java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for findByName
### Cause: java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for findByName