Mybatis配置了类的别名但是在mapper配置文件中使用时报错无法找到

背景如下：
实体类Student加上了Alias注解，命名为Student

在某个Mapper的配置文件中resultType设置为了Student

<mapper namespace="mapper.TestMapper">
    <select id="selectStudent" resultType="Student">
        select * from student
    </select>
</mapper>

但是就是在运行时报错

Exception in thread "main" java.lang.ExceptionInInitializerError
	at Main.main(Main.java:13)
Caused by: org.apache.ibatis.exceptions.PersistenceException: 
### Error building SqlSession.
### The error may exist in mapper/TestMapper.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/TestMapper.xml'. Cause: org.apache.ibatis.builder.BuilderException: Error resolving class. Cause: org.apache.ibatis.type.TypeException: Could not resolve type alias 'Student'.  Cause: java.lang.ClassNotFoundException: Cannot find class: Student
	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
	at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:80)
	at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:64)
	at MybatisUtil.<clinit>(MybatisUtil.java:14)
	... 1 more
Caused by: 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/TestMapper.xml'. Cause: org.apache.ibatis.builder.BuilderException: Error resolving class. Cause: org.apache.ibatis.type.TypeException: Could not resolve type alias 'Student'.  Cause: java.lang.ClassNotFoundException: Cannot find class: Student
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:122)
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.parse(XMLConfigBuilder.java:99)
	at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:78)
	... 3 more
Caused by: org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'mapper/TestMapper.xml'. Cause: org.apache.ibatis.builder.BuilderException: Error resolving class. Cause: org.apache.ibatis.type.TypeException: Could not resolve type alias 'Student'.  Cause: java.lang.ClassNotFoundException: Cannot find class: Student
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:123)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.parse(XMLMapperBuilder.java:95)
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.mapperElement(XMLConfigBuilder.java:379)
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:120)
	... 5 more
Caused by: org.apache.ibatis.builder.BuilderException: Error resolving class. Cause: org.apache.ibatis.type.TypeException: Could not resolve type alias 'Student'.  Cause: java.lang.ClassNotFoundException: Cannot find class: Student
	at org.apache.ibatis.builder.BaseBuilder.resolveClass(BaseBuilder.java:118)
	at org.apache.ibatis.builder.xml.XMLStatementBuilder.parseStatementNode(XMLStatementBuilder.java:102)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.buildStatementFromContext(XMLMapperBuilder.java:138)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.buildStatementFromContext(XMLMapperBuilder.java:131)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:121)
	... 8 more
Caused by: org.apache.ibatis.type.TypeException: Could not resolve type alias 'Student'.  Cause: java.lang.ClassNotFoundException: Cannot find class: Student
	at org.apache.ibatis.type.TypeAliasRegistry.resolveAlias(TypeAliasRegistry.java:120)
	at org.apache.ibatis.builder.BaseBuilder.resolveAlias(BaseBuilder.java:149)
	at org.apache.ibatis.builder.BaseBuilder.resolveClass(BaseBuilder.java:116)
	... 12 more
Caused by: java.lang.ClassNotFoundException: Cannot find class: Student
	at org.apache.ibatis.io.ClassLoaderWrapper.classForName(ClassLoaderWrapper.java:196)
	at org.apache.ibatis.io.ClassLoaderWrapper.classForName(ClassLoaderWrapper.java:89)
	at org.apache.ibatis.io.Resources.classForName(Resources.java:261)
	at org.apache.ibatis.type.TypeAliasRegistry.resolveAlias(TypeAliasRegistry.java:116)
	... 14 more

观察原因发现是找不到Student类，奇怪的是我们已经起好了别名鸭～( ╯□╰ )
查看mybatis官网有关别名的表述

也就是说我们的别名要配合package标签使用，用来指明应该搜索的包名～

修改方案：
在最外层配置文件中增加typeAliases标签，同时把具体实体类的包名写上去一定要注意外层配置文件中的标签顺序，这个东西有说法的~

<typeAliases>
    <package name="entity"/>
</typeAliases>

PS：实践中发现，在主配置文件中作此修改后，就算Student去掉Alias注解依旧可以正常使用~ 肥肠方便呢OvO