Caused by: java.lang.ClassNotFoundException: Cannot find class: Student

ava.lang.ExceptionInInitializerError
	at MyTest.testStudent(MyTest.java:23)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)
Caused by: org.apache.ibatis.exceptions.PersistenceException: 
### Error building SqlSession.
### The error may exist in com/dao/StudentMapper.xml
### The error occurred while processing mapper_resultMap[StudentTeacher]
### Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: org.apache.ibatis.builder.BuilderException: Error parsing Mapper 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 com.utils.MybatisUtils.<clinit>(MybatisUtils.java:21)
	... 23 more
Caused by: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: org.apache.ibatis.builder.BuilderException: Error parsing Mapper 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:120)
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.parse(XMLConfigBuilder.java:98)
	at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:78)
	... 25 more
Caused by: org.apache.ibatis.builder.BuilderException: Error parsing Mapper 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:120)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.parse(XMLMapperBuilder.java:92)
	at org.apache.ibatis.builder.annotation.MapperAnnotationBuilder.loadXmlResource(MapperAnnotationBuilder.java:173)
	at org.apache.ibatis.builder.annotation.MapperAnnotationBuilder.parse(MapperAnnotationBuilder.java:124)
	at org.apache.ibatis.binding.MapperRegistry.addMapper(MapperRegistry.java:72)
	at org.apache.ibatis.session.Configuration.addMapper(Configuration.java:728)
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.mapperElement(XMLConfigBuilder.java:377)
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:118)
	... 27 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.XMLMapperBuilder.resultMapElement(XMLMapperBuilder.java:265)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElement(XMLMapperBuilder.java:252)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElements(XMLMapperBuilder.java:244)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:116)
	... 34 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)
	... 38 more
Caused by: java.lang.ClassNotFoundException: Cannot find class: Student
	at org.apache.ibatis.io.ClassLoaderWrapper.classForName(ClassLoaderWrapper.java:200)
	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)
	... 40 more


Process finished with exit code -1

出错原因：

resultMap里的type，association里的javaType，select里的resultMap都没有写全类名

   <select id="getStudent" resultMap="StudentTeacher">
        select * from student
    </select>
    <resultMap id="StudentTeacher" type="Student">
        <result property="id" column="id"/>
        <result property="name" column="name"/>
      <!--  复杂的属性，我们需要单独处理 对象:association  集合:collection-->
        <association property="teacher" column="tid" javaType="Teacher" select="getTeacher"/>
    </resultMap>

    <select id="getTeacher" resultType="Teacher">
        select * from teacher where id=#{id}
    </select>

解决方法：

1.写上全类名，从包名开始到实体类名

2.在mybatis的核心配置文件中给实体类配置别名

    <typeAliases>
        <package name="com.dao.pojo"/>
    </typeAliases>

使用包扫描，将pojo包下的所有实体类都赋予一个首字母小写（小驼峰命名法）的别名，使用时直接调用别名即可。

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