【MyBatis学习】ExceptionInInitializerError与PersistenceException异常的出现和解决

ExceptionInInitializerError与PersistenceException异常的出现和解决

刚开始学习MyBatis框架，正在进行【MyBatis 使用传统 Dao 开发方式】，运行测试方法testSelect，查询数据库中所有学生信息，但是最后结果出现了错误：

java.lang.ExceptionInInitializerError

可以看到后面还有一个异常

Caused by: org.apache.ibatis.exceptions.PersistenceException:

Error building SqlSession.

The error may exist in com/yuming/dao/StudentDao.xml

运行截图：

完整异常信息：

java.lang.ExceptionInInitializerError
	at com.yuming.dao.StudentDaoImpl.selectStudents(StudentDaoImpl.java:13)
	at com.yuming.TestMyBatis.testSelect(TestMyBatis.java:22)
	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:47)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: org.apache.ibatis.exceptions.PersistenceException: 
### Error building SqlSession.
### The error may exist in com/yuming/dao/StudentDao.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 'com/yuming/dao/StudentDao.xml'. Cause: java.lang.IllegalArgumentException: Mapped Statements collection already contains value for com.yuming.dao.StudentDao.. please check com/yuming/dao/StudentDao.xml and com/yuming/dao/StudentDao.xml
	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.yuming.util.MyBatisUtil.<clinit>(MyBatisUtil.java:21)
	... 24 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 'com/yuming/dao/StudentDao.xml'. Cause: java.lang.IllegalArgumentException: Mapped Statements collection already contains value for com.yuming.dao.StudentDao.. please check com/yuming/dao/StudentDao.xml and com/yuming/dao/StudentDao.xml
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:121)
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.parse(XMLConfigBuilder.java:98)
	at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:78)
	... 26 more
Caused by: org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'com/yuming/dao/StudentDao.xml'. Cause: java.lang.IllegalArgumentException: Mapped Statements collection already contains value for com.yuming.dao.StudentDao.. please check com/yuming/dao/StudentDao.xml and com/yuming/dao/StudentDao.xml
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:122)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.parse(XMLMapperBuilder.java:94)
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.mapperElement(XMLConfigBuilder.java:373)
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:119)
	... 28 more
Caused by: java.lang.IllegalArgumentException: Mapped Statements collection already contains value for com.yuming.dao.StudentDao.. please check com/yuming/dao/StudentDao.xml and com/yuming/dao/StudentDao.xml
	at org.apache.ibatis.session.Configuration$StrictMap.put(Configuration.java:930)
	at org.apache.ibatis.session.Configuration$StrictMap.put(Configuration.java:887)
	at org.apache.ibatis.session.Configuration.addMappedStatement(Configuration.java:686)
	at org.apache.ibatis.builder.MapperBuilderAssistant.addMappedStatement(MapperBuilderAssistant.java:296)
	at org.apache.ibatis.builder.xml.XMLStatementBuilder.parseStatementNode(XMLStatementBuilder.java:110)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.buildStatementFromContext(XMLMapperBuilder.java:137)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.buildStatementFromContext(XMLMapperBuilder.java:130)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:120)
	... 31 more

然后结果多次debug运行测试，发现确实是我com/yuming/dao/StudentDao.xml 这个sql映射文件里面的问题，因为我当时想着一次把别的几个标签也写上了，只不过把id的值先空着在，sql语句也没写，到时候用的时候直接填：

<mapper namespace="com.yuming.dao.StudentDao">

    <select id="selectStudents" resultType="com.yuming.entity.Student">
        select id,name,email,age from student order by id
    select>

    <insert id="">
    insert>

    <delete id="">
    delete>

    <update id="">
    update>

mapper>

然后就是因为我这样做了，导致后面一直不能运行成功，当我把它们删掉之后，就OK了

<mapper namespace="com.yuming.dao.StudentDao">
    
    <select id="selectStudents" resultType="com.yuming.entity.Student">
        select id,name,email,age from student order by id
    select>
    
mapper>

果然有的时候不能太偷懒啊。。

注：我在出现ExceptionInInitializerError异常的时候也百度了很久，发现出现原因有很多种，并没有看到我这种的，目前不知道我的解决方法对不对，先做个记录在这里