好久沒來記錄一下自己的學習情況，最近都在學框架，今天來記錄一下關於mybatis框架的學習過程中碰過的一些問題：
以下內容可能稍微有點凌亂，因為是把之前遇到過的錯誤或異常都集中一起了，不過我已經把問題原因or解決方法加粗了，方便查看，少部分問題是暫時未知原因，如果哪位大神知道原因歡迎留言，我后面如果知道了原因也會對應更新！^ ^
org.apache.ibatis.exceptions.PersistenceException:
### Error building SqlSession.
### The error may exist in SQL Mapper Configuration
### Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: org.apache.ibatis.datasource.DataSourceException: Unknown DataSource property: drvier
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 App_1_type.findById(App_1_type.java:21)
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$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
Class not found: "App_1_type"Empty test suite.
出現這個錯誤的時候，打開maven面板，看看里面有沒有這個模塊的信息（我這次在maven面板找不到目前這個項目）所以在maven面板把當前模塊添加進去即可
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.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: org.apache.ibatis.datasource.DataSourceException: Unknown DataSource property: drvier
at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:121)
at org.apache.ibatis.builder.xml.XMLConfigBuilder.parse(XMLConfigBuilder.java:99)
at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:78)
... 24 more
Caused by: org.apache.ibatis.datasource.DataSourceException: Unknown DataSource property: drvier
at org.apache.ibatis.datasource.unpooled.UnpooledDataSourceFactory.setProperties(UnpooledDataSourceFactory.java:55)
at org.apache.ibatis.builder.xml.XMLConfigBuilder.dataSourceElement(XMLConfigBuilder.java:326)
at org.apache.ibatis.builder.xml.XMLConfigBuilder.environmentsElement(XMLConfigBuilder.java:280)
at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:116)
... 26 more
暫不清楚，只是把前一個項目的driver配置復制過來就OK，然后還原會原來的driver配置也OK了
org.apache.ibatis.exceptions.PersistenceException:
### Error updating database. Cause: org.apache.ibatis.reflection.ReflectionException: There is no getter for property named 'userId111' in 'class com.itheima.entity.User'
### The error may involve com.itheima.dao.IUserDao.delete-Inline
### The error occurred while setting parameters
### SQL: DELETE FROM user WHERE id = ?;
### Cause: org.apache.ibatis.reflection.ReflectionException: There is no getter for property named 'userId111' in 'class com.itheima.entity.User'
at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:200)
at org.apache.ibatis.session.defaults.DefaultSqlSession.delete(DefaultSqlSession.java:213)
at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:67)
at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:59)
at com.sun.proxy.$Proxy5.delete(Unknown Source)
at App_1_type.delete(App_1_type.java:167)
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$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$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.reflection.ReflectionException: There is no getter for property named 'userId111' in 'class com.itheima.entity.User'
at org.apache.ibatis.reflection.Reflector.getGetInvoker(Reflector.java:419)
at org.apache.ibatis.reflection.MetaClass.getGetInvoker(MetaClass.java:164)
at org.apache.ibatis.reflection.wrapper.BeanWrapper.getBeanProperty(BeanWrapper.java:162)
at org.apache.ibatis.reflection.wrapper.BeanWrapper.get(BeanWrapper.java:49)
at org.apache.ibatis.reflection.MetaObject.getValue(MetaObject.java:122)
at org.apache.ibatis.scripting.defaults.DefaultParameterHandler.setParameters(DefaultParameterHandler.java:79)
at org.apache.ibatis.executor.statement.PreparedStatementHandler.parameterize(PreparedStatementHandler.java:93)
at org.apache.ibatis.executor.statement.RoutingStatementHandler.parameterize(RoutingStatementHandler.java:64)
at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:86)
at org.apache.ibatis.executor.SimpleExecutor.doUpdate(SimpleExecutor.java:49)
at org.apache.ibatis.executor.BaseExecutor.update(BaseExecutor.java:117)
at org.apache.ibatis.executor.CachingExecutor.update(CachingExecutor.java:76)
at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:198)
... 27 more
這個異常是因為我接口的方法傳入了對象作為參數，但是在IUserDao.xml里配置的#{}沒有使用對象屬性名字。
解決：把#{}里的內容改為對象的屬性名，或者把接口方法的傳入參數改為int id
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: Parsing error was found in mapping #{}. Check syntax #{property|(expression), var1=value1, var2=value2, ...}
配置文件寫錯！
異常：
org.apache.ibatis.exceptions.PersistenceException:
### Error querying database. Cause: org.apache.ibatis.reflection.ReflectionException: Could not set property 'id' of 'class com.itheima.entity.Account' with value '41' Cause: org.apache.ibatis.reflection.ReflectionException: There is no setter for property named 'id' in 'class com.itheima.entity.Account'
### The error may exist in com/itheima/dao/IUserDao.xml
### The error may involve com.itheima.dao.IUserDao.findAllUser
### The error occurred while handling results
### SQL: select * from user u left join account a on u.id=a.UID
### Cause: org.apache.ibatis.reflection.ReflectionException: Could not set property 'id' of 'class com.itheima.entity.Account' with value '41' Cause: org.apache.ibatis.reflection.ReflectionException: There is no setter for property named 'id' in 'class com.itheima.entity.Account'
java.io.IOException: Could not find resource SqlMapConfig.xml
at org.apache.ibatis.io.Resources.getResourceAsStream(Resources.java:114)
at org.apache.ibatis.io.Resources.getResourceAsStream(Resources.java:100)
at App.init(App.java:31)
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.RunBefores.evaluate(RunBefores.java:24)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
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$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$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)
這個應該是idea的問題，重啟之后可以找到文件
java.lang.NullPointerException
at App.findAccounts(App.java:52)
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.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
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$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$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)
原因：是因為accountDao接口沒有生成代理對象
org.apache.ibatis.exceptions.PersistenceException:
### Error querying database. Cause: org.apache.ibatis.executor.ExecutorException: No constructor found in com.itheima.entity.User matching [java.lang.Integer, java.lang.String, java.sql.Timestamp, java.lang.String, java.lang.String, java.lang.Integer, java.lang.String, java.lang.String]
### The error may exist in com/itheima/dao/IUserDao.xml
### The error may involve com.itheima.dao.IUserDao.findAllUser
### The error occurred while handling results
### SQL: SELECT u.*,r.ID role_id,r.ROLE_NAME ,r.ROLE_DESC FROM user u INNER JOIN user_role ur INNER JOIN role r on u.id = ur.UID AND ur.RID = r.ID
### Cause: org.apache.ibatis.executor.ExecutorException: No constructor found in com.itheima.entity.User matching [java.lang.Integer, java.lang.String, java.sql.Timestamp, java.lang.String, java.lang.String, java.lang.Integer, java.lang.String, java.lang.String]
原因：就是因為實體類User里面的有參構造器覆蓋了默認的無參構造器，所以無法封裝。
解決：添加無參構造器，或者把所有有參構造器去掉。
后面框架一般都用無參構造器來封裝，所以實體類可以不用給構造器，如果要給構造器一定要給一個無參的。
log4j:WARN No appenders could be found for logger (org.apache.ibatis.logging.LogFactory).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
重啟idea后正常（原因不明）
org.apache.ibatis.binding.BindingException: Type interface com.itheima.dao.IRoleDao is not known to the MapperRegistry.
at org.apache.ibatis.binding.MapperRegistry.getMapper(MapperRegistry.java:47)
at org.apache.ibatis.session.Configuration.getMapper(Configuration.java:745)
at org.apache.ibatis.session.defaults.DefaultSqlSession.getMapper(DefaultSqlSession.java:292)
at App.init(App.java:35)
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.RunBefores.evaluate(RunBefores.java:24)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
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$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$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)
原因：沒有在SqlMapConfig.xml中配置<mapper>指定dao的映射文件位置。導致找不到對應的接口
org.apache.ibatis.binding.BindingException: Invalid bound statement (not found): com.davina.dao.IUserDao.findUsers
配置文件路徑命名要用/ 否則目錄層級不對，就報這個錯誤，因為找不到IXxxxDao.xml
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 'user'. Cause: java.lang.ClassNotFoundException: Cannot find class: user
因為沒有用別名，但是<resultMap id="userResultMap" type="com.davina.entity.User">的type用了user。如果沒有取別名就應該用包全名
Caused by: org.apache.ibatis.reflection.ReflectionException: There is no getter for property named 'username' in 'class com.davina.entity
原因配置IUserDao.xml的時候在配置這個條件的時候 AND username = #{user.username} 漏了user.所以提示找不到username
當程序報出找不到SqlMapConfig.xml文件的時候，可以去maven面板檢查該模塊是否存在，不存在則添加，然后再來測試
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 'account'. Cause: java.lang.ClassNotFoundException: Cannot find class: account
沒有起別名的時候IxxxDao.xml文件中配置類型相關的屬性時，要寫類全名，否則找不到
異常
Cause: java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for com.itheima.dao.IAccountDao.
原因在延遲加載配置中 select屬性沒有給出引用的“包名.方法”信息
<script> select * from user where 1=1 <if test="username != null and username != ''">and username=#{username}</if></script>
異常
org.apache.ibatis.binding.BindingException: Invalid bound statement (not found): com.itheima.dao.IUserDao.findById
at org.apache.ibatis.binding.MapperMethod$SqlCommand.<init>(MapperMethod.java:225)
at org.apache.ibatis.binding.MapperMethod.<init>(MapperMethod.java:48)
at org.apache.ibatis.binding.MapperProxy.cachedMapperMethod(MapperProxy.java:65)
at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:58)
at com.sun.proxy.$Proxy11.findById(Unknown Source)
at App.findById(App.java:84)
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.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
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$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$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)
這個原因是我拷貝了一個項目練習注解開發的時候刪掉了resources文件夾下的dao映射文件，所以找不到接口。。。
Caused by: java.lang.IllegalArgumentException: Mapped Statements collection already contains value for com.itheima.dao.IUserDao.findById
這個異常原因就是：xml和注解都映射了同一個方法！去掉其中一個映射即可
Caused by: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: java.lang.IllegalArgumentException: Mapped Statements collection already contains value for com.itheima.dao.IUserDao.findUserById
這個異常是因為改用注解開發一對一延時加載后，target文件夾下仍然有映射文件，所以要clean一下，再運行。
注意：注解開發中，SqlMapConfig.xml也要配置mapper否則會報org.apache.ibatis.binding.BindingException: Type interface com.itheima.dao.IUserDao is not known to the MapperRegistry.
MapperRegistry.相關的錯誤基本都是跟SqlMapConfig.xml中的mapper配置有關
Caused by: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: java.io.IOException: Could not find resource com/itheima/dao/IUserDao.xml
這是因為SqlMapConfig.xml中的mappers配置里仍然用了mapper來配置映射文件，而注解開發中本來就不需要映射文件，所以報映射文件找不到
所以應該把主配置文件SqlMapConfig.xml里mappers標簽改為用package配置方式（這個配置方式適用於xml和注解開發，推薦使用）
### The error may exist in com/davina/dao/IAccountDao.xml
### The error may involve defaultParameterMap
### The error occurred while setting parameters
### SQL: SELECT * FROM account a INNER JOIN user u ON a.id = u.id;
### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'a.id' in 'on clause'
這個錯誤實際上不是在IAccountDao.xml，最后兩句說了原因是SQL找不到id字段，所以要檢查哪里用到這個SQL！
然后在IAccountDao.xml發現了這個SQL
剛剛出現一個奇葩問題，運行一對多延時加載測試的時候，沒有進行延時加載，輸出的結果為：
用戶名：老王
賬戶名：null
用戶名：小二王
賬戶名：null
用戶名：哈哈
賬戶名：null
用戶名：傳智播客
賬戶名：null
用戶名：呵呵
賬戶名：null
用戶名：小馬寶莉
賬戶名：null
即沒有延時效果，並且沒有查到賬戶信息，但是如果斷點調試又可以看到賬戶信息
經檢查發現：在User實體類中：
有成員List<Account> accounts;
而該成員的get方法為getAccouts()即不是標准的方法，因為之前發現單詞拼錯，改了成員變量名，但是get/set方法對應的方法名沒改、
更改后運行正常