Mybatis异常汇总：

Exception in thread "main" java.lang.ExceptionInInitializerError
at mybatis.conn.UserDAOImpl.findUserById(UserDAOImpl.java:24)
at mybatis.conn.TestDAO.main(TestDAO.java:37)
Caused by: org.apache.ibatis.exceptions.PersistenceException:
### Error building SqlSession.
### The error may exist in model/UserMapper.xml
### Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: java.lang.RuntimeException: 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
at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:23)
at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:79)
at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:63)
at mybatis.conn.MybatisUitl.<clinit>(MybatisUitl.java:25)
... 2 more
Caused by: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: java.lang.RuntimeException: 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
at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:105)
at org.apache.ibatis.builder.xml.XMLConfigBuilder.parse(XMLConfigBuilder.java:88)
at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:77)
... 4 more
Caused by: java.lang.RuntimeException: 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
at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:113)
at org.apache.ibatis.builder.xml.XMLMapperBuilder.parse(XMLMapperBuilder.java:88)
at org.apache.ibatis.builder.xml.XMLConfigBuilder.mapperElement(XMLConfigBuilder.java:311)
at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:103)
... 6 more
Caused by: 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
at org.apache.ibatis.builder.BaseBuilder.resolveClass(BaseBuilder.java:94)
at org.apache.ibatis.builder.xml.XMLStatementBuilder.parseStatementNode(XMLStatementBuilder.java:83)
at org.apache.ibatis.builder.xml.XMLMapperBuilder.buildStatementFromContext(XMLMapperBuilder.java:128)
at org.apache.ibatis.builder.xml.XMLMapperBuilder.buildStatementFromContext(XMLMapperBuilder.java:121)
at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:111)
... 9 more
Caused by: org.apache.ibatis.type.TypeException: Could not resolve type alias 'User'.  Cause: java.lang.ClassNotFoundException: Cannot find class: User
at org.apache.ibatis.type.TypeAliasRegistry.resolveAlias(TypeAliasRegistry.java:109)
at org.apache.ibatis.builder.BaseBuilder.resolveAlias(BaseBuilder.java:115)
at org.apache.ibatis.builder.BaseBuilder.resolveClass(BaseBuilder.java:92)
... 13 more
Caused by: java.lang.ClassNotFoundException: Cannot find class: User
at org.apache.ibatis.io.ClassLoaderWrapper.classForName(ClassLoaderWrapper.java:188)
at org.apache.ibatis.io.ClassLoaderWrapper.classForName(ClassLoaderWrapper.java:87)
at org.apache.ibatis.io.Resources.classForName(Resources.java:250)
at org.apache.ibatis.type.TypeAliasRegistry.resolveAlias(TypeAliasRegistry.java:105)
... 15 more
解决办法在mybatis-config.xml中添加

<typeAliases>
		<typeAlias alias="user" type="model.User"/>
	</typeAliases>"

2
Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException:
### Error querying database.  Cause: java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for model.UserMapper.findUserById
### Cause: java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for model.UserMapper.findUserById
at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:23)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:104)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:95)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:59)
at mybatis.conn.UserDAOImpl.findUserById(UserDAOImpl.java:28)
at mybatis.conn.TestDAO.main(TestDAO.java:37)
Caused by: java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for model.UserMapper.findUserById
at org.apache.ibatis.session.Configuration$StrictMap.get(Configuration.java:672)
at org.apache.ibatis.session.Configuration.getMappedStatement(Configuration.java:507)
at org.apache.ibatis.session.Configuration.getMappedStatement(Configuration.java:500)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:100)
... 4 more
解决方法

List userList = session.selectOne(
						[color=red]model.UserMapper[/color].findUserById", 3);

<mapper namespace="[color=red]model.UserMapper[/color]">
  <select id="findUserById" parameterType="int" resultType="User">

UserMapper.xml的namespace和调用类中的函数设定值相同。