mybatis的一些初学者常见错误

最新推荐文章于 2023-06-29 17:11:11 发布

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今天开始学mybatis的时候写了一堆bug。。。。。感觉碰到了特别多的坑
下面就是我今天遇到的bug总结。

一、resultType的类需要加包名

Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException: 
### Error building SqlSession.
### The error may exist in org/sumo/mybatis/PersonMapper.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 'org/sumo/mybatis/PersonMapper.xml'. Cause: org.apache.ibatis.builder.BuilderException: Error resolving class. Cause: org.apache.ibatis.type.TypeException: Could not resolve type alias 'Person'.  Cause: java.lang.ClassNotFoundException: Cannot find class: Person
	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 org.sumo.mybatis.TestMyBatis.main(TestMyBatis.java:16)
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 'org/sumo/mybatis/PersonMapper.xml'. Cause: org.apache.ibatis.builder.BuilderException: Error resolving class. Cause: org.apache.ibatis.type.TypeException: Could not resolve type alias 'Person'.  Cause: java.lang.ClassNotFoundException: Cannot find class: Person
	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)
	... 2 more
Caused by: org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'org/sumo/mybatis/PersonMapper.xml'. Cause: org.apache.ibatis.builder.BuilderException: Error resolving class. Cause: org.apache.ibatis.type.TypeException: Could not resolve type alias 'Person'.  Cause: java.lang.ClassNotFoundException: Cannot find class: Person
	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.xml.XMLConfigBuilder.mapperElement(XMLConfigBuilder.java:373)
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:119)
	... 4 more
Caused by: org.apache.ibatis.builder.BuilderException: Error resolving class. Cause: org.apache.ibatis.type.TypeException: Could not resolve type alias 'Person'.  Cause: java.lang.ClassNotFoundException: Cannot find class: Person
	at org.apache.ibatis.builder.BaseBuilder.resolveClass(BaseBuilder.java:118)
	at org.apache.ibatis.builder.xml.XMLStatementBuilder.parseStatementNode(XMLStatementBuilder.java:74)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.buildStatementFromContext(XMLMapperBuilder.java:135)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.buildStatementFromContext(XMLMapperBuilder.java:128)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:118)
	... 7 more
Caused by: org.apache.ibatis.type.TypeException: Could not resolve type alias 'Person'.  Cause: java.lang.ClassNotFoundException: Cannot find class: Person
	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)
	... 11 more
Caused by: java.lang.ClassNotFoundException: Cannot find class: Person
	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)
	... 13 more

这个错误是因为我的Person类没有加包名

错误示例：
<select id="queryPersonById" resultType="Person" parameterType="int">
		select * from person where id = #{id}
</select>
正确示例：
<select id="queryPersonById" resultType="org.sumo.mybatis.Person" parameterType="int">
		select * from person where id = #{id}
</select>

二、mapper里面的namespace里面可能没加包名或者拼写错误

Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for org.sumo.mybatis.PersonMapper.queryPersonById
### Cause: java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for org.sumo.mybatis.PersonMapper.queryPersonById
	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:150)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:77)
	at org.sumo.mybatis.TestMyBatis.main(TestMyBatis.java:22)
Caused by: java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for org.sumo.mybatis.PersonMapper.queryPersonById
	at org.apache.ibatis.session.Configuration$StrictMap.get(Configuration.java:888)
	at org.apache.ibatis.session.Configuration.getMappedStatement(Configuration.java:721)
	at org.apache.ibatis.session.Configuration.getMappedStatement(Configuration.java:714)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:147)
	... 3 more

错误示例：
<mapper namespace="PersonMapper">
正确示例：
<mapper namespace="org.sumo.mybatis.PersonMapper">

这个mapper有可能会拼错了，比如少了个p PersonMaper。

三、config里面的property参数配置错误

Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: java.sql.SQLException: Error setting driver on UnpooledDataSource. Cause: java.lang.ClassNotFoundException: Cannot find class: ${com.mysql.jdbc.Driver}
### The error may exist in org/sumo/mybatis/PersonMapper.xml
### The error may involve org.sumo.mybatis.PersonMapper.queryPersonById
### The error occurred while executing a query
### Cause: java.sql.SQLException: Error setting driver on UnpooledDataSource. Cause: java.lang.ClassNotFoundException: Cannot find class: ${com.mysql.jdbc.Driver}
	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:150)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:77)
	at org.sumo.mybatis.TestMyBatis.main(TestMyBatis.java:22)
Caused by: java.sql.SQLException: Error setting driver on UnpooledDataSource. Cause: java.lang.ClassNotFoundException: Cannot find class: ${com.mysql.jdbc.Driver}
	at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.initializeDriver(UnpooledDataSource.java:221)
	at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:200)
	at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:196)
	at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.getConnection(UnpooledDataSource.java:93)
	at org.apache.ibatis.datasource.pooled.PooledDataSource.popConnection(PooledDataSource.java:404)
	at org.apache.ibatis.datasource.pooled.PooledDataSource.getConnection(PooledDataSource.java:90)
	at org.apache.ibatis.transaction.jdbc.JdbcTransaction.openConnection(JdbcTransaction.java:139)
	at org.apache.ibatis.transaction.jdbc.JdbcTransaction.getConnection(JdbcTransaction.java:61)
	at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:338)
	at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:84)
	at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:62)
	at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:326)
	at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:83)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148)
	... 3 more

错误示例：
<property name="driver" value="${com.mysql.jdbc.Driver}"/>
正确示例：
<property name="driver" value="com.mysql.jdbc.Driver"/>

开始我是直接从mybatis文档里面直接复制过来的，，没有吧${ }这东西删掉。

四、statement里的句子有问题

Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for org/sumo/mybatis/PersonMapper.queryPersonById
### Cause: java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for org/sumo/mybatis/PersonMapper.queryPersonById
	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:150)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:77)
	at org.sumo.mybatis.TestMyBatis.main(TestMyBatis.java:22)
Caused by: java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for org/sumo/mybatis/PersonMapper.queryPersonById
	at org.apache.ibatis.session.Configuration$StrictMap.get(Configuration.java:888)
	at org.apache.ibatis.session.Configuration.getMappedStatement(Configuration.java:721)
	at org.apache.ibatis.session.Configuration.getMappedStatement(Configuration.java:714)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:147)
	... 3 more

错误示例：
String statement="org/sumo/mybatis/PersonMapper.queryPersonById";
正确示例：
String statement="org.sumo.mybatis.PersonMapper.queryPersonById";

我开始用的是" / "。。。

四、数据库jar包版本问题

还可能出现数据库跟mybatis不匹配的情况，这个时候可能也需要换个高点或者低点的版本试下。

Oracle可能会出现这个问题，我用mysql好像没有这种问题。