mybatis的jar版本问题

用mybatis使用mapper接口开发时报错如下：

Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException: 

### Error building SqlSession.
### Cause: org.apache.ibatis.builder.BuilderException: Error creating document instance.  Cause: org.xml.sax.SAXParseException; lineNumber: 20; columnNumber: 43; 必须为元素类型 "mapper" 声明属性 "class"。
at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:8)
at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:32)
at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:16)
at com.mapper.Test.main(Test.java:17)
Caused by: org.apache.ibatis.builder.BuilderException: Error creating document instance.  Cause: org.xml.sax.SAXParseException; lineNumber: 20; columnNumber: 43; 必须为元素类型 "mapper" 声明属性 "class"。
at org.apache.ibatis.parsing.XPathParser.createDocument(XPathParser.java:238)
at org.apache.ibatis.parsing.XPathParser.<init>(XPathParser.java:102)
at org.apache.ibatis.builder.xml.XMLConfigBuilder.<init>(XMLConfigBuilder.java:40)
at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:29)
... 2 more
Caused by: org.xml.sax.SAXParseException; lineNumber: 20; columnNumber: 43; 必须为元素类型 "mapper" 声明属性 "class"。
at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:203)
at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.error(ErrorHandlerWrapper.java:134)
at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:396)
at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:327)
at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:284)
at com.sun.org.apache.xerces.internal.impl.dtd.XMLDTDValidator.addDTDDefaultAttrsAndValidate(XMLDTDValidator.java:1253)
at com.sun.org.apache.xerces.internal.impl.dtd.XMLDTDValidator.handleStartElement(XMLDTDValidator.java:1917)
at com.sun.org.apache.xerces.internal.impl.dtd.XMLDTDValidator.emptyElement(XMLDTDValidator.java:763)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanStartElement(XMLDocumentFragmentScannerImpl.java:1339)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2784)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:602)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:505)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:841)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:770)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:243)
at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:339)

at org.apache.ibatis.parsing.XPathParser.createDocument(XPathParser.java:236)

... 5 more

一般是jar版本过低或者版本不合适。如我用的是mybatis-3.0.5.jar,报错了。更换为mybatis-3.2.7.jar正常运行。