Caused by: org.xml.sax.SAXParseException: The content of elements must consist of well-formed charac

启动tomcat后，console报错如下：
Caused by: org.xml.sax.SAXParseException: The content of elements must consist of well-formed character data or markup.
由于这种错误都犯了几次，现在把问题记录下来。
第一种产生的原因是：sql中的大于号（>)或（<)小于号没有进行转义。
XML只有5个转义符:<，>，&，”，©;的转义字符分别如下： < >& " '

第二种产生的原因是：id值重复，原因很可能是你复制一个select时候，忘记更改id值或者复制多了。

第三种产生的原因是：sql代码书写错误。可能原因是：在plsql中用常量执行正常，但是换成变量的时候可能少个括号或者逗号之类的。

第四种产生的原因是：更改后的sql文件没有及时编译到classes目录，具体原因不知。解决办法是：project-clean。如果这样还是没有编译进去，再试试如图所示（清理tomcat临时目录）：

附赠详细报错信息：

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'oldsqlSessionFactory' defined in class path resource [resources/datasouce/datasource.xml]: Invocation of init method failed; nested exception is org.springframework.core.NestedIOException: Failed to parse mapping resource: 'file [E:\develop_tools\apache-tomcat-7.0.59\webapps\bookService\WEB-INF\classes\resources\mybatis\old\GroupRelateMapper.xml]'; nested exception is org.apache.ibatis.builder.BuilderException: Error creating document instance.  Cause: org.xml.sax.SAXParseException: The content of elements must consist of well-formed character data or markup.
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1455)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:294)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:225)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:291)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:567)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:913)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:464)
    at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:385)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:284)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:111)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:5016)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5524)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1575)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1565)
    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
    at java.util.concurrent.FutureTask.run(FutureTask.java:138)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
    at java.lang.Thread.run(Thread.java:662)
Caused by: org.springframework.core.NestedIOException: Failed to parse mapping resource: 'file [E:\develop_tools\apache-tomcat-7.0.59\webapps\bookService\WEB-INF\classes\resources\mybatis\old\GroupRelateMapper.xml]'; nested exception is org.apache.ibatis.builder.BuilderException: Error creating document instance.  Cause: org.xml.sax.SAXParseException: The content of elements must consist of well-formed character data or markup.
    at org.mybatis.spring.SqlSessionFactoryBean.buildSqlSessionFactory(SqlSessionFactoryBean.java:466)
    at org.mybatis.spring.SqlSessionFactoryBean.afterPropertiesSet(SqlSessionFactoryBean.java:340)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1514)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1452)
    ... 22 more
Caused by: org.apache.ibatis.builder.BuilderException: Error creating document instance.  Cause: org.xml.sax.SAXParseException: The content of elements must consist of well-formed character data or markup.
    at org.apache.ibatis.parsing.XPathParser.createDocument(XPathParser.java:253)
    at org.apache.ibatis.parsing.XPathParser.<init>(XPathParser.java:122)
    at org.apache.ibatis.builder.xml.XMLMapperBuilder.<init>(XMLMapperBuilder.java:75)
    at org.mybatis.spring.SqlSessionFactoryBean.buildSqlSessionFactory(SqlSessionFactoryBean.java:462)
    ... 25 more
Caused by: org.xml.sax.SAXParseException: The content of elements must consist of well-formed character data or markup.
    at org.apache.xerces.util.ErrorHandlerWrapper.createSAXParseException(Unknown Source)
    at org.apache.xerces.util.ErrorHandlerWrapper.fatalError(Unknown Source)
    at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
    at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
    at org.apache.xerces.impl.XMLScanner.reportFatalError(Unknown Source)
    at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl$FragmentContentDispatcher.dispatch(Unknown Source)
    at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
    at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
    at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
    at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
    at org.apache.xerces.parsers.DOMParser.parse(Unknown Source)
    at org.apache.xerces.jaxp.DocumentBuilderImpl.parse(Unknown Source)
    at org.apache.ibatis.parsing.XPathParser.createDocument(XPathParser.java:251)
    ... 28 more