急 hibernate总是报错 求大神指导
刚开始学hibernate

错误信息
log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment).
log4j:WARN Please initialize the log4j system properly.
Exception in thread "main" java.lang.ExceptionInInitializerError
at cn.hongle.hibernate.Many2Many.add(Many2Many.java:47)
at cn.hongle.hibernate.Many2Many.main(Many2Many.java:14)
Caused by: org.hibernate.InvalidMappingException: Could not parse mapping document from resource cn/hongle/domain/Student.hbm.xml
at org.hibernate.cfg.Configuration.addResource(Configuration.java:569)
at org.hibernate.cfg.Configuration.parseMappingElement(Configuration.java:1587)
at org.hibernate.cfg.Configuration.parseSessionFactory(Configuration.java:1555)
at org.hibernate.cfg.Configuration.doConfigure(Configuration.java:1534)
at org.hibernate.cfg.Configuration.doConfigure(Configuration.java:1508)
at org.hibernate.cfg.Configuration.configure(Configuration.java:1428)
at org.hibernate.cfg.Configuration.configure(Configuration.java:1414)
at cn.hongle.hibernate.HibernateUtils.<clinit>(HibernateUtils.java:17)
... 2 more
Caused by: org.hibernate.InvalidMappingException: Could not parse mapping document from invalid mapping
at org.hibernate.cfg.Configuration.addInputStream(Configuration.java:502)
at org.hibernate.cfg.Configuration.addResource(Configuration.java:566)
... 9 more
Caused by: org.xml.sax.SAXParseException; lineNumber: 13; columnNumber: 48; Element type "Set" must be declared.
at org.apache.xerces.util.ErrorHandlerWrapper.createSAXParseException(Unknown Source)
at org.apache.xerces.util.ErrorHandlerWrapper.error(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.dtd.XMLDTDValidator.handleStartElement(Unknown Source)
at org.apache.xerces.impl.dtd.XMLDTDValidator.startElement(Unknown Source)
at org.apache.xerces.impl.XMLNSDocumentScannerImpl.scanStartElement(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.AbstractSAXParser.parse(Unknown Source)
at org.dom4j.io.SAXReader.read(SAXReader.java:465)
at org.hibernate.cfg.Configuration.addInputStream(Configuration.java:499)
... 10 more



hibernate.cfg.xml:


<?xml version="1.0"?>
<!DOCTYPE hiber