Duvida com hibernate

log4j:WARN No appenders could be found for logger (net.sf.hibernate.cfg.Environment).

log4j:WARN Please initialize the log4j system properly.

net.sf.hibernate.MappingException: Error reading resource: hibernate/Amigo.hbm.xml

at net.sf.hibernate.cfg.Configuration.addClass(Configuration.java:336)

at hibernate.AmigoDAO.<init>(AmigoDAO.java:18)

at hibernate.TesteAmigo.main(TesteAmigo.java:31)

Caused by: net.sf.hibernate.MappingException: org.dom4j.DocumentException: <a href="http://hibernate.sourceforge.net">hibernate.sourceforge.net</a> Nested exception: <a href="http://hibernate.sourceforge.net">hibernate.sourceforge.net</a>

at net.sf.hibernate.cfg.Configuration.addInputStream(Configuration.java:293)

at net.sf.hibernate.cfg.Configuration.addClass(Configuration.java:333)

… 2 more

Caused by: org.dom4j.DocumentException: <a href="http://hibernate.sourceforge.net">hibernate.sourceforge.net</a> Nested exception: <a href="http://hibernate.sourceforge.net">hibernate.sourceforge.net</a>

at org.dom4j.io.SAXReader.read(SAXReader.java:358)

at net.sf.hibernate.cfg.Configuration.addInputStream(Configuration.java:283)

… 3 more