log4j 记录错误日志。

log.error(ex.getMessage(),ex);

2011-06-30 07:14:59,283 [15020576@qtp-26315233-2] ERROR com.test.test1 - / by zero
java.lang.ArithmeticException: / by zero
	at com.test.test1.execute(test1.java:38)
	at com.opensymphony.xwork.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:283)
	at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:166)
	at com.opensymphony.xwork.DefaultActionProxy.execute(DefaultActionProxy.java:116)
	at com.opensymphony.webwork.dispatcher.ServletDispatcher.serviceAction(ServletDispatcher.java:272)
	at com.opensymphony.webwork.dispatcher.ServletDispatcher.service(ServletDispatcher.java:237)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
	at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1221)
	at com.opensymphony.webwork.lifecycle.RequestLifecycleFilter.doFilter(RequestLifecycleFilter.java:67)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
	at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:399)
	at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
	at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
	at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:766)
	at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:450)
	at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
	at org.mortbay.jetty.Server.handle(Server.java:326)
	at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
	at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:928)
	at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:549)
	at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
	at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
	at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:410)
	at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)