I got a 404 page, and the error says:

INFO: Initializing log4j from [C:\CS520\workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\csns\WEB-INF\classes\log4j.xml]
log4j:ERROR Could not parse url [file:/C:/CS520/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/csns/WEB-INF/classes/log4j.xml].
java.io.FileNotFoundException: C:\CS520\workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\csns\WEB-INF\classes\log4j.xml (The system cannot find the file specified)
    at java.io.FileInputStream.open(Native Method)
    at java.io.FileInputStream.<init>(Unknown Source)
    at java.io.FileInputStream.<init>(Unknown Source)
    at sun.net.www.protocol.file.FileURLConnection.connect(Unknown Source)
    at sun.net.www.protocol.file.FileURLConnection.getInputStream(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.setupCurrentEntity(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLVersionDetector.determineDocVersion(Unknown Source)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(Unknown Source)
    at javax.xml.parsers.DocumentBuilder.parse(Unknown Source)
    at org.apache.log4j.xml.DOMConfigurator$2.parse(DOMConfigurator.java:690)
    at org.apache.log4j.xml.DOMConfigurator.doConfigure(DOMConfigurator.java:789)
    at org.apache.log4j.xml.DOMConfigurator.doConfigure(DOMConfigurator.java:696)
    at org.apache.log4j.xml.DOMConfigurator.configure(DOMConfigurator.java:821)
    at org.springframework.util.Log4jConfigurer.initLogging(Log4jConfigurer.java:70)
    at org.springframework.web.util.Log4jWebConfigurer.initLogging(Log4jWebConfigurer.java:152)
    at org.springframework.web.util.Log4jConfigListener.contextInitialized(Log4jConfigListener.java:47)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3934)
    at org.apache.catalina.core.StandardContext.start(StandardContext.java:4429)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
    at org.apache.catalina.core.StandardHost.start(StandardHost.java:722)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
    at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)
    at org.apache.catalina.core.StandardService.start(StandardService.java:516)
    at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:583)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)
log4j:WARN No appenders could be found for logger (org.springframework.util.ClassUtils).
log4j:WARN Please initialize the log4j system properly.

SEVERE: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory' defined in ServletContext resource [/WEB-INF/csns-data.xml]: Invocation of init method failed; nested exception is java.io.FileNotFoundException: class path resource [hibernate.cfg.xml] cannot be resolved to URL because it does not exist
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1336)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:471)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409)
    at java.security.AccessController.doPrivileged(Native Method)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:220)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:423)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:729)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:381)
    at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:255)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:199)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:45)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3934)
    at org.apache.catalina.core.StandardContext.start(StandardContext.java:4429)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
    at org.apache.catalina.core.StandardHost.start(StandardHost.java:722)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
    at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)
    at org.apache.catalina.core.StandardService.start(StandardService.java:516)
    at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:583)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)
Caused by: java.io.FileNotFoundException: class path resource [hibernate.cfg.xml] cannot be resolved to URL because it does not exist
    at org.springframework.core.io.ClassPathResource.getURL(ClassPathResource.java:162)
    at org.springframework.orm.hibernate3.LocalSessionFactoryBean.buildSessionFactory(LocalSessionFactoryBean.java:601)
    at org.springframework.orm.hibernate3.AbstractSessionFactoryBean.afterPropertiesSet(AbstractSessionFactoryBean.java:211)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1367)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1333)
    ... 30 more

Where should I look into the probelm?

...workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\csns is where Eclipse deploys and runs the project, and sometimes that folder gets messed up.

In the Servers view, right click on "csns" then select "Clean Module Work Directory ...".

If that doesn't fix the problem, in the Servers view, remove "csns". Exit Eclipse, manually delete the csns folder under ...workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps, then restart Eclipse and try to run the project again.

I got  IllegalArgumentEcxeption after following the instruction above.   I did the refreshing, but it's not helpful.