我现在在学习JSF，我试着做了一个HelloWorld，最简单的那种
运行出错
如下：
type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException: java.lang.NullPointerException
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:522)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:356)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:337)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
com.sun.faces.context.ExternalContextImpl.dispatch(ExternalContextImpl.java:322)
com.sun.faces.application.ViewHandlerImpl.renderView(ViewHandlerImpl.java:142)
com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:87)
com.sun.faces.lifecycle.LifecycleImpl.phase(LifecycleImpl.java:200)
com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:117)
javax.faces.webapp.FacesServlet.service(FacesServlet.java:198)
root cause
java.lang.NullPointerException
org.apache.jsp.pages.index_jsp._jspInit(index_jsp.java:31)
org.apache.jasper.runtime.HttpJspBase.init(HttpJspBase.java:52)
org.apache.jasper.servlet.JspServletWrapper.getServlet(JspServletWrapper.java:159)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:329)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:337)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
com.sun.faces.context.ExternalContextImpl.dispatch(ExternalContextImpl.java:322)
com.sun.faces.application.ViewHandlerImpl.renderView(ViewHandlerImpl.java:142)
com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:87)
com.sun.faces.lifecycle.LifecycleImpl.phase(LifecycleImpl.java:200)
com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:117)
javax.faces.webapp.FacesServlet.service(FacesServlet.java:198)
问题补充：这是我的index页面
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>第一个JSP </title>
</head>
<body>
<f:view>
<h:form>
<h3>请输入名字： </h3>
名称： <h:inputText value="#{user.name}"> </h:inputText>
<h:commandButton value="确定" action="login"> </h:commandButton>
</h:form>
</f:view>
</body>
</html>
这是我的faces-config配置文件：
<faces-config>
<navigation-rule>
<from-view-id>/pages/index.jsp </from-view-id>
<navigation-case>
<from-outcome>login </from-outcome>
<to-view-id>/pages/welcome.jsp </to-view-id>
</navigation-case>
</navigation-rule>
<managed-bean>
<managed-bean-name>user </managed-bean-name>
<managed-bean-class>
cn.javass.faces.UserBean
</managed-bean-class>
<managed-bean-scope>session </managed-bean-scope>