求帮助JSF问题：org.apache.jasper.JasperException: java.lang.NullPointerException
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>
</managed-bean>
</faces-config>
[解决办法]
帮顶
------解决方案--------------------
<%@ page language="java" contentType="text/html; charset=gb2312"
pageEncoding="gb2312"%>
<%@ taglib prefix="f" uri="http://java.sun.com/jsf/core"%>
<%@ taglib prefix="h" uri="http://java.sun.com/jsf/html"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<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>
[解决办法]
另外，这种方式不那么流行了，现在2.0惯用xhtml格式。
[解决办法]
<?xml version="1.0" encoding="gb2312" ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:f="http://java.sun.com/jsf/core"
xmlns:h="http://java.sun.com/jsf/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>
[解决办法]
注意下web.xml里的配置。给你介绍本书：http://book.51cto.com/art/200812/100238.htm，比较新，还是中文版的，不过只有部分章节。
[解决办法]
上面那段代码是jsp格式的，下面那段是xhtml格式的。
还有你定义和配置了user这个bean吗？
[解决办法]
上面的两种方式我在我的机器上都试验通过，你看看环境吧，比如你的jsf的实现版本，以及web.xml。
[解决办法]
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
version="2.5">
<servlet>
<servlet-name>Faces Servlet</servlet-name>
<servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Faces Servlet</servlet-name>
<url-pattern>*.jsf</url-pattern>
</servlet-mapping>
<context-param>
<param-name>javax.faces.PROJECT_STAGE</param-name>
<param-value>Development</param-value>
</context-param>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
<welcome-file>index.html</welcome-file>
</welcome-file-list>
<context-param>
<param-name>facelets.LIBRARIES</param-name>
<param-value> /WEB-INF/facelets/mycustom.taglib.xml</param-value>
</context-param>
</web-app>
[解决办法]
<html>
<head>
<meta http-equiv="Refresh" content= "0; URL=index.jsf"/>
<title>Start Web Application</title>
</head>
<body>
<p>Please wait for the web application to start.</p>
</body>
</html>
这是index.html。
那个页面定义为index.xhtml。
我的异常网推荐解决方案：The server encountered an internal error () that prevented it from fulfilling this request.,http://www.myexception.cn/java-web/317.html
