运行一个简单的JSF应用程序时出现错误

当我试图运行一个基本的JSF应用程序时，我得到以下异常。我使用JSF1.1, JDK 6和tomcat 6.0.18。

异常

description The server encountered an internal error () that prevented it from fulfilling this request.
exception 
javax.servlet.ServletException: Error testing property 'lastname' in bean of type null
    javax.faces.webapp.FacesServlet.service(FacesServlet.java:209)

root cause 
javax.faces.el.PropertyNotFoundException: Error testing property 'lastname' in bean of type null
    com.sun.faces.el.PropertyResolverImpl.getType(PropertyResolverImpl.java:342)
    com.sun.faces.el.impl.ArraySuffix.getType(ArraySuffix.java:240)
    com.sun.faces.el.impl.ComplexValue.getType(ComplexValue.java:208)
    com.sun.faces.el.ValueBindingImpl.getType(ValueBindingImpl.java:345)
    com.sun.faces.renderkit.html_basic.HtmlBasicInputRenderer.getConvertedValue(HtmlBasicInputRenderer.java:111)
    javax.faces.component.UIInput.getConvertedValue(UIInput.java:713)
    javax.faces.component.UIInput.validate(UIInput.java:638)
    javax.faces.component.UIInput.executeValidate(UIInput.java:849)
    javax.faces.component.UIInput.processValidators(UIInput.java:412)
    javax.faces.component.UIForm.processValidators(UIForm.java:170)
    javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:912)
    javax.faces.component.UIViewRoot.processValidators(UIViewRoot.java:342)
    com.sun.faces.lifecycle.ProcessValidationsPhase.execute(ProcessValidationsPhase.java:78)
    com.sun.faces.lifecycle.LifecycleImpl.phase(LifecycleImpl.java:200)
    com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:90)
    javax.faces.webapp.FacesServlet.service(FacesServlet.java:197)

下面是我创建的相同的文件:

//jsfmbean.jsp

<!DOCTYPE HTML PUBLIC
"-//W3C//DTD HTML 4.01 Transitional//EN">
    <%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %>
    <%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %>
<f:view>
<html>
<body bgcolor="cyan">
<h:form id="form1" >
<h:inputText id="text1" value="#{text2}" />
<h:inputText id="text2" value="#{player.lastname}" />
 <h:commandButton action="success" value="success" />
 <h:commandButton action="#{player.changeName}" value="failure" />
 </h:form>
</body>
</html>
</f:view>

//faces-config.xml

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE faces-config PUBLIC
  "-//Sun Microsystems, Inc.//DTD JavaServer Faces Config 1.1//EN"
  "http://java.sun.com/dtd/web-facesconfig_1_1.dtd">

<faces-config>
  <application>
  <locale-config>
  <default-locale>en</default-locale>  
  </locale-config>
  </application>
  <navigation-rule> 

  <from-view-id> 
   /jsfevent.jsp 
  </from-view-id> 
  <navigation-case>
  <from-outcome>success</from-outcome> 
  <to-view-id>/mathew.jsp</to-view-id> 
   </navigation-case> 
   <navigation-case> 
   <from-outcome>failure</from-outcome> 
   <to-view-id>/amy.jsp</to-view-id> 
   </navigation-case> 
  </navigation-rule> 

  <navigation-rule> 
<from-view-id>/jsfmbean.jsp</from-view-id> 
<navigation-case> 
<from-outcome>success</from-outcome> 
<to-view-id>/mathew.jsp</to-view-id> 
</navigation-case> 
</navigation-rule> 
<managed-bean> 
<managed-bean-name>player</managed-bean-name> 
<managed-bean-class> 
ourdemo.player 
</managed-bean-class> 
<managed-bean-scope> 
session 
</managed-bean-scope> 
<managed-property> 
<property-name>firstname</property-name> 
<property-type>java.lang.String</property-type>
<value>Mahatma</value> 
</managed-property> 
<managed-property> 
<property-name>lastname</property-name> 
<property-type>java.lang.String</property-type>
<value>Gandhiji</value> 
</managed-property> 
</managed-bean>
</faces-config>

//Player.java

package ourdemo; 
import javax.faces.context.*; 
import javax.faces.component.*; 
import javax.faces.validator.*; 
public class Player 
{ 
String firstname ;  
String lastname ; 

public void setFirstname(String a) 
{ 
firstname=a; 
} 
public String getFirstname() 
{ 
return firstname; 
} 
//---------- 
public void setLastname(String b) 
{ 
lastname=b; 
} 
public String  getLastname() 
{ 
return lastname; 
} 
//-------------------
public void changeName() 
{ 
lastname= firstname+" "+lastname; 
}

}

#{player}指向的bean没有正确初始化，因此#{player.lastname}抛出NullPointerException

Java区分大小写。您已经创建了一个具有完整限定类名ourdemo.Player的托管bean，但是您将faces-config.xml中的bean声明为ourdemo.player(注意小写的p而不是大写的P)。这样，JSF就不能找到并创建bean类，这就导致#{player}是null，从而导致这个异常。

修改如下:

<managed-bean>
    <managed-bean-name>player</managed-bean-name> 
    <managed-bean-class>ourdemo.Player</managed-bean-class> 
    <managed-bean-scope>session</managed-bean-scope>
</managed-bean>

与具体问题无关:我完全同意Arjan Tijms在问题评论中的观点:尽可能使用JSF 2.0或更新的版本。JSF 1.1已经过时5年多了，而且有很多缺点。如果由于业务限制而使用JSF 1.1，请说服您的经理。或者，如果您正在使用JSF 1.1是因为您正在阅读过时的书籍/教程，请将它们丢弃，并阅读合适的书籍/教程。

你的faces-config.xml是错误的。

类名声明必须与

相同

<managed-bean-class> 
ourdemo.Player 
</managed-bean-class>

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