目标不可达，标识符“nameWrapper”解析为空]与根源javax.el.PropertyNotFoundException

Question

我是新与JSF，当我检查了我的代码，我一直都想与此异常，当我打开浏览器：

org.apache.catalina.core.StandardWrapperValve invoke 
SEVERE: Servlet.service() for servlet [Faces Servlet] in context with path [/SampleApplication] threw exception [/login.xhtml @11,69 value="#{nameWrapper.name}": Target Unreachable, identifier 'nameWrapper' resolved to null] with root cause 
javax.el.PropertyNotFoundException: Target Unreachable, identifier 'nameWrapper' resolved to null 
    at org.apache.el.parser.AstValue.getTarget(AstValue.java:98) 
    at org.apache.el.parser.AstValue.getType(AstValue.java:82) 
    at org.apache.el.ValueExpressionImpl.getType(ValueExpressionImpl.java:172) 
    at com.sun.faces.facelets.el.TagValueExpression.getType(TagValueExpression.java:98) 
    at com.sun.faces.renderkit.html_basic.HtmlBasicInputRenderer.getConvertedValue(HtmlBasicInputRenderer.java:95) 
    at javax.faces.component.UIInput.getConvertedValue(UIInput.java:1046) 
    at javax.faces.component.UIInput.validate(UIInput.java:976) 
    at javax.faces.component.UIInput.executeValidate(UIInput.java:1249) 
    at javax.faces.component.UIInput.processValidators(UIInput.java:712) 
    at javax.faces.component.UIForm.processValidators(UIForm.java:253) 
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1261) 
    at javax.faces.component.UIViewRoot.processValidators(UIViewRoot.java:1195) 
    at com.sun.faces.lifecycle.ProcessValidationsPhase.execute(ProcessValidationsPhase.java:76) 
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) 
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198) 
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) 
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) 
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222) 
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123) 
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171) 
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100) 
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953) 
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408) 
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1041) 
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:603) 
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312) 
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) 
    at java.lang.Thread.run(Unknown Source) 

这是我的代码：

<h:form> 
    Name: 
    <h:inputText id="text1" value="#{nameWrapper.name}" /> 
    <br /> 
    Address: 
    <h:inputText id="text2" value="#{nameWrapper.address}" /> 
    <br /> 
    Zip: 
    <h:inputText id="text3" value="#{nameWrapper.zip}" /> 
    <br /> 
    <h:commandButton id="submit" value="Submit" action="PageTwo" /> 
</h:form> 

和：

Your password is <h:outputText id="outtext" value="#{nameWrapper.outtext}" />! 

和：

import javax.faces.bean.ManagedBean; 
    import javax.faces.bean.SessionScoped; 

    @ManagedBean 
    @SessionScoped 
    public class NameWrapper { 

     private String name; 
     private String address; 
     private String zip; 
     @SuppressWarnings("unused") 
     private String outtext; 

     public String getName() { 
      return name; 
     } 

     public void setName(String name) { 
      this.name = name; 
     } 

     public String getAddress() { 
      return address; 
     } 

     public void setAddress(String address) { 
      this.address = address; 
     } 

     public String getZip() { 
      return zip; 
     } 

     public void setZip(String zip) { 
      this.zip = zip; 
     } 

     public String getOuttext() { 
      return name + zip + address; 
     } 

     public void setOuttext(String outtext) { 
      this.outtext = outtext; 
     } 

    } 

该代码是从一个教程，我没有弄清楚我做错了什么，我跟着关于这个异常的所有答案，我仍然没有成功解决它谢谢！

Answer 1

您必须使用JSF标准标记（h：head，h：body），我在下面给出了一个示例，并且还在ManagedBean中实现了Serializable。

XHTML

<?xml version="1.0" encoding="UTF-8"?> 
<!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"> 

    <h:head> 
     <title>Test</title> 
    </h:head> 
    <h:body> 
     <h:form> 
      Name: 
      <h:inputText id="text1" value="#{nameWrapper.name}" /> 
      <br /> 
      Address: 
      <h:inputText id="text2" value="#{nameWrapper.address}" /> 
      <br /> 
      Zip: 
      <h:inputText id="text3" value="#{nameWrapper.zip}" /> 
      <br /> 
      <h:commandButton id="submit" value="Submit" action="PageTwo" /> 
     </h:form> 
    </h:body> 
</html> 

ManagedBean

import java.io.Serializable; 
import javax.faces.bean.ManagedBean; 
import javax.faces.bean.SessionScoped; 

@ManagedBean(name = "nameWrapper") 
@SessionScoped 
public class NameWrapper implements Serializable{ 

    private String name; 
    private String address; 
    private String zip; 
    @SuppressWarnings("unused") 
    private String outtext; 

    public String getName() { 
     return name; 
    } 

    public void setName(String name) { 
     this.name = name; 
    } 

    public String getAddress() { 
     return address; 
    } 

    public void setAddress(String address) { 
     this.address = address; 
    } 

    public String getZip() { 
     return zip; 
    } 

    public void setZip(String zip) { 
     this.zip = zip; 
    } 

    public String getOuttext() { 
     return name + zip + address; 
    } 

    public void setOuttext(String outtext) { 
     this.outtext = outtext; 
    } 

} 

PageTwo

<?xml version="1.0" encoding="UTF-8"?> 
<!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"> 

    <h:head> 
     <title>PageTwo</title> 
    </h:head> 
    <h:body> 
     PageTwo 
    </h:body> 
</html>