javax.el.PropertyNotFoundException: /demo.xhtml @24,55 value=“#{UserBean.favYear3}”: Target Unreachable, identifier 'UserBean' resolved to null [duplicate]

问题

I want to have a list box in JSF. I have written a simple code but it does not work. In demo page I see an empty box with out list and in user page I have error.

UserBean.java

@ManagedBean
@SessionScoped   
public class UserBean implements Serializable{
    public String favYear3;//list box

    public String getFavYear3() {
        return favYear3;
    }

    public void setFavYear3(String favYear3) {
        this.favYear3 = favYear3;
    }
    public static class Year{
        public String yearLabel;
        public String yearValue;

        public Year(String yearLabel, String yearValue){
            this.yearLabel = yearLabel;
            this.yearValue = yearValue;
        }

        public String getYearLabel(){
            return yearLabel;
        }

        public String getYearValue(){
            return yearValue;
        }

    }

    public Year[] year3List;

    public Year[] getFavYear3Value() {

        year3List = new Year[3];
        year3List[0] = new Year("Year3 - 2000", "2000");
        year3List[1] = new Year("Year3 - 2010", "2010");
        year3List[2] = new Year("Year3 - 2020", "2020");

        return year3List;
    }

}

demo.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:h="http://java.sun.com/jsf/html"
xmlns:f="http://java.sun.com/jsf/core">
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <title>first jsf page</title>
</head>
<h:body>
    <h1>JSF 2 check example</h1>

    <h:form>
        <h:selectOneListbox value="#{UserBean.favYear3}">
            <f:selectItems value="#{UserBean.favYear3Value}" var="y"
                itemLabel="#{y.yearLabel}" itemValue="#{y.yearValue}" />
        </h:selectOneListbox>
    </h:form>

</h:body>
</html>

user.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:h="http://java.sun.com/jsf/html">
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>second jsf page</title>
</head>
<h:body>
    <h:outputText value="#{UserBean.favYear3}"/>
</h:body>
</html>

My problem: in demo page I have an empty box. in user page the error is:

type Exception report

message 

description The server encountered an internal error () that prevented it from fulfilling this request.

exception 

javax.servlet.ServletException: javax.el.PropertyNotFoundException: /demo.xhtml @24,55 value="#{UserBean.favYear3}": Target Unreachable, identifier 'UserBean' resolved to null
    javax.faces.webapp.FacesServlet.service(FacesServlet.java:321)


root cause 

javax.faces.component.UpdateModelException: javax.el.PropertyNotFoundException: /demo.xhtml @24,55 value="#{UserBean.favYear3}": Target Unreachable, identifier 'UserBean' resolved to null
    javax.faces.component.UIInput.updateModel(UIInput.java:848)
    javax.faces.component.UIInput.processUpdates(UIInput.java:730)
    javax.faces.component.UIForm.processUpdates(UIForm.java:268)
    javax.faces.component.UIComponentBase.processUpdates(UIComponentBase.java:1109)
    javax.faces.component.UIComponentBase.processUpdates(UIComponentBase.java:1109)
    javax.faces.component.UIViewRoot.processUpdates(UIViewRoot.java:1218)
    com.sun.faces.lifecycle.UpdateModelValuesPhase.execute(UpdateModelValuesPhase.java:74)
    com.sun.faces.lifecycle.Phase.doPhase(Phase.java:97)
    com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:114)
    javax.faces.webapp.FacesServlet.service(FacesServlet.java:308)

What is wrong?

回答1:

You have to make your bean reachable/managed. For this, you can either

annotate it with a CDI (@Named) or a JSF (@ManagedBean) annotation:

@Named
@SessionScoped
public class UserBean implements Serializable{...}

or describe it in the faces-config.xml as a managed-bean like this:

<managed-bean>
  <managed-bean-name>userBean</managed-bean-name>
  <managed-bean-class>com.example.UserBean</managed-bean-class>
  <managed-bean-scope>session</managed-bean-scope>
</managed-bean>

回答2:

Your managed bean name in EL is wrong. You've declared the bean as follows:

@ManagedBean
@SessionScoped   
public class UserBean implements Serializable{

When you don't specify the name attribute of the @ManagedBean, then it will conform the Javabeans Naming Conventions default to the classname with 1st character lowercased like so userBean, but yet you're trying to reference them with the exact classname #{UserBean}. You need to fix this name accordingly as #{userBean}.

The faces-config.xml registration is unnecessary for JSF 2.x. Remove it.

来源：https://stackoverflow.com/questions/11009974/javax-el-propertynotfoundexception-demo-xhtml-24-55-value-userbean-favyear

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