Java EE 6：目标无法访问，标识符'helloBean'已解析为null [英] Java EE 6: Target Unreachable, identifier 'helloBean' resolved to null
问题描述
我正在尝试使用一个简单的JSF 2教程示例。
I am trying to get a simple JSF 2 tutorial example to work.
我在Eclipse中使用动态Web项目并发布到Glassfish 3服务器（运行 - >在服务器上运行）。第一个index.xhtml页面正确加载，但是当我必须访问托管bean时，会显示以下错误：
I am using the dynamic web project in Eclipse and publishing to a Glassfish 3 server (run -> run on server). The first index.xhtml page loads correctly, but when I have to access a managed bean, the following error displays:
/index.xhtml @14,48 value="#{helloBean.name}": Target Unreachable, identifier 'helloBean' resolved to null
我已经看过关于这个主题的各种其他讨论，但是这些解决方案对我来说似乎不起作用（例如，添加beans.xml，根据命名约定给托管bean命名等）。
I've had a look at the various other discussions on this topic, however the solutions never seem to work for me (e.g. adding beans.xml, giving the managed bean a name etc, following naming conventions).
任何帮助都将不胜感激。
Any help would be appreciated.
以下是我目前正在使用的代码：
Here is the code I am currently working with:
Index.xhtml
Index.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>JSF 2.0 Hello World</title>
</h:head>
<h:body>
<h3>JSF 2.0 Hello World Example - hello.xhtml</h3>
<h:form>
<h:inputText value="#{helloBean.name}"></h:inputText>
<h:commandButton value="Welcome Me" action="response"></h:commandButton>
</h:form>
</h:body>
</html>
response.xhtml：
response.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">
<h:head>
<title>JSF 2.0 Hello World</title>
</h:head>
<h:body bgcolor="white">
<h3>JSF 2.0 Hello World Example - welcome.xhtml</h3>
<h4>Welcome #{helloBean.name}</h4>
</h:body>
</html>
管理豆：
package java.hello1;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;
import java.io.Serializable;
@ManagedBean
@SessionScoped
public class HelloBean implements Serializable {
private static final long serialVersionUID = 1L;
private String name = "Ricardo";
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
web.xml：
<?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"
id="WebApp_ID" version="2.5">
<display-name>JavaServerFaces</display-name>
<!-- Change to "Production" when you are ready to deploy -->
<context-param>
<param-name>javax.faces.PROJECT_STAGE</param-name>
<param-value>Development</param-value>
</context-param>
<!-- Welcome page -->
<welcome-file-list>
<welcome-file>faces/index.xhtml</welcome-file>
</welcome-file-list>
<!-- JSF mapping -->
<servlet>
<servlet-name>Faces Servlet</servlet-name>
<servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<!-- Map these files with JSF -->
<servlet-mapping>
<servlet-name>Faces Servlet</servlet-name>
<url-pattern>/faces/*</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>Faces Servlet</servlet-name>
<url-pattern>*.jsf</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>Faces Servlet</servlet-name>
<url-pattern>*.faces</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>Faces Servlet</servlet-name>
<url-pattern>*.xhtml</url-pattern>
</servlet-mapping>
</web-app>
推荐答案
您需要符合JSF 2.0 /WEB-INF/faces-config.xml 文件，以便让JSF解释注释。
You need to have a JSF 2.0 compliant /WEB-INF/faces-config.xml file in order to get JSF to interpret the annotations.
<?xml version="1.0" encoding="UTF-8"?>
<faces-config
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-facesconfig_2_0.xsd"
version="2.0">
<!-- Config here. Can even be kept empty. -->
</faces-config>
如果您已经有一个或者如果没有解决问题，请注意服务器启动如果您没有看到任何警告/错误，请记录日志。
If you already have one or if that doesn't solve the problem, please pay attention to server startup logs if you don't see any warnings/errors.
顺便说一下，您的 /WEB-INF/web.xml 文件声明符合Servlet 2.5规范。虽然这可能不一定有害，但如果您使用符合Servlet 3.0的容器则毫无意义。更新根声明，如下所示：
By the way, your /WEB-INF/web.xml file is declared conform Servlet 2.5 specification. While this may not necessarily harm, it makes no sense if you're using a Servlet 3.0 compliant container. Update the root declaration as follows:
<?xml version="1.0" encoding="UTF-8"?>
<web-app
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
version="3.0">
<!-- Config here. -->
</web-app>
/WEB-INF/beans.xml 用于CDI注释，如 @Named ， @Inject 等等。只需一个完全空的文件即可将其打开。它与JSF注释完全没有关系，如 @ManagedBean ， @ManagedProperty 等等。它也不应该相互混淆/混合。
The /WEB-INF/beans.xml is intented for CDI annotations like @Named, @Inject and so on. Just a completely empty file is sufficient to turn it on. It has totally no relationship to JSF annotations like @ManagedBean, @ManagedProperty and so on. It should also not be confused/mixed with each other.
这篇关于Java EE 6：目标无法访问，标识符'helloBean'已解析为null的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
