使用 CDI（上下文和依赖注入）支持 bean 而不是托管 Bean
[英]Using CDI (Context & Dependency Injection) backing beans instead of Managed Beans
问题描述
I rode that is recommended to use CDI beans as backing beans instead of JSF managed beans.
我认为建议使用 CDI bean 作为支持 bean 而不是 JSF 托管 bean。
So i decided to create a little example, to understand how it works, for a @RequestScopedBean :因此，我决定为@RequestScopedBean创建一个小示例，以了解其工作原理：
-instead of using @ManagedBean("beanName") ,i use @Named("beanName") - 而不是使用@ManagedBean("beanName") ，我使用@Named("beanName")
-instead of using javax.faces.bean.RequestScopped i use javax.enterprise.context.RequestScoped; - 而不是使用javax.faces.bean.RequestScoped我使用javax.enterprise.context.RequestScoped;
The demo program is very simple, i have a field and a submit button, when the user inputs something and the page is refreshed, the inputed value is not displayed anymore(It last while the request lasts right?).演示程序非常简单，我有一个字段和一个提交按钮，当用户输入内容并刷新页面时，输入的值不再显示（它会持续到请求持续对吗？）。 I think i did everything ok, but i get an exception that says:我想我做的一切都很好，但我得到一个例外，上面写着：
WARNING: StandardWrapperValve[Faces Servlet]: PWC1406: Servlet.service() for servlet Faces Servlet threw exception javax.el.PropertyNotFoundException: /index.xhtml @19,47 value="#{cdiBean.passedValue}": Target Unreachable, identifier 'cdiBean' resolved to null
This is how my program looks like:这就是我的程序的样子：
index.xhtml索引.xhtml
<!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:ui="http://java.sun.com/jsf/facelets"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:f="http://java.sun.com/jsf/core">
<h:head>
<title>RequestScope demo CDI(Component Dependency Injection)</title>
</h:head>
<h:body>
<h:form>
<h3>RequestScope demo CDI(Component Dependency Injection)</h3>
<h:inputText value="#{cdiBean.passedValue}"/>
<br/>
<h:commandButton value="submit" action="index"/>
</h:form>
</h:body>
</html>
DemoBB.java演示BB.java
package backingbeans;
import javax.enterprise.context.RequestScoped;
import javax.inject.Named;
@Named("cdiBean")//The Named anotation indicates that this is a CDI bean
@RequestScoped//If we use CDI beans the @RequestScoped annotation must come from: javax.enterprise.context.RequestScoped;
public class DemoBB {
//This value will be saved on the session only until the server responds to the request
private String passedValue;
public String getPassedValue() {
return passedValue;
}
public void setPassedValue(String passedValue) {
this.passedValue = passedValue;
}
}
-Where is my mistake? -我的错误在哪里？
-What is the advantage of using this approach? - 使用这种方法有什么好处？ I still don't understand that.我还是不明白。
1 个解决方案
解决方案1
3 已采纳 2011-07-05 11:25:58
Do you have an empty beans.xml along with your web.xml ?你有一个空的beans.xml和你的web.xml吗？ I think it is mandatory to be there.我认为去那里是必须的。
Read section 15.6 here . 在此处阅读第 15.6 节。 Quote from it:引用它：
CDI doesn't define any special deployment archive.
In an embeddable EJB container, beans may be deployed in any location in which EJBs may be deployed.
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