jsf jpa JSF教程 - JSF管理Bean

JSF教程 - JSF管理Bean

JSF Managed Bean是使用JSF注册的常规Java Bean类。

JSF Managed Bean是使用JSF注册的常规Java Bean类。...

JSF管理的bean作为UI组件的模型。 它存储使用的数据通过JSF xhtml页面。

在JSF框架的帮助下，Managed Bean可以从JSF页面访问。

在JSF 1.2中，我们必须在JSF配置文件中注册一个托管bean例如faces-config.xml。

从JSF 2.0，可以使用注释注册托管bean。

使用XML配置

以下代码显示如何注册JSF受管Bean

<managed-bean>
  <managed-bean-name>helloWorld</managed-bean-name>
  <managed-bean-class>com..test.HelloWorld</managed-bean-class>
  <managed-bean-scope>request</managed-bean-scope>
</managed-bean> 
<managed-bean>
  <managed-bean-name>message</managed-bean-name>
  <managed-bean-class>com..test.Message</managed-bean-class>
  <managed-bean-scope>request</managed-bean-scope>
</managed-bean>

使用@ManagedBean注释

以下代码显示了如何使用注释注册JSF受管Bean。

@ManagedBean(name = "helloWorld", eager = true)
@RequestScoped
public class HelloWorld {
  
   @ManagedProperty(value="#{message}")
   private Message message;
   ...
}

@ManagedBean 将bean标记为在name属性中指定的名称的托管bean。

如果未指定name属性，则指定受管bean名称将默认为简单类名称，第一个字母为lowercased。 在我们的情况下，它会是helloWorld。

如果eager设置为“true"，那么在请求bean之前创建managed bean。

“lazy"初始化被使用在bean将被创建只有当它被请求。

使用@ManagedBean注释...

范围注释设置受管bean的范围。

如果未指定scope，那么bean将默认为请求作用域。

我们可以将JSF bean范围设置为以下列表。

• @RequestScoped bean lives as long as the HTTP request-response lives. It get created upon a HTTP request and get destroyed when the HTTP response associated with the HTTP request is finished.
• @NoneScoped bean stays as long as a single Expression Language(EL) evaluation. It get created upon an EL evaluation and get destroyed after the EL evaluation.
• @ViewScoped bean lives as long as user is interacting with the same JSF view in the browser window. It gets created upon a HTTP request and gets destroyed when users navigate to a different view.
• @SessionScoped bean lives as long as the HTTP session lives. It gets created upon the first HTTP request and gets destroyed when the HTTP session is invalidated.
• @ApplicationScoped bean lives as long as the web application lives. It gets created upon the first HTTP request or when the web application starts up and the eager=true attribute is set in @ManagedBean and gets destroyed when the web application shuts down.
• @CustomScoped bean lives as long as the bean"s entry in the custom Map which is created for this scope lives.

@ManagedProperty注释

JSF是一个简单的静态依赖注入(DI)框架。@ManagedProperty注释标记要注入到另一个托管bean中的托管bean的属性。