JSF Managed Bean自动创建？

本文介绍了JSF Managed Bean自动创建？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 29岁程序员，3月因学历无情被辞！ 是否可以自动创建JSF托管bean？Is it possible to have a JSF managed bean be automatically created?例如，我有几个会话范围的bean。有时需要在代码中访问这些实例（而不仅仅是在JSF中），这可以通过以下方式完成：For example I have several session scoped beans. Sometimes it becomes necessary to access these instances in code (rather than just in JSF) this is done by:PageBean pageBean = (PageBean) FacesContext.getCurrentInstance().getExternalContext().getSessionMap().get("pages");但是，如果没有访问过调用＃{pages}的页面，则此解析为null ...无论如何，当范围开始时，JSF是否可以创建一个bean？那么在这种情况下，理想情况下，当用户会话开始时，'pages'bean会立即在会话中实例化吗？However if no page has already been visited which calls to '#{pages}' this resolves to null ... is there anyway to get JSF to create a bean when the scope 'begins'? So in this case ideally when a user session begins the 'pages' bean would be instantiated in the session immediately?推荐答案使用 应用程序＃evaluateExpressionGet（） 。它还会在尚未完成时创建bean。Use Application#evaluateExpressionGet() instead. It will create bean when not done yet.FacesContext context = FacesContext.getCurrentInstance();Bean bean = (Bean) context.getApplication().evaluateExpressionGet(context, "#{bean}", Bean.class);其中bean是托管bean name和 Bean.class 是适当的支持bean类。Where "bean" is the managed bean name and Bean.class is the appropriate backing bean class.如果需要，你可以将它包装在一个帮助器中方法，以便不必进行投射（JSF男孩没有利用泛型和 evaluateExpressionGet 中的 Class 参数） ：You can if necessary wrap this up in a helper method so that casting is unnecessary (the JSF boys didn't take benefit of generics and the Class parameter in evaluateExpressionGet):public static <T> T findBean(String managedBeanName, Class<T> beanClass) { FacesContext context = FacesContext.getCurrentInstance(); return beanClass.cast(context.getApplication().evaluateExpressionGet(context, "#{" + managedBeanName + "}", beanClass));}可以用作：Bean bean = findBean("bean", Bean.class);或者没有类型，但是带有 @SuppressWarnings ：Or without the type, but with a @SuppressWarnings:@SuppressWarnings("unchecked")public static <T> T findBean(String managedBeanName) { FacesContext context = FacesContext.getCurrentInstance(); return (T) context.getApplication().evaluateExpressionGet(context, "#{" + managedBeanName + "}", Object.class);}可以用作：Bean bean = findBean("bean"); 更新：以上是按照JSF 1.2的具体方式。这是JSF 1.1或更早版本的方式，使用当前已弃用的 Application＃createValueBinding（） ：Update: the above is by the way JSF 1.2 specific. Here's the way for JSF 1.1 or older, using the currently deprecated Application#createValueBinding():FacesContext context = FacesContext.getCurrentInstance();Bean bean = (Bean) context.getApplication().createValueBinding("#{bean}").getValue(context); 这篇关于JSF Managed Bean自动创建？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！ 上岸，阿里云！