Usar Managed Bean de presentación desde jsp o servlet

Extraido de http://stackoverflow.com/questions/2633112/jsf-get-managed-bean-by-name

In a Servlet, you can get request scoped beans by:

Bean bean = (Bean) request.getAttribute("beanName");

and session scoped beans by:

Bean bean = (Bean) request.getSession().getAttribute("beanName");

and application scoped beans by:

Bean bean = (Bean) getServletContext().getAttribute("beanName");

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If you're running in a dependency injection capable framework/container, it's even more easy:

@Inject
private Bean bean;

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Regardless of the scope, when you're actually inside the FacesContext, then normal JSF2 way is using Application#evaluateExpressionGet():

FacesContext context = FacesContext.getCurrentInstance();
Bean bean = (Bean) context.getApplication().evaluateExpressionGet(context, "#{beanName}", Bean.class);

which can be convenienced as follows:

@SuppressWarnings("unchecked")
public static <T> T findBean(String beanName) {
    FacesContext context = FacesContext.getCurrentInstance();
    return (T) context.getApplication().evaluateExpressionGet(context, "#{" + beanName + "}", Object.class);
}

and can be used as follows:

Bean bean = findBean("bean");

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However, when you're already inside the FacesContext but not inside a dependency injection capable container, then using @ManagedProperty is cleaner since it's more declarative.

@ManagedProperty(value="#{bean}")
private Bean bean;