从Servlet访问JSF ManagedBean [英] Accessing a JSF managedBean from a Servlet

问题描述

我需要知道从Servlet访问JSF受管Bean(定义为具有应用程序范围)的最佳方法是什么. 目前，我的servlet中有类似的内容:

I need to know what's the best method for accessing a JSF managedBean (which is defined having application scope) from a servlet. Currently I have something like this in my servlet:

  MyApplicationScopeBean bean = null;
  try {
   FacesContext fContext = FacesUtil.getFacesContext(req, resp);
   ServletContext sc = (ServletContext) fContext.getExternalContext().getContext();
   bean = (MyApplicationScopeBean) sc.getAttribute("myManagedBean");   
  } catch (Exception e) {
   e.printStackTrace();
  }

FacesUtil.java(如 http://balusc.blogspot中所述.com/2006/06/communication-in-jsf.html ):

FacesUtil.java (as described in http://balusc.blogspot.com/2006/06/communication-in-jsf.html):

import javax.faces.FactoryFinder;
import javax.faces.component.UIViewRoot;
import javax.faces.context.FacesContext;
import javax.faces.context.FacesContextFactory;
import javax.faces.lifecycle.Lifecycle;
import javax.faces.lifecycle.LifecycleFactory;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class FacesUtil {
    // Getters -----------------------------------------------------------------------------------
    public static FacesContext getFacesContext(
        HttpServletRequest request, HttpServletResponse response)
    {
        // Get current FacesContext.
        FacesContext facesContext = FacesContext.getCurrentInstance();
        // Check current FacesContext.
        if (facesContext == null) {
            // Create new Lifecycle.
            LifecycleFactory lifecycleFactory = (LifecycleFactory)
                FactoryFinder.getFactory(FactoryFinder.LIFECYCLE_FACTORY); 
            Lifecycle lifecycle = lifecycleFactory.getLifecycle(LifecycleFactory.DEFAULT_LIFECYCLE);
            // Create new FacesContext.
            FacesContextFactory contextFactory  = (FacesContextFactory)
                FactoryFinder.getFactory(FactoryFinder.FACES_CONTEXT_FACTORY);
            facesContext = contextFactory.getFacesContext(
                request.getSession().getServletContext(), request, response, lifecycle);
            // Create new View.
            UIViewRoot view = facesContext.getApplication().getViewHandler().createView(
                facesContext, "");
            facesContext.setViewRoot(view);                
            // Set current FacesContext.
            FacesContextWrapper.setCurrentInstance(facesContext);
        }
        return facesContext;
    }
    // Helpers -----------------------------------------------------------------------------------
    // Wrap the protected FacesContext.setCurrentInstance() in a inner class.
    private static abstract class FacesContextWrapper extends FacesContext {
        protected static void setCurrentInstance(FacesContext facesContext) {
            FacesContext.setCurrentInstance(facesContext);
        }
    }     
}

当尝试从servlet访问Bean时，我总是得到null.
您有什么建议? 我正在Tomcat 6上运行JSF 1.2

感谢您的帮助.

I always get a null when trying to access the bean from the servlet.
What are your suggestions? I'm running JSF 1.2 on Tomcat 6

Thanks for your help.

推荐答案

JSF仅在 getServletContext() 方法.您无需手动围绕它创建整个FacesContext.为此，这只是一项不必要的昂贵工作.

JSF stores application scoped managed beans just in the ServletContext. In servlets, the ServletContext is just available by the inherited getServletContext() method. You don't need to manually create a whole FacesContext around it. That's only an unnecessarily expensive task for this purpose.

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    Bean bean = (Bean) getServletContext().getAttribute("bean");
    // ...
}

如果返回null，则仅表示JSF尚未介入，无法为您自动创建bean(即，调用servlet太早了).然后，您需要自己创建和存储它.如果托管bean名称(属性键)相同，它将由JSF使用.

If it returns null, then it simply means that JSF hasn't kicked in yet to auto-create the bean for you (i.e. the servlet is called too early). You would then need to create and store it yourself. It will be used by JSF if the managed bean name (the attribute key) is the same.

    if (bean == null) {
        bean = new Bean();
        getServletContext().setAttribute("bean", bean);
    }

也就是说，这个servlet的目的是什么?您不是试图以错误的方式实现某些功能要求吗?

That said, what's the purpose of this servlet? Aren't you trying to achieve some functional requirement the wrong way?

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