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从servlet访问jsf managedbean[重复]

javabeans servlets jsf

10

azathoth · 技术社区 · 16 年前

这个问题已经有了答案:

Get JSF managed bean by name in any Servlet related class 6答

我需要知道从servlet访问JSF ManagedBean(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:

  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(如中所述 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);
        }
    }     
}

当试图从servlet访问bean时,我总是得到一个空值。
你有什么建议? 我在Tomcat 6上运行JSF 1.2

谢谢你的帮助。

1 回复 | 直到 16 年前

1

20

BalusC 16 年前

JSF将应用程序范围的托管bean存储在 ServletContext . 在servlets中, 服务上下文 只是被继承的 getServletContext() 方法。您不需要手动创建一个整体 FacesContext 在它周围。为此目的,这只是一项不必要的昂贵任务。

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

如果它回来 null 然后它仅仅意味着JSF还没有开始为您自动创建bean(也就是说servlet被称为太早了)。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,JSF将使用它。

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

也就是说,这个servlet的目的是什么?您是否试图以错误的方式实现某些功能需求?