过滤器中的@Inject不起作用

Question

据我所知，CDI应该在过滤器中工作，但我不能让它为我工作。代码如下所示:

@WebFilter(filterName="authFilter",servletNames={"Faces Servlet"})
public class AuthFilter implements Filter {
    @Inject UserBean userBean;
    public AuthFilter() {
    }
    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        userBean.doSomething(); // Causes NullPointerException
        chain.doFilter(request, response);
    }
}  

UserBean.class

@Stateless
public class UserBean extends JPABean{
// Omitted
}

CDI是启用的，如果我通过initialcontext . dollookup()或Servlet手动进行注入，则注入工作，如下所示:

@WebServlet(name = "MyServlet", urlPatterns = {"/MyPage"})
@ServletSecurity(@HttpConstraint(rolesAllowed={"somerole"}))
public class MyServlet extends HttpServlet {
    @Inject private UserBean userBean;
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        userBean.doStuff(); // Works
        response.sendRedirect(request.getContextPath());
}

CDI在过滤器中不工作吗?既然如此，为什么不呢?如果是这样，我又能做错什么呢?

Answer 1

在本例中，我将CODI @ViewAccessScoped bean (RegisterView)注入过滤器，在bean中设置属性并导航到使用该bean的视图。当页面加载时，我看到用户名设置为"弗雷德"。这也适用于@SessionScoped(但不是@RequestScoped或@ViewScoped)。我认为动态注入是线程安全所必需的，因为在web容器中只有一个过滤器实例，因此所有的实例变量。

要解决的问题是过滤器执行时Faces Servlet没有运行，所以没有FacesContext。getFacesContext()所做的聪明工作是我从2004年的这个博客中直接引用的，我不知道它是谁写的，而且已经有几年没有添加内容了，但是如果有人知道，请告诉我!也许是BalusC穿着他的年轻的时候。它使用静态内部类来访问受保护的FacesServlet#setCurrentInstance()方法。

如果你使用response.sendRedirect()，它将不起作用。

package uk.co.myco.jsfbeans.helper;
import java.io.IOException;
import javax.enterprise.inject.Instance;
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.inject.Inject;
import javax.servlet.DispatcherType;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import uk.co.sportquest.entities.User;
import uk.co.sportquest.general.BaseClass;
import uk.co.sportquest.general.Log;
import uk.co.sportquest.jsfbeans.RegisterView;
/*
 * @author Brendan Healey
 * 
 * http://www.thoughtsabout.net/blog/archives/000033.html
 * 
 */
@WebFilter(filterName = "SocialAuthFilter", urlPatterns = {"/pages/socialAuthFilter.xhtml"},
dispatcherTypes = {DispatcherType.FORWARD, DispatcherType.ERROR, DispatcherType.REQUEST, DispatcherType.INCLUDE})
public class SocialAuthFilter extends BaseClass implements Filter {
    @Inject
    private Instance<RegisterView> rvDynamic;
    private ServletContext servletContext;
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        servletContext = filterConfig.getServletContext();
    }
    @Override
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;
        Log.log("testFilter: " + request.getPathInfo());
        FacesContext ctx = getFacesContext(req, res);
        RegisterView registerView;
        registerView = rvDynamic.get();
        User user = new User();
        user.setUserName("fred");
        registerView.setInputUser(user);
        FacesContext.getCurrentInstance().getExternalContext().redirect("/pages/register.xhtml");
    }
    @Override
    public void destroy() {
    }
    private abstract static class InnerFacesContext extends FacesContext {
        protected static void setFacesContextAsCurrentInstance(FacesContext facesContext) {
            FacesContext.setCurrentInstance(facesContext);
        }
    }
    private FacesContext getFacesContext(ServletRequest request, ServletResponse response) {
        // Try to get it first  
        FacesContext facesContext = FacesContext.getCurrentInstance();
        if (facesContext != null) {
            return facesContext;
        }
        FacesContextFactory contextFactory = (FacesContextFactory) FactoryFinder.getFactory(FactoryFinder.FACES_CONTEXT_FACTORY);
        LifecycleFactory lifecycleFactory = (LifecycleFactory) FactoryFinder.getFactory(FactoryFinder.LIFECYCLE_FACTORY);
        Lifecycle lifecycle = lifecycleFactory.getLifecycle(LifecycleFactory.DEFAULT_LIFECYCLE);
        // Either set a private member servletContext = filterConfig.getServletContext(); 
        // in you filter init() method or set it here like this:
        // ServletContext servletContext = ((HttpServletRequest)request).getSession().getServletContext();
        // Note that the above line would fail if you are using any other protocol than http
        // Doesn't set this instance as the current instance of FacesContext.getCurrentInstance 
        facesContext = contextFactory.getFacesContext(servletContext, request, response, lifecycle);
        // Set using our inner class
        InnerFacesContext.setFacesContextAsCurrentInstance(facesContext);
        // set a new viewRoot, otherwise context.getViewRoot returns null
        UIViewRoot view = facesContext.getApplication().getViewHandler().createView(facesContext, "");
        facesContext.setViewRoot(view);
        return facesContext;
    }
}