tobago-core/src/main/java/org/apache/myfaces/tobago/context/TobagoExceptionHandler.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.myfaces.tobago.context;

import org.apache.myfaces.tobago.util.WebXmlUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.faces.FacesException;
import javax.faces.application.FacesMessage;
import javax.faces.application.NavigationHandler;
import javax.faces.application.ViewExpiredException;
import javax.faces.application.ViewHandler;
import javax.faces.component.UIViewRoot;
import javax.faces.context.ExceptionHandler;
import javax.faces.context.ExceptionHandlerWrapper;
import javax.faces.context.FacesContext;
import javax.faces.event.AbortProcessingException;
import javax.faces.event.ExceptionQueuedEvent;
import javax.faces.event.ExceptionQueuedEventContext;
import javax.faces.event.PhaseId;
import javax.faces.event.PreRenderViewEvent;
import javax.faces.view.ViewDeclarationLanguage;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.lang.invoke.MethodHandles;
import java.util.Iterator;

public class TobagoExceptionHandler extends ExceptionHandlerWrapper {

  private static final Logger LOG = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());

  public TobagoExceptionHandler(final ExceptionHandler delegate) {
    super(delegate);
  }

  @Override
  public void handle() throws FacesException {

    final FacesContext facesContext = FacesContext.getCurrentInstance();

    if (facesContext.getPartialViewContext().isAjaxRequest()) {
      final Iterator<ExceptionQueuedEvent> events = getUnhandledExceptionQueuedEvents().iterator();
      if (events.hasNext()) {
        final Throwable exception = events.next().getContext().getException();
        if (!(exception instanceof AbortProcessingException)) {
          final String errorPageLocation = WebXmlUtils.getErrorPageLocation(exception);

          if (errorPageLocation != null
              && (facesContext.getCurrentPhaseId() != PhaseId.RENDER_RESPONSE
              || !facesContext.getExternalContext().isResponseCommitted())) {

            try {
              final HttpServletRequest request = (HttpServletRequest) facesContext.getExternalContext().getRequest();
              final HttpServletResponse response =
                  (HttpServletResponse) facesContext.getExternalContext().getResponse();

              request.setAttribute("javax.servlet.error.exception", exception);
              request.setAttribute("javax.servlet.error.exception_type", exception.getClass());
              request.setAttribute("javax.servlet.error.message", exception.getMessage());
              request.setAttribute("javax.servlet.error.request_uri", request.getRequestURI());
              request.setAttribute("javax.servlet.error.status_code", HttpServletResponse.SC_INTERNAL_SERVER_ERROR);

              response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);

              renderErrorPage(facesContext, errorPageLocation);
              cleanupExceptionQueuedEvents();
            } catch (final IOException e) {
              throw new FacesException(e);
            }
          } else {
            LOG.debug("Can't return an error page. errorPageLocation='{}'", errorPageLocation);
          }
        }
      }
    } else {
      final Iterator<ExceptionQueuedEvent> iterator = getUnhandledExceptionQueuedEvents().iterator();
      while (iterator.hasNext()) {
        final ExceptionQueuedEvent event = iterator.next();
        final ExceptionQueuedEventContext context = (ExceptionQueuedEventContext) event.getSource();
        Throwable cause = this.getWrapped().getRootCause(context.getException());
        if (cause == null) {
          cause = context.getException();
        }
        final NavigationHandler nav = facesContext.getApplication().getNavigationHandler();

        if (cause instanceof ViewExpiredException
            || cause != null && cause.getCause() instanceof ViewExpiredException) {
          final ViewExpiredException viewExpiredException = (ViewExpiredException)
              (cause instanceof ViewExpiredException ? cause : cause.getCause());
          try {
            facesContext.addMessage(null,
                new FacesMessage(FacesMessage.SEVERITY_WARN,
                    "The view has been expired!",
                    "Please check the given data or try to start from the beginning."));
            nav.handleNavigation(facesContext, null, viewExpiredException.getViewId());
            facesContext.renderResponse();
            LOG.debug("Handling ViewExpiredException on viewId: {}", viewExpiredException.getViewId());
          } finally {
            iterator.remove();
          }
        } else {
          try {
            final boolean error404 = cause instanceof FileNotFoundException
                || cause != null && cause.getCause() instanceof FileNotFoundException;
            final FacesMessage message;
            if (error404) {
              message = new FacesMessage(FacesMessage.SEVERITY_ERROR,
                  "The page was not found!",
                  "The requested page was not found!");
              facesContext.getExternalContext().setResponseStatus(HttpServletResponse.SC_NOT_FOUND);
              LOG.warn("Handling 404 exception.");
            } else {
              message = new FacesMessage(FacesMessage.SEVERITY_ERROR,
                  "An unknown error has occurred!" + " xxx",
                  "An unknown error has occurred!" + " xxx");
              facesContext.getExternalContext().setResponseStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
              LOG.warn("Handling 500 exception.", cause);
            }
            facesContext.addMessage(null, message);
            final String viewId = "/tobago/error.xhtml";

            // when the rendering was not yet started, we can forward to an error page
            if (event.getContext().getPhaseId().getOrdinal() < PhaseId.RENDER_RESPONSE.getOrdinal()) {
              nav.handleNavigation(facesContext, null, viewId);
              facesContext.renderResponse();
            } else {
              final HttpServletResponse response =
                  (HttpServletResponse) facesContext.getExternalContext().getResponse();
              response.resetBuffer(); // undo rendering, if you can.
              final ViewHandler viewHandler = facesContext.getApplication().getViewHandler();
              final ViewDeclarationLanguage vdl = viewHandler.getViewDeclarationLanguage(facesContext, viewId);
              final UIViewRoot viewRoot = viewHandler.createView(facesContext, viewId);
              vdl.buildView(facesContext, viewRoot);
              facesContext.getApplication().publishEvent(facesContext, PreRenderViewEvent.class, viewRoot);
              vdl.renderView(facesContext, viewRoot);
            }
          } catch (Exception e) {
            LOG.error("Exception while exception handling!", e);
          } finally {
            facesContext.responseComplete();
            iterator.remove();
          }
        }
      }
    }

    super.handle();
  }

  private void renderErrorPage(final FacesContext facesContext, final String errorPageLocation) throws IOException {
    final ViewHandler viewHandler = facesContext.getApplication().getViewHandler();
    final UIViewRoot viewRoot = viewHandler.createView(facesContext, errorPageLocation);
    facesContext.setViewRoot(viewRoot);
    facesContext.getPartialViewContext().setRenderAll(true);

    final ViewDeclarationLanguage viewDeclarationLanguage = viewHandler
        .getViewDeclarationLanguage(facesContext, errorPageLocation);
    viewDeclarationLanguage.buildView(facesContext, viewRoot);
    facesContext.getApplication().publishEvent(facesContext, PreRenderViewEvent.class, viewRoot);
    viewDeclarationLanguage.renderView(facesContext, viewRoot);

    facesContext.responseComplete();
  }

  private void cleanupExceptionQueuedEvents() {
    final Iterator<ExceptionQueuedEvent> exceptionQueuedEvents = getUnhandledExceptionQueuedEvents().iterator();
    while (exceptionQueuedEvents.hasNext()) {
      exceptionQueuedEvents.next();
      exceptionQueuedEvents.remove();
    }
  }

}