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Jakarta Faces 3.0+ utility library
There is a newer version: 4.4.1
/*
 * Copyright OmniFaces
 *
 * Licensed 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
 *
 *     https://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.omnifaces.filter;

import static java.lang.String.format;
import static java.util.logging.Level.FINEST;
import static java.util.logging.Level.SEVERE;
import static org.omnifaces.exceptionhandler.FullAjaxExceptionHandler.EXCEPTION_UUID;
import static org.omnifaces.exceptionhandler.FullAjaxExceptionHandler.getExceptionTypesToIgnoreInLogging;
import static org.omnifaces.exceptionhandler.FullAjaxExceptionHandler.getExceptionTypesToUnwrap;
import static org.omnifaces.util.Exceptions.unwrap;
import static org.omnifaces.util.Servlets.getRemoteAddr;
import static org.omnifaces.util.Utils.isOneInstanceOf;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Formatter;
import java.util.Objects;
import java.util.UUID;
import java.util.logging.Logger;

import jakarta.el.ELException;
import jakarta.faces.FacesException;
import jakarta.servlet.FilterChain;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import jakarta.servlet.http.HttpSession;

import org.omnifaces.config.WebXml;
import org.omnifaces.exceptionhandler.FullAjaxExceptionHandler;

/**
 * 
 * The {@link FacesExceptionFilter} will solve 2 problems with exceptions thrown in Faces methods.
 * 

 * Mojarra's FacesFileNotFoundException needs to be interpreted as 404.
 * 
Root cause needs to be unwrapped from {@link FacesException} and {@link ELException} to utilize standard
 * Servlet API error page handling.
 * 
 * 
 * Noted should be that this filter won't run on exceptions thrown during ajax requests. To handle them using
 * web.xml configured error pages, use {@link FullAjaxExceptionHandler}.
 * 

 * Since version 3.2, the {@link FacesExceptionFilter} also logs exceptions with an UUID and IP via the
 * {@link #logException(HttpServletRequest, Throwable, String, String, Object...)} method. The UUID is in turn available
 * in EL by #{requestScope['org.omnifaces.exception_uuid']}.
 *
 * 
Installation
 * 
 * To get it to run, map this filter on an <url-pattern> of /* in web.xml.
 * 
 * <filter>
 *     <filter-name>facesExceptionFilter</filter-name>
 *     <filter-class>org.omnifaces.filter.FacesExceptionFilter</filter-class>
 * </filter>
 * <filter-mapping>
 *     <filter-name>facesExceptionFilter</filter-name>
 *     <url-pattern>/*</url-pattern>
 * </filter-mapping>
 * 
 *
 * Error pages
 * 
 * Please refer the "Error pages" section of the {@link FullAjaxExceptionHandler} javadoc for recommended error page
 * configuration.
 *
 * 
Configuration
 * 
 * Please refer the "Configuration" section of the {@link FullAjaxExceptionHandler} javadoc for available context
 * parameters.
 *
 * 
Customizing FacesExceptionFilter
 * 
 * If more fine grained control is desired for logging the exception, then the developer can opt to extend this
 * {@link FacesExceptionFilter} and override one or more of the following protected methods:
 * 

 * {@link #logException(HttpServletRequest, Throwable, String, String, Object...)}
 * 
 *
 * @author Bauke Scholtz
 * @see FullAjaxExceptionHandler
 * @see HttpFilter
 */
public class FacesExceptionFilter extends HttpFilter {

	private static final Logger logger = Logger.getLogger(FacesExceptionFilter.class.getName());

	private static final String LOG_EXCEPTION_HANDLED =
		"FacesExceptionFilter: An exception occurred during processing servlet request."
			+ " Error page '%s' will be shown.";

	private Class[] exceptionTypesToUnwrap;
	private Class[] exceptionTypesToIgnoreInLogging;

	@Override
	public void init() throws ServletException {
		exceptionTypesToUnwrap = getExceptionTypesToUnwrap(getServletContext());
		exceptionTypesToIgnoreInLogging = getExceptionTypesToIgnoreInLogging(getServletContext());
	}

	@Override
	public void doFilter
		(HttpServletRequest request, HttpServletResponse response, HttpSession session, FilterChain chain)
			throws ServletException, IOException
	{
		try {
			chain.doFilter(request, response);
		}
		catch (FileNotFoundException ignore) {
			logger.log(FINEST, "Ignoring thrown exception; this is a Faces quirk and it should be interpreted as 404.", ignore);
			response.sendError(HttpServletResponse.SC_NOT_FOUND, request.getRequestURI());
		}
		catch (Throwable exception) {
			request.setAttribute(EXCEPTION_UUID, UUID.randomUUID().toString());
			Throwable cause = unwrap(exception instanceof ServletException ? exception.getCause() : exception, exceptionTypesToUnwrap);
			String location = WebXml.instance().findErrorPageLocation(cause);
			logException(request, cause, location, LOG_EXCEPTION_HANDLED, location);

			if (Objects.equals(exception, cause)) {
				throw exception;
			}

			logger.log(FINEST, "Ignoring thrown exception; this is a wrapper exception and only its root cause is of interest.", exception);

			if (cause instanceof RuntimeException) {
				throw (RuntimeException) cause;
			}
			else {
				throw new ServletException(cause);
			}
		}
	}

	/**
	 * Log the thrown exception and determined error page location with the given message, optionally parameterized
	 * with the given parameters.
	 * The default implementation logs through java.util.logging as SEVERE when the thrown exception is
	 * not an instance of any type specified in context parameter
	 * {@value org.omnifaces.exceptionhandler.FullAjaxExceptionHandler#PARAM_NAME_EXCEPTION_TYPES_TO_IGNORE_IN_LOGGING}.
	 * The log message will be prepended with the UUID and IP address.
	 * The UUID is available in EL by #{requestScope['org.omnifaces.exception_uuid']}.
	 * @param request The involved servlet request.
	 * @param exception The exception to log.
	 * @param location The error page location.
	 * @param message The log message.
	 * @param parameters The log message parameters, if any. They are formatted using {@link Formatter}.
	 * @since 3.2
	 */
	protected void logException
		(HttpServletRequest request, Throwable exception, String location, String message, Object... parameters)
	{
		if (!isOneInstanceOf(exception.getClass(), exceptionTypesToIgnoreInLogging)) {
			logger.log(SEVERE, format("[%s][%s] %s", request.getAttribute(EXCEPTION_UUID), getRemoteAddr(request), format(message, parameters)), exception);
		}
	}

}