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Spring Framework example source code file (Log4jWebConfigurer.java)

This example Spring Framework source code file (Log4jWebConfigurer.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Spring Framework tags/keywords

config_location_param, expose_web_app_root_param, filenotfoundexception, illegalargumentexception, illegalargumentexception, initializing, invalid, invalid, io, log4jwebconfigurer, refresh_interval_param, refresh_interval_param, servlet, shutting, string, string

The Spring Framework Log4jWebConfigurer.java source code

/*
 * Copyright 2002-2008 the original author or authors.
 *
 * 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
 *
 *      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.springframework.web.util;

import java.io.FileNotFoundException;

import javax.servlet.ServletContext;

import org.springframework.util.Log4jConfigurer;
import org.springframework.util.ResourceUtils;
import org.springframework.util.SystemPropertyUtils;

/**
 * Convenience class that performs custom log4j initialization for web environments,
 * allowing for log file paths within the web application, with the option to
 * perform automatic refresh checks (for runtime changes in logging configuration).
 *
 * <p>WARNING: Assumes an expanded WAR file, both for loading the configuration
 * file and for writing the log files. If you want to keep your WAR unexpanded or
 * don't need application-specific log files within the WAR directory, don't use
 * log4j setup within the application (thus, don't use Log4jConfigListener or
 * Log4jConfigServlet). Instead, use a global, VM-wide log4j setup (for example,
 * in JBoss) or JDK 1.4's <code>java.util.logging (which is global too).
 *
 * <p>Supports three init parameters at the servlet context level (that is,
 * context-param entries in web.xml):
 *
 * <ul>
 * <li>"log4jConfigLocation":
* Location of the log4j config file; either a "classpath:" location (e.g. * "classpath:myLog4j.properties"), an absolute file URL (e.g. "file:C:/log4j.properties), * or a plain path relative to the web application root directory (e.g. * "/WEB-INF/log4j.properties"). If not specified, default log4j initialization * will apply ("log4j.properties" or "log4j.xml" in the class path; see the * log4j documentation for details). * <li>"log4jRefreshInterval":
* Interval between config file refresh checks, in milliseconds. If not specified, * no refresh checks will happen, which avoids starting log4j's watchdog thread. * <li>"log4jExposeWebAppRoot":
* Whether the web app root system property should be exposed, allowing for log * file paths relative to the web application root directory. Default is "true"; * specify "false" to suppress expose of the web app root system property. See * below for details on how to use this system property in log file locations. * </ul> * * <p>Note: initLogging should be called before any other Spring activity * (when using log4j), for proper initialization before any Spring logging attempts. * * <p>Log4j's watchdog thread will asynchronously check whether the timestamp * of the config file has changed, using the given interval between checks. * A refresh interval of 1000 milliseconds (one second), which allows to * do on-demand log level changes with immediate effect, is not unfeasible. * <p>WARNING: Log4j's watchdog thread does not terminate until VM shutdown; * in particular, it does not terminate on LogManager shutdown. Therefore, it is * recommended to <i>not use config file refreshing in a production J2EE * environment; the watchdog thread would not stop on application shutdown there. * * <p>By default, this configurer automatically sets the web app root system property, * for "${key}" substitutions within log file locations in the log4j config file, * allowing for log file paths relative to the web application root directory. * The default system property key is "webapp.root", to be used in a log4j config * file like as follows: * * <p>log4j.appender.myfile.File=${webapp.root}/WEB-INF/demo.log * * <p>Alternatively, specify a unique context-param "webAppRootKey" per web application. * For example, with "webAppRootKey = "demo.root": * * <p>log4j.appender.myfile.File=${demo.root}/WEB-INF/demo.log * * <p>WARNING: Some containers (like Tomcat) do not keep system properties * separate per web app. You have to use unique "webAppRootKey" context-params per web * app then, to avoid clashes. Other containers like Resin do isolate each web app's * system properties: Here you can use the default key (i.e. no "webAppRootKey" * context-param at all) without worrying. * * @author Juergen Hoeller * @since 12.08.2003 * @see org.springframework.util.Log4jConfigurer * @see Log4jConfigListener * @see Log4jConfigServlet */ public abstract class Log4jWebConfigurer { /** Parameter specifying the location of the log4j config file */ public static final String CONFIG_LOCATION_PARAM = "log4jConfigLocation"; /** Parameter specifying the refresh interval for checking the log4j config file */ public static final String REFRESH_INTERVAL_PARAM = "log4jRefreshInterval"; /** Parameter specifying whether to expose the web app root system property */ public static final String EXPOSE_WEB_APP_ROOT_PARAM = "log4jExposeWebAppRoot"; /** * Initialize log4j, including setting the web app root system property. * @param servletContext the current ServletContext * @see WebUtils#setWebAppRootSystemProperty */ public static void initLogging(ServletContext servletContext) { // Expose the web app root system property. if (exposeWebAppRoot(servletContext)) { WebUtils.setWebAppRootSystemProperty(servletContext); } // Only perform custom log4j initialization in case of a config file. String location = servletContext.getInitParameter(CONFIG_LOCATION_PARAM); if (location != null) { // Perform actual log4j initialization; else rely on log4j's default initialization. try { // Return a URL (e.g. "classpath:" or "file:") as-is; // consider a plain file path as relative to the web application root directory. if (!ResourceUtils.isUrl(location)) { // Resolve system property placeholders before resolving real path. location = SystemPropertyUtils.resolvePlaceholders(location); location = WebUtils.getRealPath(servletContext, location); } // Write log message to server log. servletContext.log("Initializing log4j from [" + location + "]"); // Check whether refresh interval was specified. String intervalString = servletContext.getInitParameter(REFRESH_INTERVAL_PARAM); if (intervalString != null) { // Initialize with refresh interval, i.e. with log4j's watchdog thread, // checking the file in the background. try { long refreshInterval = Long.parseLong(intervalString); Log4jConfigurer.initLogging(location, refreshInterval); } catch (NumberFormatException ex) { throw new IllegalArgumentException("Invalid 'log4jRefreshInterval' parameter: " + ex.getMessage()); } } else { // Initialize without refresh check, i.e. without log4j's watchdog thread. Log4jConfigurer.initLogging(location); } } catch (FileNotFoundException ex) { throw new IllegalArgumentException("Invalid 'log4jConfigLocation' parameter: " + ex.getMessage()); } } } /** * Shut down log4j, properly releasing all file locks * and resetting the web app root system property. * @param servletContext the current ServletContext * @see WebUtils#removeWebAppRootSystemProperty */ public static void shutdownLogging(ServletContext servletContext) { servletContext.log("Shutting down log4j"); try { Log4jConfigurer.shutdownLogging(); } finally { // Remove the web app root system property. if (exposeWebAppRoot(servletContext)) { WebUtils.removeWebAppRootSystemProperty(servletContext); } } } /** * Return whether to expose the web app root system property, * checking the corresponding ServletContext init parameter. * @see #EXPOSE_WEB_APP_ROOT_PARAM */ private static boolean exposeWebAppRoot(ServletContext servletContext) { String exposeWebAppRootParam = servletContext.getInitParameter(EXPOSE_WEB_APP_ROOT_PARAM); return (exposeWebAppRootParam == null || Boolean.valueOf(exposeWebAppRootParam).booleanValue()); } }

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