/*
* 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><b>WARNING: Assumes an expanded WAR file</b>, 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</code> (which is global too).
*
* <p>Supports three init parameters at the servlet context level (that is,
* context-param entries in web.xml):
*
* <ul>
* <li><i>"log4jConfigLocation":</i><br>
* 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><i>"log4jRefreshInterval":</i><br>
* Interval between config file refresh checks, in milliseconds. If not specified,
* no refresh checks will happen, which avoids starting log4j's watchdog thread.
* <li><i>"log4jExposeWebAppRoot":</i><br>
* 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: <code>initLogging</code> 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><b>WARNING:</b> 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</i> 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 "${key}" substitutions within log file locations in the log4j config file,
* allowing for log file paths relative to the web application root directory.
* The default system property key is "webapp.root", to be used in a log4j config
* file like as follows:
*
* <p><code>log4j.appender.myfile.File=${webapp.root}/WEB-INF/demo.log</code>
*
* <p>Alternatively, specify a unique context-param "webAppRootKey" per web application.
* For example, with "webAppRootKey = "demo.root":
*
* <p><code>log4j.appender.myfile.File=${demo.root}/WEB-INF/demo.log</code>
*
* <p><b>WARNING:</b> Some containers (like Tomcat) do <i>not</i> 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());
}
}