org.springframework.web.util
Class Log4jWebConfigurer

java.lang.Object
  org.springframework.web.util.Log4jWebConfigurer

public abstract class Log4jWebConfigurer
extends java.lang.Object

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).

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 java.util.logging (which is global too).

Supports three init parameters at the servlet context level (that is, context-param entries in web.xml):

• "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).
• "log4jRefreshInterval":
  Interval between config file refresh checks, in milliseconds. If not specified, no refresh checks will happen, which avoids starting log4j's watchdog thread.
• "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.

Note: initLogging should be called before any other Spring activity (when using log4j), for proper initialization before any Spring logging attempts.

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.

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 not use config file refreshing in a production J2EE environment; the watchdog thread would not stop on application shutdown there.

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:

log4j.appender.myfile.File=${webapp.root}/WEB-INF/demo.log

Alternatively, specify a unique context-param "webAppRootKey" per web application. For example, with "webAppRootKey = "demo.root":

log4j.appender.myfile.File=${demo.root}/WEB-INF/demo.log

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.

Since:

12.08.2003

Author:

Juergen Hoeller

See Also:

Log4jConfigurer, Log4jConfigListener

Field Summary

static java.lang.String	CONFIG_LOCATION_PARAM Parameter specifying the location of the log4j config file
static java.lang.String	EXPOSE_WEB_APP_ROOT_PARAM Parameter specifying whether to expose the web app root system property
static java.lang.String	REFRESH_INTERVAL_PARAM Parameter specifying the refresh interval for checking the log4j config file

Constructor Summary

Log4jWebConfigurer()

Method Summary

private static boolean	exposeWebAppRoot(ServletContext servletContext) Return whether to expose the web app root system property, checking the corresponding ServletContext init parameter.
static void	initLogging(ServletContext servletContext) Initialize log4j, including setting the web app root system property.
static void	shutdownLogging(ServletContext servletContext) Shut down log4j, properly releasing all file locks and resetting the web app root system property.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

CONFIG_LOCATION_PARAM

public static final java.lang.String CONFIG_LOCATION_PARAM

Parameter specifying the location of the log4j config file

See Also:

Constant Field Values

REFRESH_INTERVAL_PARAM

public static final java.lang.String REFRESH_INTERVAL_PARAM

Parameter specifying the refresh interval for checking the log4j config file

See Also:

Constant Field Values

EXPOSE_WEB_APP_ROOT_PARAM

public static final java.lang.String EXPOSE_WEB_APP_ROOT_PARAM

Parameter specifying whether to expose the web app root system property

See Also:

Constant Field Values

Constructor Detail

Log4jWebConfigurer

public Log4jWebConfigurer()

Method Detail

initLogging

public static void initLogging(ServletContext servletContext)

Initialize log4j, including setting the web app root system property.

Parameters:

servletContext - the current ServletContext

See Also:

WebUtils.setWebAppRootSystemProperty(ServletContext)

shutdownLogging

public static void shutdownLogging(ServletContext servletContext)

Shut down log4j, properly releasing all file locks and resetting the web app root system property.

Parameters:

servletContext - the current ServletContext

See Also:

WebUtils.removeWebAppRootSystemProperty(ServletContext)

exposeWebAppRoot

private static boolean exposeWebAppRoot(ServletContext servletContext)

Return whether to expose the web app root system property, checking the corresponding ServletContext init parameter.

See Also:

EXPOSE_WEB_APP_ROOT_PARAM