org.springframework.util

## Class Log4jConfigurer

- java.lang.Object
- - org.springframework.util.Log4jConfigurer

-     public abstract class Log4jConfigurer
      extends Object

  Convenience class that features simple methods for custom log4j configuration.

  Only needed for non-default log4j initialization, for example with a custom config location or a refresh interval. By default, log4j will simply read its configuration from a "log4j.properties" or "log4j.xml" file in the root of the classpath.

  For web environments, the analogous Log4jWebConfigurer class can be found in the web package, reading in its configuration from context-params in `web.xml`. In a J2EE web application, log4j is usually set up via Log4jConfigListener or Log4jConfigServlet, delegating to Log4jWebConfigurer underneath.

  Since:
    13.03.2003
  Author:
    Juergen Hoeller
  See Also:
    `Log4jWebConfigurer`, `Log4jConfigListener`

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static String` | `CLASSPATH_URL_PREFIX` Pseudo URL prefix for loading from the class path: "classpath:"
    `static String` | `XML_FILE_EXTENSION` Extension that indicates a log4j XML config file: ".xml"

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `Log4jConfigurer()`

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `static void` | `initLogging(String location)` Initialize log4j from the given file location, with no config file refreshing.
    `static void` | `initLogging(String location, long refreshInterval)` Initialize log4j from the given location, with the given refresh interval for the config file.
    `static void` | `setWorkingDirSystemProperty(String key)` Set the specified system property to the current working directory.
    `static void` | `shutdownLogging()` Shut down log4j, properly releasing all file locks.

    - ### Methods inherited from class java.lang.Object

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

- - ### Field Detail

    - #### CLASSPATH_URL_PREFIX

          public static final String CLASSPATH_URL_PREFIX

      Pseudo URL prefix for loading from the class path: "classpath:"
      See Also:
        Constant Field Values

    - #### XML_FILE_EXTENSION

          public static final String XML_FILE_EXTENSION

      Extension that indicates a log4j XML config file: ".xml"
      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### Log4jConfigurer

          public Log4jConfigurer()

  - ### Method Detail

    - #### initLogging

          public static void initLogging(String location)
                                  throws FileNotFoundException

      Initialize log4j from the given file location, with no config file refreshing. Assumes an XML file in case of a ".xml" file extension, and a properties file otherwise.
      Parameters:
        `location` - the location of the config file: either a "classpath:" location (e.g. "classpath:myLog4j.properties"), an absolute file URL (e.g. "file:C:/log4j.properties), or a plain absolute path in the file system (e.g. "C:/log4j.properties")
      Throws:
        `FileNotFoundException` - if the location specifies an invalid file path

    - #### initLogging

          public static void initLogging(String location,
                         long refreshInterval)
                                  throws FileNotFoundException

      Initialize log4j from the given location, with the given refresh interval for the config file. Assumes an XML file in case of a ".xml" file extension, and a properties file otherwise.

      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.

      Parameters:
        `location` - the location of the config file: either a "classpath:" location (e.g. "classpath:myLog4j.properties"), an absolute file URL (e.g. "file:C:/log4j.properties), or a plain absolute path in the file system (e.g. "C:/log4j.properties")
        `refreshInterval` - interval between config file refresh checks, in milliseconds
      Throws:
        `FileNotFoundException` - if the location specifies an invalid file path

    - #### shutdownLogging

          public static void shutdownLogging()

      Shut down log4j, properly releasing all file locks.

      This isn't strictly necessary, but recommended for shutting down log4j in a scenario where the host VM stays alive (for example, when shutting down an application in a J2EE environment).

    - #### setWorkingDirSystemProperty

          public static void setWorkingDirSystemProperty(String key)

      Set the specified system property to the current working directory.

      This can be used e.g. for test environments, for applications that leverage Log4jWebConfigurer's "webAppRootKey" support in a web environment.

      Parameters:
        `key` - system property key to use, as expected in Log4j configuration (for example: "demo.root", used as "${demo.root}/WEB-INF/demo.log")
      See Also:
        `Log4jWebConfigurer`