Package java.util.logging

Class LogManager

java.lang.Object
java.util.logging.LogManager
public class LogManager
extends Object
LogManager is used to maintain configuration properties of the logging framework, and to manage a hierarchical namespace of all named Logger objects.

There is only one global LogManager instance in the application, which can be get by calling static method getLogManager(). This instance is created and initialized during class initialization and cannot be changed.

The LogManager class can be specified by java.util.logging.manager system property, if the property is unavailable or invalid, the default class LogManager will be used.

On initialization, LogManager reads its configuration from a properties file, which by default is the "lib/logging.properties" in the JRE directory.

However, two optional system properties can be used to customize the initial configuration process of LogManager.

  • "java.util.logging.config.class"
  • "java.util.logging.config.file"

These two properties can be set in three ways, by the Preferences API, by the "java" command line property definitions, or by system property definitions passed to JNI_CreateJavaVM.

The "java.util.logging.config.class" should specifies a class name. If it is set, this given class will be loaded and instantiated during LogManager initialization, so that this object's default constructor can read the initial configuration and define properties for LogManager.

If "java.util.logging.config.class" property is not set, or it is invalid, or some exception is thrown during the instantiation, then the "java.util.logging.config.file" system property can be used to specify a properties file. The LogManager will read initial configuration from this file.

If neither of these properties is defined, or some exception is thrown during these two properties using, the LogManager will read its initial configuration from default properties file, as described above.

The global logging properties may include:

  • "handlers". This property's values should be a list of class names for handler classes separated by whitespace, these classes must be subclasses of Handler and each must have a default constructor, these classes will be loaded, instantiated and registered as handlers on the root Logger (the Logger named ""). These Handlers maybe initialized lazily.
  • "config". The property defines a list of class names separated by whitespace. Each class must have a default constructor, in which it can update the logging configuration, such as levels, handlers, or filters for some logger, etc. These classes will be loaded and instantiated during LogManager configuration

This class, together with any handler and configuration classes associated with it, must be loaded from the system classpath when LogManager configuration occurs.

Besides global properties, the properties for loggers and Handlers can be specified in the property files. The names of these properties will start with the complete dot separated names for the handlers or loggers.

In the LogManager's hierarchical namespace, Loggers are organized based on their dot separated names. For example, "x.y.z" is child of "x.y".

Levels for Loggers can be defined by properties whose name end with ".level". Thus "alogger.level" defines a level for the logger named as "alogger" and for all its children in the naming hierarchy. Log levels properties are read and applied in the same order as they are specified in the property file. The root logger's level can be defined by the property named as ".level".

This class is thread safe. It is an error to synchronize on a LogManager while synchronized on a Logger.

  • Field Details

  • Constructor Details

    • LogManager

      protected LogManager()
      Default constructor. This is not public because there should be only one LogManager instance, which can be get by LogManager.getLogManager(). This is protected so that application can subclass the object.

  • Method Details

    • getLoggingMXBean

      public static LoggingMXBean getLoggingMXBean()
      Get the LoggingMXBean instance. this implementation always throws an UnsupportedOperationException.
      Returns:
      the LoggingMXBean instance

    • checkAccess

      public void checkAccess()
      Does nothing.

    • addLogger

      public boolean addLogger​(Logger logger)
      Add a given logger into the hierarchical namespace. The Logger.addLogger() factory methods call this method to add newly created Logger. This returns false if a logger with the given name has existed in the namespace

      Note that the LogManager may only retain weak references to registered loggers. In order to prevent Logger objects from being unexpectedly garbage collected it is necessary for applications to maintain references to them.

      Parameters:
      logger - the logger to be added.
      Returns:
      true if the given logger is added into the namespace successfully, false if the given logger exists in the namespace.

    • getLogger

      public Logger getLogger​(String name)
      Get the logger with the given name.
      Parameters:
      name - name of logger
      Returns:
      logger with given name, or null if nothing is found.

    • getLoggerNames

      public Enumeration<String> getLoggerNames()
      Get a Enumeration of all registered logger names.
      Returns:
      enumeration of registered logger names

    • getLogManager

      public static LogManager getLogManager()
      Get the global LogManager instance.
      Returns:
      the global LogManager instance

    • getProperty

      public String getProperty​(String name)
      Get the value of property with given name.
      Parameters:
      name - the name of property
      Returns:
      the value of property

    • readConfiguration

      public void readConfiguration() throws IOException
      Re-initialize the properties and configuration. The initialization process is same as the LogManager instantiation.

      Notice : No PropertyChangeEvent are fired.

      Throws:
      IOException - if any IO related problems happened.

    • readConfiguration

      public void readConfiguration​(InputStream ins) throws IOException
      Re-initialize the properties and configuration from the given InputStream

      Notice : No PropertyChangeEvent are fired.

      Parameters:
      ins - the input stream
      Throws:
      IOException - if any IO related problems happened.

    • reset

      public void reset()
      Reset configuration.

      All handlers are closed and removed from any named loggers. All loggers' level is set to null, except the root logger's level is set to Level.INFO.

    • addPropertyChangeListener

      public void addPropertyChangeListener​(PropertyChangeListener l)
      Add a PropertyChangeListener, which will be invoked when the properties are reread.
      Parameters:
      l - the PropertyChangeListener to be added.

    • removePropertyChangeListener

      public void removePropertyChangeListener​(PropertyChangeListener l)
      Remove a PropertyChangeListener, do nothing if the given listener is not found.
      Parameters:
      l - the PropertyChangeListener to be removed.