LogManager

Class Overview

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.

Summary

[Expand] Inherited Methods

From class java.lang.Object Object clone() Creates and returns a copy of this Object. boolean equals(Object o) Compares this instance with the specified object and indicates if they are equal. void finalize() Called before the object's memory is reclaimed by the VM. final Class<?> getClass() Returns the unique instance of Class that represents this object's class. int hashCode() Returns an integer hash code for this object. final void notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up. final void notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up. String toString() Returns a string containing a concise, human-readable description of this object. final void wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object. final void wait(long millis, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires. final void wait(long millis) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.