There is a single global LogManager object that is used to maintain a set of shared state about Loggers and log services.
This LogManager object:
- Manages a hierarchical namespace of Logger objects. All named Loggers are stored in this namespace.
- Manages a set of logging control properties. These are simple key-value pairs that can be used by Handlers and other logging objects to configure themselves.
The global LogManager object can be retrieved using LogManager.getLogManager(). The LogManager object is created during class initialization and cannot subsequently be changed.
At startup the LogManager class is located using the java.util.logging.manager system property.
By default, the LogManager reads its initial configuration from a properties file "lib/logging.properties" in the JRE directory. If you edit that property file you can change the default logging configuration for all uses of that JRE.
In addition, the LogManager uses two optional system properties that allow more control over reading the initial configuration:
If the "java.util.logging.config.class" property is set, then the property value is treated as a class name. The given class will be loaded, an object will be instantiated, and that object's constructor is responsible for reading in the initial configuration. (That object may use other system properties to control its configuration.) The alternate configuration class can use readConfiguration(InputStream) to define properties in the LogManager.
If "java.util.logging.config.class" property is not set, then the "java.util.logging.config.file" system property can be used to specify a properties file (in java.util.Properties format). The initial logging configuration will be read from this file.
If neither of these properties is defined then, as described above, the LogManager will read its initial configuration from a properties file "lib/logging.properties" in the JRE directory.
The properties for loggers and Handlers will have names starting with the dot-separated name for the handler or logger.
The global logging properties may include:
- A property "handlers". This defines a whitespace or comma separated list of class names for handler classes to load and register as handlers on the root Logger (the Logger named ""). Each class name must be for a Handler class which has a default constructor. Note that these Handlers may be created lazily, when they are first used.
- A property "<logger>.handlers". This defines a whitespace or comma separated list of class names for handlers classes to load and register as handlers to the specified logger. Each class name must be for a Handler class which has a default constructor. Note that these Handlers may be created lazily, when they are first used.
- A property "<logger>.useParentHandlers". This defines a boolean value. By default every logger calls its parent in addition to handling the logging message itself, this often result in messages being handled by the root logger as well. When setting this property to false a Handler needs to be configured for this logger otherwise no logging messages are delivered.
- A property "config". This property is intended to allow arbitrary configuration code to be run. The property defines a whitespace or comma separated list of class names. A new instance will be created for each named class. The default constructor of each class may execute arbitrary code to update the logging configuration, such as setting logger levels, adding handlers, adding filters, etc.
Note that all classes loaded during LogManager configuration are first searched on the system class path before any user class path. That includes the LogManager class, any config classes, and any handler classes.
Loggers are organized into a naming hierarchy based on their dot separated names. Thus "a.b.c" is a child of "a.b", but "a.b1" and a.b2" are peers.
All properties whose names end with ".level" are assumed to define log levels for Loggers. Thus "foo.level" defines a log level for the logger called "foo" and (recursively) for any of its children in the naming hierarchy. Log Levels are applied in the order they are defined in the properties file. Thus level settings for child nodes in the tree should come after settings for their parents. The property name ".level" can be used to set the level for the root of the tree.
All methods on the LogManager object are multi-thread safe.