Added in API level 1

Logger

open class Logger
kotlin.Any
   ↳ java.util.logging.Logger

A Logger object is used to log messages for a specific system or application component. Loggers are normally named, using a hierarchical dot-separated namespace. Logger names can be arbitrary strings, but they should normally be based on the package name or class name of the logged component, such as java.net or javax.swing. In addition it is possible to create "anonymous" Loggers that are not stored in the Logger namespace.

Logger objects may be obtained by calls on one of the getLogger factory methods. These will either create a new Logger or return a suitable existing Logger. It is important to note that the Logger returned by one of the getLogger factory methods may be garbage collected at any time if a strong reference to the Logger is not kept.

Logging messages will be forwarded to registered Handler objects, which can forward the messages to a variety of destinations, including consoles, files, OS logs, etc.

Each Logger keeps track of a "parent" Logger, which is its nearest existing ancestor in the Logger namespace.

Each Logger has a "Level" associated with it. This reflects a minimum Level that this logger cares about. If a Logger's level is set to null, then its effective level is inherited from its parent, which may in turn obtain it recursively from its parent, and so on up the tree.

The log level can be configured based on the properties from the logging configuration file, as described in the description of the LogManager class. However it may also be dynamically changed by calls on the Logger.setLevel method. If a logger's level is changed the change may also affect child loggers, since any child logger that has null as its level will inherit its effective level from its parent.

On each logging call the Logger initially performs a cheap check of the request level (e.g., SEVERE or FINE) against the effective log level of the logger. If the request level is lower than the log level, the logging call returns immediately.

After passing this initial (cheap) test, the Logger will allocate a LogRecord to describe the logging message. It will then call a Filter (if present) to do a more detailed check on whether the record should be published. If that passes it will then publish the LogRecord to its output Handlers. By default, loggers also publish to their parent's Handlers, recursively up the tree.

Each Logger may have a ResourceBundle associated with it. The ResourceBundle may be specified by name, using the getLogger(java.lang.String,java.lang.String) factory method, or by value - using the setResourceBundle method. This bundle will be used for localizing logging messages. If a Logger does not have its own ResourceBundle or resource bundle name, then it will inherit the ResourceBundle or resource bundle name from its parent, recursively up the tree.

Most of the logger output methods take a "msg" argument. This msg argument may be either a raw value or a localization key. During formatting, if the logger has (or inherits) a localization ResourceBundle and if the ResourceBundle has a mapping for the msg string, then the msg string is replaced by the localized value. Otherwise the original msg string is used. Typically, formatters use java.text.MessageFormat style formatting to format parameters, so for example a format string "{0} {1}" would format two parameters as strings.

A set of methods alternatively take a "msgSupplier" instead of a "msg" argument. These methods take a Supplier<String> function which is invoked to construct the desired log message only when the message actually is to be logged based on the effective log level thus eliminating unnecessary message construction. For example, if the developer wants to log system health status for diagnosis, with the String-accepting version, the code would look like: 

<code>
 
  class DiagnosisMessages {
    static String systemHealthStatus() {
      // collect system health information
      ...
    }
  }
  ...
  logger.log(Level.FINER, DiagnosisMessages.systemHealthStatus());
 </code>
 With the above code, the health status is collected unnecessarily even when the log level FINER is disabled. With the Supplier-accepting version as below, the status will only be collected when the log level FINER is enabled. 
<code>
 
  logger.log(Level.FINER, DiagnosisMessages::systemHealthStatus);
 </code>

When looking for a ResourceBundle, the logger will first look at whether a bundle was specified using setResourceBundle, and then only whether a resource bundle name was specified through the getLogger factory method. If no ResourceBundle or no resource bundle name is found, then it will use the nearest ResourceBundle or resource bundle name inherited from its parent tree.
When a ResourceBundle was inherited or specified through the setResourceBundle method, then that ResourceBundle will be used. Otherwise if the logger only has or inherited a resource bundle name, then that resource bundle name will be mapped to a ResourceBundle object, using the default Locale at the time of logging.
When mapping resource bundle names to ResourceBundle objects, the logger will first try to use the Thread's context class to map the given resource bundle name to a ResourceBundle. If the thread context class loader is null, it will try the system class loader instead. If the ResourceBundle is still not found, it will use the class loader of the first caller of the getLogger factory method.

Formatting (including localization) is the responsibility of the output Handler, which will typically call a Formatter.

Note that formatting need not occur synchronously. It may be delayed until a LogRecord is actually written to an external sink.

The logging methods are grouped in five main categories:

  • There are a set of "log" methods that take a log level, a message string, and optionally some parameters to the message string.
  • There are a set of "logp" methods (for "log precise") that are like the "log" methods, but also take an explicit source class name and method name.
  • There are a set of "logrb" method (for "log with resource bundle") that are like the "logp" method, but also take an explicit resource bundle object for use in localizing the log message.
  • There are convenience methods for tracing method entries (the "entering" methods), method returns (the "exiting" methods) and throwing exceptions (the "throwing" methods).
  • Finally, there are a set of convenience methods for use in the very simplest cases, when a developer simply wants to log a simple string at a given log level. These methods are named after the standard Level names ("severe", "warning", "info", etc.) and take a single argument, a message string.

For the methods that do not take an explicit source name and method name, the Logging framework will make a "best effort" to determine which class and method called into the logging method. However, it is important to realize that this automatically inferred information may only be approximate (or may even be quite wrong!). Virtual machines are allowed to do extensive optimizations when JITing and may entirely remove stack frames, making it impossible to reliably locate the calling class and method.

All methods on Logger are multi-thread safe.

Subclassing Information: Note that a LogManager class may provide its own implementation of named Loggers for any point in the namespace. Therefore, any subclasses of Logger (unless they are implemented in conjunction with a new LogManager class) should take care to obtain a Logger instance from the LogManager class and should delegate operations such as "isLoggable" and "log(LogRecord)" to that instance. Note that in order to intercept all logging output, subclasses need only override the log(LogRecord) method. All the other logging methods are implemented as calls on this log(LogRecord) method.

Summary

Constants
static String

GLOBAL_LOGGER_NAME is a name for the global logger.
Protected constructors
Logger(name: String?, resourceBundleName: String?)

Protected method to construct a logger for a named subsystem.
Public methods
open Unit
addHandler(handler: Handler)

Add a log Handler to receive logging messages.
open Unit
config(msg: String?)

Log a CONFIG message.
open Unit
config(msgSupplier: Supplier<String!>)

Log a CONFIG message, which is only to be constructed if the logging level is such that the message will actually be logged.
open Unit
entering(sourceClass: String?, sourceMethod: String?)

Log a method entry.
open Unit
entering(sourceClass: String?, sourceMethod: String?, param1: Any?)

Log a method entry, with one parameter.
open Unit
entering(sourceClass: String?, sourceMethod: String?, params: Array<Any!>?)

Log a method entry, with an array of parameters.
open Unit
exiting(sourceClass: String?, sourceMethod: String?)

Log a method return.
open Unit
exiting(sourceClass: String?, sourceMethod: String?, result: Any?)

Log a method return, with result object.
open Unit
fine(msg: String?)

Log a FINE message.
open Unit
fine(msgSupplier: Supplier<String!>)

Log a FINE message, which is only to be constructed if the logging level is such that the message will actually be logged.
open Unit
finer(msg: String?)

Log a FINER message.
open Unit
finer(msgSupplier: Supplier<String!>)

Log a FINER message, which is only to be constructed if the logging level is such that the message will actually be logged.
open Unit
finest(msg: String?)

Log a FINEST message.
open Unit
finest(msgSupplier: Supplier<String!>)

Log a FINEST message, which is only to be constructed if the logging level is such that the message will actually be logged.
open static Logger

Create an anonymous Logger.
open static Logger
getAnonymousLogger(resourceBundleName: String?)

Create an anonymous Logger.
open Filter?

Get the current filter for this Logger.
static Logger

Return global logger object with the name Logger.
open Array<Handler!>

Get the Handlers associated with this logger.
open Level?

Get the log Level that has been specified for this Logger.
open static Logger

Find or create a logger for a named subsystem.
open static Logger
getLogger(name: String, resourceBundleName: String?)

Find or create a logger for a named subsystem.
open String?

Get the name for this logger.
open Logger?

Return the parent for this Logger.
open ResourceBundle?

Retrieve the localization resource bundle for this logger.
open String?

Retrieve the localization resource bundle name for this logger.
open Boolean

Discover whether or not this logger is sending its output to its parent logger.
open Unit
info(msg: String?)

Log an INFO message.
open Unit
info(msgSupplier: Supplier<String!>)

Log a INFO message, which is only to be constructed if the logging level is such that the message will actually be logged.
open Boolean
isLoggable(level: Level)

Check if a message of the given level would actually be logged by this logger.
open Unit
log(level: Level, msg: String?)

Log a message, with no arguments.
open Unit
log(level: Level, msg: String?, param1: Any?)

Log a message, with one object parameter.
open Unit
log(level: Level, msg: String?, params: Array<Any!>?)

Log a message, with an array of object arguments.
open Unit
log(level: Level, msg: String?, thrown: Throwable?)

Log a message, with associated Throwable information.
open Unit
log(level: Level, thrown: Throwable?, msgSupplier: Supplier<String!>)

Log a lazily constructed message, with associated Throwable information.
open Unit
log(level: Level, msgSupplier: Supplier<String!>)

Log a message, which is only to be constructed if the logging level is such that the message will actually be logged.
open Unit
log(record: LogRecord)

Log a LogRecord.
open Unit
logp(level: Level, sourceClass: String?, sourceMethod: String?, msg: String?)

Log a message, specifying source class and method, with no arguments.
open Unit
logp(level: Level, sourceClass: String?, sourceMethod: String?, msg: String?, param1: Any?)

Log a message, specifying source class and method, with a single object parameter to the log message.
open Unit
logp(level: Level, sourceClass: String?, sourceMethod: String?, msg: String?, params: Array<Any!>?)

Log a message, specifying source class and method, with an array of object arguments.
open Unit
logp(level: Level, sourceClass: String?, sourceMethod: String?, msg: String?, thrown: Throwable?)

Log a message, specifying source class and method, with associated Throwable information.
open Unit
logp(level: Level, sourceClass: String?, sourceMethod: String?, thrown: Throwable?, msgSupplier: Supplier<String!>)

Log a lazily constructed message, specifying source class and method, with associated Throwable information.
open Unit
logp(level: Level, sourceClass: String?, sourceMethod: String?, msgSupplier: Supplier<String!>)

Log a lazily constructed message, specifying source class and method, with no arguments.
open Unit
logrb(level: Level, sourceClass: String?, sourceMethod: String?, bundleName: String?, msg: String?)

Log a message, specifying source class, method, and resource bundle name with no arguments.
open Unit
logrb(level: Level, sourceClass: String?, sourceMethod: String?, bundleName: String?, msg: String?, param1: Any?)

Log a message, specifying source class, method, and resource bundle name, with a single object parameter to the log message.
open Unit
logrb(level: Level, sourceClass: String?, sourceMethod: String?, bundleName: String?, msg: String?, params: Array<Any!>?)

Log a message, specifying source class, method, and resource bundle name, with an array of object arguments.
open Unit
logrb(level: Level, sourceClass: String?, sourceMethod: String?, bundleName: String?, msg: String?, thrown: Throwable?)

Log a message, specifying source class, method, and resource bundle name, with associated Throwable information.
open Unit
logrb(level: Level, sourceClass: String?, sourceMethod: String?, bundle: ResourceBundle?, msg: String?, vararg params: Any!)

Log a message, specifying source class, method, and resource bundle, with an optional list of message parameters.
open Unit
logrb(level: Level, sourceClass: String?, sourceMethod: String?, bundle: ResourceBundle?, msg: String?, thrown: Throwable?)

Log a message, specifying source class, method, and resource bundle, with associated Throwable information.
open Unit

Remove a log Handler.
open Unit
setFilter(newFilter: Filter?)

Set a filter to control output on this Logger.
open Unit
setLevel(newLevel: Level?)

Set the log level specifying which message levels will be logged by this logger.
open Unit
setParent(parent: Logger)

Set the parent for this Logger.
open Unit

Sets a resource bundle on this logger.
open Unit
setUseParentHandlers(useParentHandlers: Boolean)

Specify whether or not this logger should send its output to its parent Logger.
open Unit
severe(msg: String?)

Log a SEVERE message.
open Unit
severe(msgSupplier: Supplier<String!>)

Log a SEVERE message, which is only to be constructed if the logging level is such that the message will actually be logged.
open Unit
throwing(sourceClass: String?, sourceMethod: String?, thrown: Throwable?)

Log throwing an exception.
open Unit
warning(msg: String?)

Log a WARNING message.
open Unit
warning(msgSupplier: Supplier<String!>)

Log a WARNING message, which is only to be constructed if the logging level is such that the message will actually be logged.
Properties
static Logger

The "global" Logger object is provided as a convenience to developers who are making casual use of the Logging package.

Constants

GLOBAL_LOGGER_NAME

Added in API level 9
static val GLOBAL_LOGGER_NAME: String

GLOBAL_LOGGER_NAME is a name for the global logger.

Value: "global"

Protected constructors

Logger

Added in API level 1
protected Logger(
    name: String?, 
    resourceBundleName: String?)

Protected method to construct a logger for a named subsystem.

The logger will be initially configured with a null Level and with useParentHandlers set to true.

Parameters
name String?: A name for the logger. This should be a dot-separated name and should normally be based on the package name or class name of the subsystem, such as java.net or javax.swing. It may be null for anonymous Loggers.
resourceBundleName String?: name of ResourceBundle to be used for localizing messages for this logger. May be null if none of the messages require localization.
Exceptions
java.util.MissingResourceException if the resourceBundleName is non-null and no corresponding resource can be found.

Public methods

addHandler

Added in API level 1
open fun addHandler(handler: Handler): Unit

Add a log Handler to receive logging messages.

By default, Loggers also send their output to their parent logger. Typically the root Logger is configured with a set of Handlers that essentially act as default handlers for all loggers.

Parameters
handler Handler: a logging Handler
Exceptions
java.lang.SecurityException if a security manager exists, this logger is not anonymous, and the caller does not have LoggingPermission("control").

config

Added in API level 1
open fun config(msg: String?): Unit

Log a CONFIG message.

If the logger is currently enabled for the CONFIG message level then the given message is forwarded to all the registered output Handler objects.

Parameters
msg String?: The string message (or a key in the message catalog)

config

Added in API level 26
open fun config(msgSupplier: Supplier<String!>): Unit

Log a CONFIG message, which is only to be constructed if the logging level is such that the message will actually be logged.

If the logger is currently enabled for the CONFIG message level then the message is constructed by invoking the provided supplier function and forwarded to all the registered output Handler objects.

Parameters
msgSupplier Supplier<String!>: A function, which when called, produces the desired log message

entering

Added in API level 1
open fun entering(
    sourceClass: String?, 
    sourceMethod: String?
): Unit

Log a method entry.

This is a convenience method that can be used to log entry to a method. A LogRecord with message "ENTRY", log level FINER, and the given sourceMethod and sourceClass is logged.

Parameters
sourceClass String?: name of class that issued the logging request
sourceMethod String?: name of method that is being entered

entering

Added in API level 1
open fun entering(
    sourceClass: String?, 
    sourceMethod: String?, 
    param1: Any?
): Unit

Log a method entry, with one parameter.

This is a convenience method that can be used to log entry to a method. A LogRecord with message "ENTRY {0}", log level FINER, and the given sourceMethod, sourceClass, and parameter is logged.

Parameters
sourceClass String?: name of class that issued the logging request
sourceMethod String?: name of method that is being entered
param1 Any?: parameter to the method being entered

entering

Added in API level 1
open fun entering(
    sourceClass: String?, 
    sourceMethod: String?, 
    params: Array<Any!>?
): Unit

Log a method entry, with an array of parameters.

This is a convenience method that can be used to log entry to a method. A LogRecord with message "ENTRY" (followed by a format {N} indicator for each entry in the parameter array), log level FINER, and the given sourceMethod, sourceClass, and parameters is logged.

Parameters
sourceClass String?: name of class that issued the logging request
sourceMethod String?: name of method that is being entered
params Array<Any!>?: array of parameters to the method being entered

exiting

Added in API level 1
open fun exiting(
    sourceClass: String?, 
    sourceMethod: String?
): Unit

Log a method return.

This is a convenience method that can be used to log returning from a method. A LogRecord with message "RETURN", log level FINER, and the given sourceMethod and sourceClass is logged.

Parameters
sourceClass String?: name of class that issued the logging request
sourceMethod String?: name of the method

exiting

Added in API level 1
open fun exiting(
    sourceClass: String?, 
    sourceMethod: String?, 
    result: Any?
): Unit

Log a method return, with result object.

This is a convenience method that can be used to log returning from a method. A LogRecord with message "RETURN {0}", log level FINER, and the gives sourceMethod, sourceClass, and result object is logged.

Parameters
sourceClass String?: name of class that issued the logging request
sourceMethod String?: name of the method
result Any?: Object that is being returned

fine

Added in API level 1
open fun fine(msg: String?): Unit

Log a FINE message.

If the logger is currently enabled for the FINE message level then the given message is forwarded to all the registered output Handler objects.

Parameters
msg String?: The string message (or a key in the message catalog)

fine

Added in API level 26
open fun fine(msgSupplier: Supplier<String!>): Unit

Log a FINE message, which is only to be constructed if the logging level is such that the message will actually be logged.

If the logger is currently enabled for the FINE message level then the message is constructed by invoking the provided supplier function and forwarded to all the registered output Handler objects.

Parameters
msgSupplier Supplier<String!>: A function, which when called, produces the desired log message

finer

Added in API level 1
open fun finer(msg: String?): Unit

Log a FINER message.

If the logger is currently enabled for the FINER message level then the given message is forwarded to all the registered output Handler objects.

Parameters
msg String?: The string message (or a key in the message catalog)

finer

Added in API level 26
open fun finer(msgSupplier: Supplier<String!>): Unit

Log a FINER message, which is only to be constructed if the logging level is such that the message will actually be logged.

If the logger is currently enabled for the FINER message level then the message is constructed by invoking the provided supplier function and forwarded to all the registered output Handler objects.

Parameters
msgSupplier Supplier<String!>: A function, which when called, produces the desired log message

finest

Added in API level 1
open fun finest(msg: String?): Unit

Log a FINEST message.

If the logger is currently enabled for the FINEST message level then the given message is forwarded to all the registered output Handler objects.

Parameters
msg String?: The string message (or a key in the message catalog)

finest

Added in API level 26
open fun finest(msgSupplier: Supplier<String!>): Unit

Log a FINEST message, which is only to be constructed if the logging level is such that the message will actually be logged.

If the logger is currently enabled for the FINEST message level then the message is constructed by invoking the provided supplier function and forwarded to all the registered output Handler objects.

Parameters
msgSupplier Supplier<String!>: A function, which when called, produces the desired log message

getAnonymousLogger

Added in API level 1
open static fun getAnonymousLogger(): Logger

Create an anonymous Logger. The newly created Logger is not registered in the LogManager namespace. There will be no access checks on updates to the logger.

This factory method is primarily intended for use from applets. Because the resulting Logger is anonymous it can be kept private by the creating class. This removes the need for normal security checks, which in turn allows untrusted applet code to update the control state of the Logger. For example an applet can do a setLevel or an addHandler on an anonymous Logger.

Even although the new logger is anonymous, it is configured to have the root logger ("") as its parent. This means that by default it inherits its effective level and handlers from the root logger. Changing its parent via the setParent method will still require the security permission specified by that method.

Return
Logger a newly created private Logger

getAnonymousLogger

Added in API level 1
open static fun getAnonymousLogger(resourceBundleName: String?): Logger

Create an anonymous Logger. The newly created Logger is not registered in the LogManager namespace. There will be no access checks on updates to the logger.

This factory method is primarily intended for use from applets. Because the resulting Logger is anonymous it can be kept private by the creating class. This removes the need for normal security checks, which in turn allows untrusted applet code to update the control state of the Logger. For example an applet can do a setLevel or an addHandler on an anonymous Logger.

Even although the new logger is anonymous, it is configured to have the root logger ("") as its parent. This means that by default it inherits its effective level and handlers from the root logger. Changing its parent via the setParent method will still require the security permission specified by that method.

Parameters
resourceBundleName String?: name of ResourceBundle to be used for localizing messages for this logger. May be null if none of the messages require localization.
Return
Logger a newly created private Logger
Exceptions
java.util.MissingResourceException if the resourceBundleName is non-null and no corresponding resource can be found.

getFilter

Added in API level 1
open fun getFilter(): Filter?

Get the current filter for this Logger.

Return
Filter? a filter object (may be null)

getGlobal

Added in API level 19
static fun getGlobal(): Logger

Return global logger object with the name Logger.GLOBAL_LOGGER_NAME.

Return
Logger global logger object

getHandlers

Added in API level 1
open fun getHandlers(): Array<Handler!>

Get the Handlers associated with this logger.

Return
Array<Handler!> an array of all registered Handlers

getLevel

Added in API level 1
open fun getLevel(): Level?

Get the log Level that has been specified for this Logger. The result may be null, which means that this logger's effective level will be inherited from its parent.

Return
Level? this Logger's level

getLogger

Added in API level 1
open static fun getLogger(name: String): Logger

Find or create a logger for a named subsystem. If a logger has already been created with the given name it is returned. Otherwise a new logger is created.

If a new logger is created its log level will be configured based on the LogManager configuration and it will configured to also send logging output to its parent's Handlers. It will be registered in the LogManager global namespace.

Note: The LogManager may only retain a weak reference to the newly created Logger. It is important to understand that a previously created Logger with the given name may be garbage collected at any time if there is no strong reference to the Logger. In particular, this means that two back-to-back calls like getLogger("MyLogger").log(...) may use different Logger objects named "MyLogger" if there is no strong reference to the Logger named "MyLogger" elsewhere in the program.

Parameters
name String: A name for the logger. This should be a dot-separated name and should normally be based on the package name or class name of the subsystem, such as java.net or javax.swing
Return
Logger a suitable Logger
Exceptions
java.lang.NullPointerException if the name is null.

getLogger

Added in API level 1
open static fun getLogger(
    name: String, 
    resourceBundleName: String?
): Logger

Find or create a logger for a named subsystem. If a logger has already been created with the given name it is returned. Otherwise a new logger is created.

If a new logger is created its log level will be configured based on the LogManager and it will configured to also send logging output to its parent's Handlers. It will be registered in the LogManager global namespace.

Note: The LogManager may only retain a weak reference to the newly created Logger. It is important to understand that a previously created Logger with the given name may be garbage collected at any time if there is no strong reference to the Logger. In particular, this means that two back-to-back calls like getLogger("MyLogger", ...).log(...) may use different Logger objects named "MyLogger" if there is no strong reference to the Logger named "MyLogger" elsewhere in the program.

If the named Logger already exists and does not yet have a localization resource bundle then the given resource bundle name is used. If the named Logger already exists and has a different resource bundle name then an IllegalArgumentException is thrown.

Parameters
name String: A name for the logger. This should be a dot-separated name and should normally be based on the package name or class name of the subsystem, such as java.net or javax.swing
resourceBundleName String?: name of ResourceBundle to be used for localizing messages for this logger. May be null if none of the messages require localization.
Return
Logger a suitable Logger
Exceptions
java.util.MissingResourceException if the resourceBundleName is non-null and no corresponding resource can be found.
java.lang.IllegalArgumentException if the Logger already exists and uses a different resource bundle name; or if resourceBundleName is null but the named logger has a resource bundle set.
java.lang.NullPointerException if the name is null.

getName

Added in API level 1
open fun getName(): String?

Get the name for this logger.

Return
String? logger name. Will be null for anonymous Loggers.

getParent

Added in API level 1
open fun getParent(): Logger?

Return the parent for this Logger.

This method returns the nearest extant parent in the namespace. Thus if a Logger is called "a.b.c.d", and a Logger called "a.b" has been created but no logger "a.b.c" exists, then a call of getParent on the Logger "a.b.c.d" will return the Logger "a.b".

The result will be null if it is called on the root Logger in the namespace.

Return
Logger? nearest existing parent Logger

getResourceBundle

Added in API level 1
open fun getResourceBundle(): ResourceBundle?

Retrieve the localization resource bundle for this logger. This method will return a ResourceBundle that was either set by the setResourceBundle method or mapped from the the resource bundle name set via the getLogger factory method for the current default locale.
Note that if the result is null, then the Logger will use a resource bundle or resource bundle name inherited from its parent.

Return
ResourceBundle? localization bundle (may be null)

getResourceBundleName

Added in API level 1
open fun getResourceBundleName(): String?

Retrieve the localization resource bundle name for this logger. This is either the name specified through the getLogger factory method, or the base name of the ResourceBundle set through setResourceBundle method.
Note that if the result is null, then the Logger will use a resource bundle or resource bundle name inherited from its parent.

Return
String? localization bundle name (may be null)

getUseParentHandlers

Added in API level 1
open fun getUseParentHandlers(): Boolean

Discover whether or not this logger is sending its output to its parent logger.

Return
Boolean true if output is to be sent to the logger's parent

info

Added in API level 1
open fun info(msg: String?): Unit

Log an INFO message.

If the logger is currently enabled for the INFO message level then the given message is forwarded to all the registered output Handler objects.

Parameters
msg String?: The string message (or a key in the message catalog)

info

Added in API level 26
open fun info(msgSupplier: Supplier<String!>): Unit

Log a INFO message, which is only to be constructed if the logging level is such that the message will actually be logged.

If the logger is currently enabled for the INFO message level then the message is constructed by invoking the provided supplier function and forwarded to all the registered output Handler objects.

Parameters
msgSupplier Supplier<String!>: A function, which when called, produces the desired log message

isLoggable

Added in API level 1
open fun isLoggable(level: Level): Boolean

Check if a message of the given level would actually be logged by this logger. This check is based on the Loggers effective level, which may be inherited from its parent.

Parameters
level Level: a message logging level
Return
Boolean true if the given message level is currently being logged.

log

Added in API level 1
open fun log(
    level: Level, 
    msg: String?
): Unit

Log a message, with no arguments.

If the logger is currently enabled for the given message level then the given message is forwarded to all the registered output Handler objects.

Parameters
level Level: One of the message level identifiers, e.g., SEVERE
msg String?: The string message (or a key in the message catalog)

log

Added in API level 1
open fun log(
    level: Level, 
    msg: String?, 
    param1: Any?
): Unit

Log a message, with one object parameter.

If the logger is currently enabled for the given message level then a corresponding LogRecord is created and forwarded to all the registered output Handler objects.

Parameters
level Level: One of the message level identifiers, e.g., SEVERE
msg String?: The string message (or a key in the message catalog)
param1 Any?: parameter to the message

log

Added in API level 1
open fun log(
    level: Level, 
    msg: String?, 
    params: Array<Any!>?
): Unit

Log a message, with an array of object arguments.

If the logger is currently enabled for the given message level then a corresponding LogRecord is created and forwarded to all the registered output Handler objects.

Parameters
level Level: One of the message level identifiers, e.g., SEVERE
msg String?: The string message (or a key in the message catalog)
params Array<Any!>?: array of parameters to the message

log

Added in API level 1
open fun log(
    level: Level, 
    msg: String?, 
    thrown: Throwable?
): Unit

Log a message, with associated Throwable information.

If the logger is currently enabled for the given message level then the given arguments are stored in a LogRecord which is forwarded to all registered output handlers.

Note that the thrown argument is stored in the LogRecord thrown property, rather than the LogRecord parameters property. Thus it is processed specially by output Formatters and is not treated as a formatting parameter to the LogRecord message property.

Parameters
level Level: One of the message level identifiers, e.g., SEVERE
msg String?: The string message (or a key in the message catalog)
thrown Throwable?: Throwable associated with log message.

log

Added in API level 26
open fun log(
    level: Level, 
    thrown: Throwable?, 
    msgSupplier: Supplier<String!>
): Unit

Log a lazily constructed message, with associated Throwable information.

If the logger is currently enabled for the given message level then the message is constructed by invoking the provided supplier function. The message and the given Throwable are then stored in a LogRecord which is forwarded to all registered output handlers.

Note that the thrown argument is stored in the LogRecord thrown property, rather than the LogRecord parameters property. Thus it is processed specially by output Formatters and is not treated as a formatting parameter to the LogRecord message property.

Parameters
level Level: One of the message level identifiers, e.g., SEVERE
thrown Throwable?: Throwable associated with log message.
msgSupplier Supplier<String!>: A function, which when called, produces the desired log message

log

Added in API level 26
open fun log(
    level: Level, 
    msgSupplier: Supplier<String!>
): Unit

Log a message, which is only to be constructed if the logging level is such that the message will actually be logged.

If the logger is currently enabled for the given message level then the message is constructed by invoking the provided supplier function and forwarded to all the registered output Handler objects.

Parameters
level Level: One of the message level identifiers, e.g., SEVERE
msgSupplier Supplier<String!>: A function, which when called, produces the desired log message

log

Added in API level 1
open fun log(record: LogRecord): Unit

Log a LogRecord.

All the other logging methods in this class call through this method to actually perform any logging. Subclasses can override this single method to capture all log activity.

Parameters
record LogRecord: the LogRecord to be published

logp

Added in API level 1
open fun logp(
    level: Level, 
    sourceClass: String?, 
    sourceMethod: String?, 
    msg: String?
): Unit

Log a message, specifying source class and method, with no arguments.

If the logger is currently enabled for the given message level then the given message is forwarded to all the registered output Handler objects.

Parameters
level Level: One of the message level identifiers, e.g., SEVERE
sourceClass String?: name of class that issued the logging request
sourceMethod String?: name of method that issued the logging request
msg String?: The string message (or a key in the message catalog)

logp

Added in API level 1
open fun logp(
    level: Level, 
    sourceClass: String?, 
    sourceMethod: String?, 
    msg: String?, 
    param1: Any?
): Unit

Log a message, specifying source class and method, with a single object parameter to the log message.

If the logger is currently enabled for the given message level then a corresponding LogRecord is created and forwarded to all the registered output Handler objects.

Parameters
level Level: One of the message level identifiers, e.g., SEVERE
sourceClass String?: name of class that issued the logging request
sourceMethod String?: name of method that issued the logging request
msg String?: The string message (or a key in the message catalog)
param1 Any?: Parameter to the log message.

logp

Added in API level 1
open fun logp(
    level: Level, 
    sourceClass: String?, 
    sourceMethod: String?, 
    msg: String?, 
    params: Array<Any!>?
): Unit

Log a message, specifying source class and method, with an array of object arguments.

If the logger is currently enabled for the given message level then a corresponding LogRecord is created and forwarded to all the registered output Handler objects.

Parameters
level Level: One of the message level identifiers, e.g., SEVERE
sourceClass String?: name of class that issued the logging request
sourceMethod String?: name of method that issued the logging request
msg String?: The string message (or a key in the message catalog)
params Array<Any!>?: Array of parameters to the message

logp

Added in API level 1
open fun logp(
    level: Level, 
    sourceClass: String?, 
    sourceMethod: String?, 
    msg: String?, 
    thrown: Throwable?
): Unit

Log a message, specifying source class and method, with associated Throwable information.

If the logger is currently enabled for the given message level then the given arguments are stored in a LogRecord which is forwarded to all registered output handlers.

Note that the thrown argument is stored in the LogRecord thrown property, rather than the LogRecord parameters property. Thus it is processed specially by output Formatters and is not treated as a formatting parameter to the LogRecord message property.

Parameters
level Level: One of the message level identifiers, e.g., SEVERE
sourceClass String?: name of class that issued the logging request
sourceMethod String?: name of method that issued the logging request
msg String?: The string message (or a key in the message catalog)
thrown Throwable?: Throwable associated with log message.

logp

Added in API level 26
open fun logp(
    level: Level, 
    sourceClass: String?, 
    sourceMethod: String?, 
    thrown: Throwable?, 
    msgSupplier: Supplier<String!>
): Unit

Log a lazily constructed message, specifying source class and method, with associated Throwable information.

If the logger is currently enabled for the given message level then the message is constructed by invoking the provided supplier function. The message and the given Throwable are then stored in a LogRecord which is forwarded to all registered output handlers.

Note that the thrown argument is stored in the LogRecord thrown property, rather than the LogRecord parameters property. Thus it is processed specially by output Formatters and is not treated as a formatting parameter to the LogRecord message property.

Parameters
level Level: One of the message level identifiers, e.g., SEVERE
sourceClass String?: name of class that issued the logging request
sourceMethod String?: name of method that issued the logging request
thrown Throwable?: Throwable associated with log message.
msgSupplier Supplier<String!>: A function, which when called, produces the desired log message

logp

Added in API level 26
open fun logp(
    level: Level, 
    sourceClass: String?, 
    sourceMethod: String?, 
    msgSupplier: Supplier<String!>
): Unit

Log a lazily constructed message, specifying source class and method, with no arguments.

If the logger is currently enabled for the given message level then the message is constructed by invoking the provided supplier function and forwarded to all the registered output Handler objects.

Parameters
level Level: One of the message level identifiers, e.g., SEVERE
sourceClass String?: name of class that issued the logging request
sourceMethod String?: name of method that issued the logging request
msgSupplier Supplier<String!>: A function, which when called, produces the desired log message

logrb

Added in API level 1
Deprecated in API level 26
open fun logrb(
    level: Level, 
    sourceClass: String?, 
    sourceMethod: String?, 
    bundleName: String?, 
    msg: String?
): Unit

Deprecated: Use logrb(java.util.logging.Level,java.lang.String,java.lang.String,java.util.ResourceBundle,java.lang.String,java.lang.Object...) instead.

Log a message, specifying source class, method, and resource bundle name with no arguments.

If the logger is currently enabled for the given message level then the given message is forwarded to all the registered output Handler objects.

The msg string is localized using the named resource bundle. If the resource bundle name is null, or an empty String or invalid then the msg string is not localized.

Parameters
level Level: One of the message level identifiers, e.g., SEVERE
sourceClass String?: name of class that issued the logging request
sourceMethod String?: name of method that issued the logging request
bundleName String?: name of resource bundle to localize msg, can be null
msg String?: The string message (or a key in the message catalog)

logrb

Added in API level 1
Deprecated in API level 26
open fun logrb(
    level: Level, 
    sourceClass: String?, 
    sourceMethod: String?, 
    bundleName: String?, 
    msg: String?, 
    param1: Any?
): Unit

Deprecated: Use logrb(java.util.logging.Level,java.lang.String,java.lang.String,java.util.ResourceBundle,java.lang.String,java.lang.Object...) instead

Log a message, specifying source class, method, and resource bundle name, with a single object parameter to the log message.

If the logger is currently enabled for the given message level then a corresponding LogRecord is created and forwarded to all the registered output Handler objects.

The msg string is localized using the named resource bundle. If the resource bundle name is null, or an empty String or invalid then the msg string is not localized.

Parameters
level Level: One of the message level identifiers, e.g., SEVERE
sourceClass String?: name of class that issued the logging request
sourceMethod String?: name of method that issued the logging request
bundleName String?: name of resource bundle to localize msg, can be null
msg String?: The string message (or a key in the message catalog)
param1 Any?: Parameter to the log message.

logrb

Added in API level 1
Deprecated in API level 26
open fun logrb(
    level: Level, 
    sourceClass: String?, 
    sourceMethod: String?, 
    bundleName: String?, 
    msg: String?, 
    params: Array<Any!>?
): Unit

Deprecated: Use logrb(java.util.logging.Level,java.lang.String,java.lang.String,java.util.ResourceBundle,java.lang.String,java.lang.Object...) instead.

Log a message, specifying source class, method, and resource bundle name, with an array of object arguments.

If the logger is currently enabled for the given message level then a corresponding LogRecord is created and forwarded to all the registered output Handler objects.

The msg string is localized using the named resource bundle. If the resource bundle name is null, or an empty String or invalid then the msg string is not localized.

Parameters
level Level: One of the message level identifiers, e.g., SEVERE
sourceClass String?: name of class that issued the logging request
sourceMethod String?: name of method that issued the logging request
bundleName String?: name of resource bundle to localize msg, can be null.
msg String?: The string message (or a key in the message catalog)
params Array<Any!>?: Array of parameters to the message

logrb

Added in API level 1
Deprecated in API level 26
open fun logrb(
    level: Level, 
    sourceClass: String?, 
    sourceMethod: String?, 
    bundleName: String?, 
    msg: String?, 
    thrown: Throwable?
): Unit

Deprecated: Use logrb(java.util.logging.Level,java.lang.String,java.lang.String,java.util.ResourceBundle,java.lang.String,java.lang.Throwable) instead.

Log a message, specifying source class, method, and resource bundle name, with associated Throwable information.

If the logger is currently enabled for the given message level then the given arguments are stored in a LogRecord which is forwarded to all registered output handlers.

The msg string is localized using the named resource bundle. If the resource bundle name is null, or an empty String or invalid then the msg string is not localized.

Note that the thrown argument is stored in the LogRecord thrown property, rather than the LogRecord parameters property. Thus it is processed specially by output Formatters and is not treated as a formatting parameter to the LogRecord message property.

Parameters
level Level: One of the message level identifiers, e.g., SEVERE
sourceClass String?: name of class that issued the logging request
sourceMethod String?: name of method that issued the logging request
bundleName String?: name of resource bundle to localize msg, can be null
msg String?: The string message (or a key in the message catalog)
thrown Throwable?: Throwable associated with log message.

logrb

Added in API level 26
open fun logrb(
    level: Level, 
    sourceClass: String?, 
    sourceMethod: String?, 
    bundle: ResourceBundle?, 
    msg: String?, 
    vararg params: Any!
): Unit

Log a message, specifying source class, method, and resource bundle, with an optional list of message parameters.

If the logger is currently enabled for the given message level then a corresponding LogRecord is created and forwarded to all the registered output Handler objects.

The msg string is localized using the given resource bundle. If the resource bundle is null, then the msg string is not localized.

Parameters
level Level: One of the message level identifiers, e.g., SEVERE
sourceClass String?: Name of the class that issued the logging request
sourceMethod String?: Name of the method that issued the logging request
bundle ResourceBundle?: Resource bundle to localize msg, can be null.
msg String?: The string message (or a key in the message catalog)
params Any!: Parameters to the message (optional, may be none).

logrb

Added in API level 26
open fun logrb(
    level: Level, 
    sourceClass: String?, 
    sourceMethod: String?, 
    bundle: ResourceBundle?, 
    msg: String?, 
    thrown: Throwable?
): Unit

Log a message, specifying source class, method, and resource bundle, with associated Throwable information.

If the logger is currently enabled for the given message level then the given arguments are stored in a LogRecord which is forwarded to all registered output handlers.

The msg string is localized using the given resource bundle. If the resource bundle is null, then the msg string is not localized.

Note that the thrown argument is stored in the LogRecord thrown property, rather than the LogRecord parameters property. Thus it is processed specially by output Formatters and is not treated as a formatting parameter to the LogRecord message property.

Parameters
level Level: One of the message level identifiers, e.g., SEVERE
sourceClass String?: Name of the class that issued the logging request
sourceMethod String?: Name of the method that issued the logging request
bundle ResourceBundle?: Resource bundle to localize msg, can be null
msg String?: The string message (or a key in the message catalog)
thrown Throwable?: Throwable associated with the log message.

removeHandler

Added in API level 1
open fun removeHandler(handler: Handler?): Unit

Remove a log Handler.

Returns silently if the given Handler is not found or is null

Parameters
handler Handler?: a logging Handler
Exceptions
java.lang.SecurityException if a security manager exists, this logger is not anonymous, and the caller does not have LoggingPermission("control").

setFilter

Added in API level 1
open fun setFilter(newFilter: Filter?): Unit

Set a filter to control output on this Logger.

After passing the initial "level" check, the Logger will call this Filter to check if a log record should really be published.

Parameters
newFilter Filter?: a filter object (may be null)
Exceptions
java.lang.SecurityException if a security manager exists, this logger is not anonymous, and the caller does not have LoggingPermission("control").

setLevel

Added in API level 1
open fun setLevel(newLevel: Level?): Unit

Set the log level specifying which message levels will be logged by this logger. Message levels lower than this value will be discarded. The level value Level.OFF can be used to turn off logging.

If the new level is null, it means that this node should inherit its level from its nearest ancestor with a specific (non-null) level value.

Parameters
newLevel Level?: the new value for the log level (may be null)
Exceptions
java.lang.SecurityException if a security manager exists, this logger is not anonymous, and the caller does not have LoggingPermission("control").

setParent

Added in API level 1
open fun setParent(parent: Logger): Unit

Set the parent for this Logger. This method is used by the LogManager to update a Logger when the namespace changes.

It should not be called from application code.

Parameters
parent Logger: the new parent logger
Exceptions
java.lang.SecurityException if a security manager exists and if the caller does not have LoggingPermission("control").

setResourceBundle

Added in API level 26
open fun setResourceBundle(bundle: ResourceBundle): Unit

Sets a resource bundle on this logger. All messages will be logged using the given resource bundle for its specific locale.

Parameters
bundle ResourceBundle: The resource bundle that this logger shall use.
Exceptions
java.lang.NullPointerException if the given bundle is null.
java.lang.IllegalArgumentException if the given bundle doesn't have a base name, or if this logger already has a resource bundle set but the given bundle has a different base name.
java.lang.SecurityException if a security manager exists, this logger is not anonymous, and the caller does not have LoggingPermission("control").

setUseParentHandlers

Added in API level 1
open fun setUseParentHandlers(useParentHandlers: Boolean): Unit

Specify whether or not this logger should send its output to its parent Logger. This means that any LogRecords will also be written to the parent's Handlers, and potentially to its parent, recursively up the namespace.

Parameters
useParentHandlers Boolean: true if output is to be sent to the logger's parent.
Exceptions
java.lang.SecurityException if a security manager exists, this logger is not anonymous, and the caller does not have LoggingPermission("control").

severe

Added in API level 1
open fun severe(msg: String?): Unit

Log a SEVERE message.

If the logger is currently enabled for the SEVERE message level then the given message is forwarded to all the registered output Handler objects.

Parameters
msg String?: The string message (or a key in the message catalog)

severe

Added in API level 26
open fun severe(msgSupplier: Supplier<String!>): Unit

Log a SEVERE message, which is only to be constructed if the logging level is such that the message will actually be logged.

If the logger is currently enabled for the SEVERE message level then the message is constructed by invoking the provided supplier function and forwarded to all the registered output Handler objects.

Parameters
msgSupplier Supplier<String!>: A function, which when called, produces the desired log message

throwing

Added in API level 1
open fun throwing(
    sourceClass: String?, 
    sourceMethod: String?, 
    thrown: Throwable?
): Unit

Log throwing an exception.

This is a convenience method to log that a method is terminating by throwing an exception. The logging is done using the FINER level.

If the logger is currently enabled for the given message level then the given arguments are stored in a LogRecord which is forwarded to all registered output handlers. The LogRecord's message is set to "THROW".

Note that the thrown argument is stored in the LogRecord thrown property, rather than the LogRecord parameters property. Thus it is processed specially by output Formatters and is not treated as a formatting parameter to the LogRecord message property.

Parameters
sourceClass String?: name of class that issued the logging request
sourceMethod String?: name of the method.
thrown Throwable?: The Throwable that is being thrown.

warning

Added in API level 1
open fun warning(msg: String?): Unit

Log a WARNING message.

If the logger is currently enabled for the WARNING message level then the given message is forwarded to all the registered output Handler objects.

Parameters
msg String?: The string message (or a key in the message catalog)

warning

Added in API level 26
open fun warning(msgSupplier: Supplier<String!>): Unit

Log a WARNING message, which is only to be constructed if the logging level is such that the message will actually be logged.

If the logger is currently enabled for the WARNING message level then the message is constructed by invoking the provided supplier function and forwarded to all the registered output Handler objects.

Parameters
msgSupplier Supplier<String!>: A function, which when called, produces the desired log message

Properties

global

Added in API level 1
Deprecated in API level 15
static val global: Logger

Deprecated: Initialization of this field is prone to deadlocks. The field must be initialized by the Logger class initialization which may cause deadlocks with the LogManager class initialization. In such cases two class initialization wait for each other to complete. The preferred way to get the global logger object is via the call Logger.getGlobal(). For compatibility with old JDK versions where the Logger.getGlobal() is not available use the call Logger.getLogger(Logger.GLOBAL_LOGGER_NAME) or Logger.getLogger("global").

The "global" Logger object is provided as a convenience to developers who are making casual use of the Logging package. Developers who are making serious use of the logging package (for example in products) should create and use their own Logger objects, with appropriate names, so that logging can be controlled on a suitable per-Logger granularity. Developers also need to keep a strong reference to their Logger objects to prevent them from being garbage collected.