119 lines
6.2 KiB
Java
119 lines
6.2 KiB
Java
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/*
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* Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/**
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* Provides the classes and interfaces of
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* the Java 2 platform's core logging facilities.
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* The central goal of the logging APIs is to support maintaining and servicing
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* software at customer sites.
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*
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* <P>
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* There are four main target uses of the logs:
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* </P>
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*
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* <OL>
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* <LI> <I>Problem diagnosis by end users and system administrators</I>.
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* This consists of simple logging of common problems that can be fixed
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* or tracked locally, such as running out of resources, security failures,
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* and simple configuration errors.
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*
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* <LI> <I>Problem diagnosis by field service engineers</I>. The logging information
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* used by field service engineers may be considerably more complex and
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* verbose than that required by system administrators. Typically such information
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* will require extra logging within particular subsystems.
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*
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* <LI> <I>Problem diagnosis by the development organization</I>.
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* When a problem occurs in the field, it may be necessary to return the captured logging
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* information to the original development team for diagnosis. This logging
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* information may be extremely detailed and fairly inscrutable. Such information might include
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* detailed tracing on the internal execution of particular subsystems.
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*
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* <LI> <I>Problem diagnosis by developers</I>. The Logging APIs may also be
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* used to help debug an application under development. This may
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* include logging information generated by the target application
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* as well as logging information generated by lower-level libraries.
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* Note however that while this use is perfectly reasonable,
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* the logging APIs are not intended to replace the normal debugging
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* and profiling tools that may already exist in the development environment.
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* </OL>
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*
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* <p>
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* The key elements of this package include:
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* <UL>
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* <LI> <I>Logger</I>: The main entity on which applications make
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* logging calls. A Logger object is used to log messages
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* for a specific system or application
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* component.
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* <LI> <I>LogRecord</I>: Used to pass logging requests between the logging
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* framework and individual log handlers.
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* <LI> <I>Handler</I>: Exports LogRecord objects to a variety of destinations
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* including memory, output streams, consoles, files, and sockets.
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* A variety of Handler subclasses exist for this purpose. Additional Handlers
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* may be developed by third parties and delivered on top of the core platform.
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* <LI> <I>Level</I>: Defines a set of standard logging levels that can be used
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* to control logging output. Programs can be configured to output logging
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* for some levels while ignoring output for others.
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* <LI> <I>Filter</I>: Provides fine-grained control over what gets logged,
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* beyond the control provided by log levels. The logging APIs support a general-purpose
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* filter mechanism that allows application code to attach arbitrary filters to
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* control logging output.
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*
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* <LI> <I>Formatter</I>: Provides support for formatting LogRecord objects. This
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* package includes two formatters, SimpleFormatter and
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* XMLFormatter, for formatting log records in plain text
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* or XML respectively. As with Handlers, additional Formatters
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* may be developed by third parties.
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* </UL>
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* <P>
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* The Logging APIs offer both static and dynamic configuration control.
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* Static control enables field service staff to set up a particular configuration and then re-launch the
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* application with the new logging settings. Dynamic control allows for updates to the
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* logging configuration within a currently running program. The APIs also allow for logging to be
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* enabled or disabled for different functional areas of the system. For example,
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* a field service engineer might be interested in tracing all AWT events, but might have no interest in
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* socket events or memory management.
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* </P>
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*
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* <h2>Null Pointers</h2>
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* <p>
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* In general, unless otherwise noted in the javadoc, methods and
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* constructors will throw NullPointerException if passed a null argument.
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* The one broad exception to this rule is that the logging convenience
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* methods in the Logger class (the config, entering, exiting, fine, finer, finest,
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* log, logp, logrb, severe, throwing, and warning methods)
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* will accept null values
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* for all arguments except for the initial Level argument (if any).
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*
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* <H2>Related Documentation</H2>
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* <P>
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* For an overview of control flow,
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* please refer to the
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* <a href="https://docs.oracle.com/pls/topic/lookup?ctx=javase17&id=logging_overview">Java Logging Overview</a>
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* </P>
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*
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* @since 1.4
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*/
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package java.util.logging;
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