| author | dfuchs |
| Thu, 06 Apr 2017 14:38:15 +0100 | |
| changeset 44538 | a603c475d649 |
| parent 32427 | c22b7e41adf3 |
| child 45136 | bd5c526bc443 |
| permissions | -rw-r--r-- |
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> |
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<html> |
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<head> |
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<!-- |
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Copyright (c) 2001, 2006, 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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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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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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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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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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</head> |
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<body bgcolor="white"> |
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<P> |
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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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<P> |
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There are four main target uses of the logs: |
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</P> |
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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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<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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<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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<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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<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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<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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<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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<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="../../../../technotes/guides/logging/overview.html"> |
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Java Logging Overview</a>. |
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</P> |
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<!-- Put @see and @since tags down here. --> |
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@since 1.4 |
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</body> |
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</html> |