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| 1 | +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> | |
| 2 | +<html> | |
| 3 | +<head> | |
| 4 | +<!-- | |
| 5 | +Copyright (c) 2001, 2006, Oracle and/or its affiliates. All rights reserved. | |
| 6 | +DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | |
| 7 | + | |
| 8 | +This code is free software; you can redistribute it and/or modify it | |
| 9 | +under the terms of the GNU General Public License version 2 only, as | |
| 10 | +published by the Free Software Foundation. Oracle designates this | |
| 11 | +particular file as subject to the "Classpath" exception as provided | |
| 12 | +by Oracle in the LICENSE file that accompanied this code. | |
| 13 | + | |
| 14 | +This code is distributed in the hope that it will be useful, but WITHOUT | |
| 15 | +ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 16 | +FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 17 | +version 2 for more details (a copy is included in the LICENSE file that | |
| 18 | +accompanied this code). | |
| 19 | + | |
| 20 | +You should have received a copy of the GNU General Public License version | |
| 21 | +2 along with this work; if not, write to the Free Software Foundation, | |
| 22 | +Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
| 23 | + | |
| 24 | +Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | |
| 25 | +or visit www.oracle.com if you need additional information or have any | |
| 26 | +questions. | |
| 27 | +--> | |
| 28 | + | |
| 29 | +</head> | |
| 30 | +<body bgcolor="white"> | |
| 31 | +<P> | |
| 32 | +Provides the classes and interfaces of | |
| 33 | +the Java<SUP><FONT SIZE="-2">TM</FONT></SUP> 2 | |
| 34 | + platform's core logging facilities. | |
| 35 | +The central goal of the logging APIs is to support maintaining and servicing | |
| 36 | +software at customer sites. | |
| 37 | + | |
| 38 | +<P> | |
| 39 | +There are four main target uses of the logs: | |
| 40 | +</P> | |
| 41 | + | |
| 42 | +<OL> | |
| 43 | + <LI> <I>Problem diagnosis by end users and system administrators</I>. | |
| 44 | + This consists of simple logging of common problems that can be fixed | |
| 45 | + or tracked locally, such as running out of resources, security failures, | |
| 46 | + and simple configuration errors. | |
| 47 | + | |
| 48 | + <LI> <I>Problem diagnosis by field service engineers</I>. The logging information | |
| 49 | + used by field service engineers may be considerably more complex and | |
| 50 | + verbose than that required by system administrators. Typically such information | |
| 51 | + will require extra logging within particular subsystems. | |
| 52 | + | |
| 53 | + <LI> <I>Problem diagnosis by the development organization</I>. | |
| 54 | + When a problem occurs in the field, it may be necessary to return the captured logging | |
| 55 | + information to the original development team for diagnosis. This logging | |
| 56 | + information may be extremely detailed and fairly inscrutable. Such information might include | |
| 57 | + detailed tracing on the internal execution of particular subsystems. | |
| 58 | + | |
| 59 | + <LI> <I>Problem diagnosis by developers</I>. The Logging APIs may also be | |
| 60 | + used to help debug an application under development. This may | |
| 61 | + include logging information generated by the target application | |
| 62 | + as well as logging information generated by lower-level libraries. | |
| 63 | + Note however that while this use is perfectly reasonable, | |
| 64 | + the logging APIs are not intended to replace the normal debugging | |
| 65 | + and profiling tools that may already exist in the development environment. | |
| 66 | +</OL> | |
| 67 | + | |
| 68 | +</P> | |
| 69 | +The key elements of this package include: | |
| 70 | +<UL> | |
| 71 | + <LI> <I>Logger</I>: The main entity on which applications make | |
| 72 | + logging calls. A Logger object is used to log messages | |
| 73 | + for a specific system or application | |
| 74 | + component. | |
| 75 | + <LI> <I>LogRecord</I>: Used to pass logging requests between the logging | |
| 76 | + framework and individual log handlers. | |
| 77 | + <LI> <I>Handler</I>: Exports LogRecord objects to a variety of destinations | |
| 78 | + including memory, output streams, consoles, files, and sockets. | |
| 79 | + A variety of Handler subclasses exist for this purpose. Additional Handlers | |
| 80 | + may be developed by third parties and delivered on top of the core platform. | |
| 81 | + <LI> <I>Level</I>: Defines a set of standard logging levels that can be used | |
| 82 | + to control logging output. Programs can be configured to output logging | |
| 83 | + for some levels while ignoring output for others. | |
| 84 | + <LI> <I>Filter</I>: Provides fine-grained control over what gets logged, | |
| 85 | + beyond the control provided by log levels. The logging APIs support a general-purpose | |
| 86 | + filter mechanism that allows application code to attach arbitrary filters to | |
| 87 | + control logging output. | |
| 88 | + | |
| 89 | + <LI> <I>Formatter</I>: Provides support for formatting LogRecord objects. This | |
| 90 | + package includes two formatters, SimpleFormatter and | |
| 91 | + XMLFormatter, for formatting log records in plain text | |
| 92 | + or XML respectively. As with Handlers, additional Formatters | |
| 93 | + may be developed by third parties. | |
| 94 | +</UL> | |
| 95 | +<P> | |
| 96 | +The Logging APIs offer both static and dynamic configuration control. | |
| 97 | +Static control enables field service staff to set up a particular configuration and then re-launch the | |
| 98 | +application with the new logging settings. Dynamic control allows for updates to the | |
| 99 | +logging configuration within a currently running program. The APIs also allow for logging to be | |
| 100 | +enabled or disabled for different functional areas of the system. For example, | |
| 101 | +a field service engineer might be interested in tracing all AWT events, but might have no interest in | |
| 102 | +socket events or memory management. | |
| 103 | +</P> | |
| 104 | + | |
| 105 | +<h2>Null Pointers</h2> | |
| 106 | +<p> | |
| 107 | +In general, unless otherwise noted in the javadoc, methods and | |
| 108 | +constructors will throw NullPointerException if passed a null argument. | |
| 109 | +The one broad exception to this rule is that the logging convenience | |
| 110 | +methods in the Logger class (the config, entering, exiting, fine, finer, finest, | |
| 111 | +log, logp, logrb, severe, throwing, and warning methods) | |
| 112 | +will accept null values | |
| 113 | +for all arguments except for the initial Level argument (if any). | |
| 114 | +<p> | |
| 115 | +<H2>Related Documentation</H2> | |
| 116 | +<P> | |
| 117 | +For an overview of control flow, | |
| 118 | +please refer to the | |
| 119 | +<a href="../../../../technotes/guides/logging/overview.html"> | |
| 120 | +Java Logging Overview</a>. | |
| 121 | +</P> | |
| 122 | + | |
| 123 | +<!-- Put @see and @since tags down here. --> | |
| 124 | + | |
| 125 | +@since 1.4 | |
| 126 | + | |
| 127 | + | |
| 128 | +</body> | |
| 129 | +</html> | |
| 130 | + | |
| 131 | + | |
| 132 | + | |
| 133 | + | |
| 134 | + | |