/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements.  See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License.  You may obtain a copy of the License at *  *      http://www.apache.org/licenses/LICENSE-2.0 *  * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package org.apache.log4j;import org.apache.log4j.Layout;import org.apache.log4j.spi.LoggingEvent;import org.apache.log4j.helpers.PatternParser;import org.apache.log4j.helpers.PatternConverter;// Contributors:   Nelson Minar <nelson@monkey.org>//                 Anders Kristensen <akristensen@dynamicsoft.com>/**   A flexible layout configurable with pattern string.   <p>The goal of this class is to {@link #format format} a {@link   LoggingEvent} and return the results as a String. The results   depend on the <em>conversion pattern</em>.   <p>The conversion pattern is closely related to the conversion   pattern of the printf function in C. A conversion pattern is   composed of literal text and format control expressions called   <em>conversion specifiers</em>.   <p><i>You are free to insert any literal text within the conversion   pattern.</i>   <p>Each conversion specifier starts with a percent sign (%) and is   followed by optional <em>format modifiers</em> and a <em>conversion   character</em>. The conversion character specifies the type of   data, e.g. category, priority, date, thread name. The format   modifiers control such things as field width, padding, left and   right justification. The following is a simple example.   <p>Let the conversion pattern be <b>"%-5p [%t]: %m%n"</b> and assume   that the log4j environment was set to use a PatternLayout. Then the   statements   <pre>   Category root = Category.getRoot();   root.debug("Message 1");   root.warn("Message 2");   </pre>   would yield the output   <pre>   DEBUG [main]: Message 1   WARN  [main]: Message 2   </pre>   <p>Note that there is no explicit separator between text and   conversion specifiers. The pattern parser knows when it has reached   the end of a conversion specifier when it reads a conversion   character. In the example above the conversion specifier   <b>%-5p</b> means the priority of the logging event should be left   justified to a width of five characters.   The recognized conversion characters are   <p>   <table border="1" CELLPADDING="8">   <th>Conversion Character</th>   <th>Effect</th>   <tr>     <td align=center><b>c</b></td>     <td>Used to output the category of the logging event. The     category conversion specifier can be optionally followed by     <em>precision specifier</em>, that is a decimal constant in     brackets.     <p>If a precision specifier is given, then only the corresponding     number of right most components of the category name will be     printed. By default the category name is printed in full.     <p>For example, for the category name "a.b.c" the pattern     <b>%c{2}</b> will output "b.c".     </td>   </tr>   <tr>     <td align=center><b>C</b></td>     <td>Used to output the fully qualified class name of the caller     issuing the logging request. This conversion specifier     can be optionally followed by <em>precision specifier</em>, that     is a decimal constant in brackets.     <p>If a precision specifier is given, then only the corresponding     number of right most components of the class name will be     printed. By default the class name is output in fully qualified form.     <p>For example, for the class name "org.apache.xyz.SomeClass", the     pattern <b>%C{1}</b> will output "SomeClass".     <p><b>WARNING</b> Generating the caller class information is     slow. Thus, it's use should be avoided unless execution speed is     not an issue.     </td>     </tr>   <tr> <td align=center><b>d</b></td> <td>Used to output the date of	 the logging event. The date conversion specifier may be	 followed by a <em>date format specifier</em> enclosed between	 braces. For example, <b>%d{HH:mm:ss,SSS}</b> or	 <b>%d{dd&nbsp;MMM&nbsp;yyyy&nbsp;HH:mm:ss,SSS}</b>.  If no	 date format specifier is given then ISO8601 format is	 assumed.	 <p>The date format specifier admits the same syntax as the	 time pattern string of the {@link	 java.text.SimpleDateFormat}. Although part of the standard	 JDK, the performance of <code>SimpleDateFormat</code> is	 quite poor.	 <p>For better results it is recommended to use the log4j date	 formatters. These can be specified using one of the strings	 "ABSOLUTE", "DATE" and "ISO8601" for specifying {@link	 org.apache.log4j.helpers.AbsoluteTimeDateFormat	 AbsoluteTimeDateFormat}, {@link	 org.apache.log4j.helpers.DateTimeDateFormat DateTimeDateFormat}	 and respectively {@link	 org.apache.log4j.helpers.ISO8601DateFormat	 ISO8601DateFormat}. For example, <b>%d{ISO8601}</b> or	 <b>%d{ABSOLUTE}</b>.	 <p>These dedicated date formatters perform significantly	 better than {@link java.text.SimpleDateFormat}.     </td>   </tr>   <tr>   <td align=center><b>F</b></td>   <td>Used to output the file name where the logging request was   issued.   <p><b>WARNING</b> Generating caller location information is   extremely slow. It's use should be avoided unless execution speed   is not an issue.   </tr>   <tr>   <td align=center><b>l</b></td>     <td>Used to output location information of the caller which generated     the logging event.     <p>The location information depends on the JVM implementation but     usually consists of the fully qualified name of the calling     method followed by the callers source the file name and line     number between parentheses.     <p>The location information can be very useful. However, it's     generation is <em>extremely</em> slow. It's use should be avoided     unless execution speed is not an issue.     </td>   </tr>   <tr>   <td align=center><b>L</b></td>   <td>Used to output the line number from where the logging request   was issued.   <p><b>WARNING</b> Generating caller location information is   extremely slow. It's use should be avoided unless execution speed   is not an issue.   </tr>   <tr>     <td align=center><b>m</b></td>     <td>Used to output the application supplied message associated with     the logging event.</td>   </tr>   <tr>   <td align=center><b>M</b></td>   <td>Used to output the method name where the logging request was   issued.   <p><b>WARNING</b> Generating caller location information is   extremely slow. It's use should be avoided unless execution speed   is not an issue.   </tr>   <tr>     <td align=center><b>n</b></td>     <td>Outputs the platform dependent line separator character or     characters.     <p>This conversion character offers practically the same     performance as using non-portable line separator strings such as     "\n", or "\r\n". Thus, it is the preferred way of specifying a     line separator.   </tr>   <tr>     <td align=center><b>p</b></td>     <td>Used to output the priority of the logging event.</td>   </tr>   <tr>     <td align=center><b>r</b></td>     <td>Used to output the number of milliseconds elapsed from the construction      of the layout until the creation of the logging event.</td>   </tr>   <tr>     <td align=center><b>t</b></td>     <td>Used to output the name of the thread that generated the     logging event.</td>   </tr>   <tr>     <td align=center><b>x</b></td>     <td>Used to output the NDC (nested diagnostic context) associated     with the thread that generated the logging event.     </td>   </tr>