src/main/java/org/apache/log4j/EnhancedPatternLayout.java - log4j-extras - Git at Google

 /*
  * 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.helpers.OptionConverter;
 import org.apache.log4j.helpers.PatternConverter;
 import org.apache.log4j.pattern.BridgePatternConverter;
 import org.apache.log4j.spi.LoggingEvent;


 // Contributors:   Nelson Minar <nelson@monkey.org>
 //                 Anders Kristensen <akristensen@dynamicsoft.com>

 /**
  * This class is an enhanced version of org.apache.log4j.PatternLayout
  * which was originally developed as part of the abandoned log4j 1.3
  * effort and has been available in the extras companion.
  * This pattern layout should be used in preference to
  * org.apache.log4j.PatternLayout except when compatibility
  * where PatternLayout has been extended either through subclassing
  * or alternative pattern parsers.
  *
  *
   * <p>A flexible layout configurable with pattern string. The goal of this class
   * is to {@link #format format} a {@link LoggingEvent} and return the results
   * in a {@link StringBuffer}. The format of the result depends on the
   * <em>conversion pattern</em>.
   * <p>
   *
   * <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>Note that you are free to insert any literal text within the
   * conversion pattern.</i>
   * </p>

    <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 EnhancedPatternLayout. 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
      NameAbbreviator pattern.

      <p>For example, for the category name "alpha.beta.gamma" the pattern
      <b>%c{2}</b> will output the last two elements ("beta.gamma"),
      <b>%c{-2}</b> will remove two elements leaving "gamma",
      <b>%c{1.}</b> will output "a.b.gamma".

      </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.

      <td>Used to output the category of the logging event. The
      category conversion specifier can be optionally followed by
      NameAbbreviator pattern.

      <p>For example, for the category name "alpha.beta.gamma" the pattern
      <b>%c{2}</b> will output the last two elements ("beta.gamma"),
      <b>%c{-2}</b> will remove two elements leaving "gamma",
      <b>%c{1.}</b> will output "a.b.gamma".

      <p><b>WARNING</b> Generating the caller class information is
      slow. Thus, its 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 set of braces containing a
          date and time pattern strings {@link java.text.SimpleDateFormat},
          <em>ABSOLUTE</em>, <em>DATE</em> or <em>ISO8601</em>
           and a set of braces containing a time zone id per
           {@link java.util.TimeZone#getTimeZone(String)}.
           For example, <b>%d{HH:mm:ss,SSS}</b>,
          <b>%d{dd&nbsp;MMM&nbsp;yyyy&nbsp;HH:mm:ss,SSS}</b>,
          <b>%d{DATE}</b> or <b>%d{HH:mm:ss}{GMT+0}</b>. If no date format specifier is given then
          ISO8601 format is assumed.
      </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 and 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, its
      generation is <em>extremely</em> slow and 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 and 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 and 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 since 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>


    <tr>
      <td align=center><b>X</b></td>

      <td>

      <p>Used to output the MDC (mapped diagnostic context) associated
      with the thread that generated the logging event. The <b>X</b>
      conversion character can be followed by the key for the
      map placed between braces, as in <b>%X{clientNumber}</b> where
      <code>clientNumber</code> is the key. The value in the MDC
      corresponding to the key will be output. If no additional sub-option
      is specified, then the entire contents of the MDC key value pair set
      is output using a format {{key1,val1},{key2,val2}}</p>

      <p>See {@link MDC} class for more details.
      </p>

      </td>
    </tr>

       <tr>
      <td align=center><b>properties</b></td>

      <td>
      <p>Used to output the Properties associated
      with the logging event. The <b>properties</b>
      conversion word can be followed by the key for the
      map placed between braces, as in <b>%properties{application}</b> where
      <code>application</code> is the key. The value in the Properties bundle
      corresponding to the key will be output. If no additional sub-option
      is specified, then the entire contents of the Properties key value pair set
      is output using a format {{key1,val1},{key2,val2}}</p>
      </td>
    </tr>

             <tr>
      <td align=center><b>throwable</b></td>

      <td>
      <p>Used to output the Throwable trace that has been bound to the LoggingEvent, by
      default this will output the full trace as one would normally
      find by a call to Throwable.printStackTrace().
      <b>%throwable{short}</b> or <b>%throwable{1}</b> will output the first line of
      stack trace.   <b>throwable{none}</b> or <b>throwable{0}</b> will suppress
      the stack trace.  <b>%throwable{n}</b> will output n lines of stack trace
      if a positive integer or omit the last -n lines if a negative integer.
      If no %throwable pattern is specified, the appender will take
      responsibility to output the stack trace as it sees fit.</p>
      </td>
    </tr>

    <tr>

      <td align=center><b>%</b></td>

      <td>The sequence %% outputs a single percent sign.
      </td>
    </tr>

    </table>

    <p>By default the relevant information is output as is. However,
    with the aid of format modifiers it is possible to change the
    minimum field width, the maximum field width, justification
    and truncation.

    <p>The optional format modifiers are placed between the percent sign
    and the conversion character.

    <p>The <em>left justification flag</em>, the minus sign (-),
     the <em>right truncation flag</em>, the exclamation mark (!),
     or any combination appear first.  Followed by the
    optional <em>minimum field width</em> modifier. This is a decimal
    constant that represents the minimum number of characters to
    output. If the data item requires fewer characters, it is padded on
    either the left or the right until the minimum width is
    reached. The default is to pad on the left (right justify) but you
    can specify right padding with the left justification flag. The
    padding character is space. If the data item is larger than the
    minimum field width, the field is expanded to accommodate the
    data. The value is never truncated.

    <p>This behavior can be changed using the <em>maximum field
    width</em> modifier which is designated by a period followed by a
    decimal constant. If the data item is longer than the maximum
    field, then the extra characters are removed from the
    <em>beginning</em> of the data item and not from the end. For
    example, it the maximum field width is eight and the data item is
    ten characters long, then the first two characters of the data item
    are dropped. This behavior deviates from the printf function in C
    where truncation is done from the end.  The <em>right truncation flag</em>,
    described previously, will override this behavior.

    <p>Below are various format modifier examples for the category
    conversion specifier.

    <p>
    <TABLE BORDER=1 CELLPADDING=8>
    <th>Format modifier
    <th>left justify
    <th>minimum width
    <th>maximum width
    <th>comment

    <tr>
    <td align=center>%20c</td>
    <td align=center>false</td>
    <td align=center>20</td>
    <td align=center>none</td>

    <td>Left pad with spaces if the category name is less than 20
    characters long.

    <tr> <td align=center>%-20c</td> <td align=center>true</td> <td
    align=center>20</td> <td align=center>none</td> <td>Right pad with
    spaces if the category name is less than 20 characters long.

    <tr>
    <td align=center>%.30c</td>
    <td align=center>NA</td>
    <td align=center>none</td>
    <td align=center>30</td>

    <td>Truncate from the beginning if the category name is longer than 30
    characters.

    <tr>
    <td align=center>%!.30c</td>
    <td align=center>NA</td>
    <td align=center>none</td>
    <td align=center>30</td>

    <td>Truncate from the end if the category name is longer than 30
    characters.

    <tr>
    <td align=center>%20.30c</td>
    <td align=center>false</td>
    <td align=center>20</td>
    <td align=center>30</td>

    <td>Left pad with spaces if the category name is shorter than 20
    characters. However, if category name is longer than 30 characters,
    then truncate from the beginning.

    <tr>
    <td align=center>%-20.30c</td>
    <td align=center>true</td>
    <td align=center>20</td>
    <td align=center>30</td>

    <td>Right pad with spaces if the category name is shorter than 20
    characters. However, if category name is longer than 30 characters,
    then truncate from the beginning.

    </table>

    <p>Below are some examples of conversion patterns.

    <dl>

    <p><dt><b>%r [%t] %-5p %c %x - %m%n</b>
    <p><dd>This is essentially the TTCC layout.

    <p><dt><b>%-6r [%15.15t] %-5p %30.30c %x - %m%n</b>

    <p><dd>Similar to the TTCC layout except that the relative time is
    right padded if less than 6 digits, thread name is right padded if
    less than 15 characters and truncated if longer and the category
    name is left padded if shorter than 30 characters and truncated if
    longer.

   </dl>

    <p>The above text is largely inspired from Peter A. Darnell and
    Philip E. Margolis' highly recommended book "C -- a Software
    Engineering Approach", ISBN 0-387-97389-3.

    @author <a href="mailto:cakalijp@Maritz.com">James P. Cakalic</a>
    @author Ceki G&uuml;lc&uuml;


    @since 1.2.16 */
 public class EnhancedPatternLayout extends Layout {
   /** Default pattern string for log output. Currently set to the
       string <b>"%m%n"</b> which just prints the application supplied
       message. */
   public static final String DEFAULT_CONVERSION_PATTERN = "%m%n";

   /** A conversion pattern equivalent to the TTCCCLayout.
       Current value is <b>%r [%t] %p %c %x - %m%n</b>. */
   public static final String TTCC_CONVERSION_PATTERN =
     "%r [%t] %p %c %x - %m%n";

     /**
      * Initial size of internal buffer, no longer used.
      * @deprecated since 1.3
      */
   protected final int BUF_SIZE = 256;

     /**
      * Maximum capacity of internal buffer, no longer used.
      * @deprecated since 1.3
      */
   protected final int MAX_CAPACITY = 1024;

   /**
    * Customized pattern conversion rules are stored under this key in the
    * {@link org.apache.log4j.spi.LoggerRepository LoggerRepository} object store.
    */
   public static final String PATTERN_RULE_REGISTRY = "PATTERN_RULE_REGISTRY";


   /**
     *  Initial converter for pattern.
     */
   private PatternConverter head;

   /**
    * Conversion pattern.
    */
   private String conversionPattern;

   /**
    * True if any element in pattern formats information from exceptions.
    */
   private boolean handlesExceptions;

   /**
      Constructs a EnhancedPatternLayout using the DEFAULT_LAYOUT_PATTERN.

      The default pattern just produces the application supplied message.
   */
   public EnhancedPatternLayout() {
     this(DEFAULT_CONVERSION_PATTERN);
   }

   /**
     * Constructs a EnhancedPatternLayout using the supplied conversion pattern.
    * @param pattern conversion pattern.
   */
   public EnhancedPatternLayout(final String pattern) {
     this.conversionPattern = pattern;
     head = createPatternParser(
             (pattern == null) ? DEFAULT_CONVERSION_PATTERN : pattern).parse();
     if (head instanceof BridgePatternConverter) {
         handlesExceptions = !((BridgePatternConverter) head).ignoresThrowable();
     } else {
         handlesExceptions = false;
     }
   }

   /**
    * Set the <b>ConversionPattern</b> option. This is the string which
    * controls formatting and consists of a mix of literal content and
    * conversion specifiers.
    *
    * @param conversionPattern conversion pattern.
   */
   public void setConversionPattern(final String conversionPattern) {
     this.conversionPattern =
       OptionConverter.convertSpecialChars(conversionPattern);
       head = createPatternParser(this.conversionPattern).parse();
       if (head instanceof BridgePatternConverter) {
           handlesExceptions = !((BridgePatternConverter) head).ignoresThrowable();
       } else {
           handlesExceptions = false;
       }
   }

   /**
    *  Returns the value of the <b>ConversionPattern</b> option.
    * @return conversion pattern.
    */
   public String getConversionPattern() {
     return conversionPattern;
   }


     /**
       Returns PatternParser used to parse the conversion string. Subclasses
       may override this to return a subclass of PatternParser which recognize
       custom conversion characters.

       @since 0.9.0
     */
     protected org.apache.log4j.helpers.PatternParser createPatternParser(String pattern) {
       return new org.apache.log4j.pattern.BridgePatternParser(pattern);
     }


   /**
     Activates the conversion pattern. Do not forget to call this method after
     you change the parameters of the EnhancedPatternLayout instance.
   */
   public void activateOptions() {
       // nothing to do.
   }


   /**
    *  Formats a logging event to a writer.
    * @param event logging event to be formatted.
   */
   public String format(final LoggingEvent event) {
       StringBuffer buf = new StringBuffer();
       for(PatternConverter c = head;
           c != null;
           c = c.next) {
           c.format(buf, event);
       }
       return buf.toString();
   }

   /**
    * Will return false if any of the conversion specifiers in the pattern
    * handles {@link Exception Exceptions}.
    * @return true if the pattern formats any information from exceptions.
    */
   public boolean ignoresThrowable() {
     return !handlesExceptions;
   }
 }
	/*
	* 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.helpers.OptionConverter;
	import org.apache.log4j.helpers.PatternConverter;
	import org.apache.log4j.pattern.BridgePatternConverter;
	import org.apache.log4j.spi.LoggingEvent;


	// Contributors: Nelson Minar <nelson@monkey.org>
	// Anders Kristensen <akristensen@dynamicsoft.com>

	/**
	* This class is an enhanced version of org.apache.log4j.PatternLayout
	* which was originally developed as part of the abandoned log4j 1.3
	* effort and has been available in the extras companion.
	* This pattern layout should be used in preference to
	* org.apache.log4j.PatternLayout except when compatibility
	* where PatternLayout has been extended either through subclassing
	* or alternative pattern parsers.
	*
	*
	* <p>A flexible layout configurable with pattern string. The goal of this class
	* is to {@link #format format} a {@link LoggingEvent} and return the results
	* in a {@link StringBuffer}. The format of the result depends on the
	* <em>conversion pattern</em>.
	* <p>
	*
	* <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>Note that you are free to insert any literal text within the
	* conversion pattern.</i>
	* </p>

	<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 EnhancedPatternLayout. 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
	NameAbbreviator pattern.

	<p>For example, for the category name "alpha.beta.gamma" the pattern
	<b>%c{2}</b> will output the last two elements ("beta.gamma"),
	<b>%c{-2}</b> will remove two elements leaving "gamma",
	<b>%c{1.}</b> will output "a.b.gamma".

	</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.

	<td>Used to output the category of the logging event. The
	category conversion specifier can be optionally followed by
	NameAbbreviator pattern.

	<p>For example, for the category name "alpha.beta.gamma" the pattern
	<b>%c{2}</b> will output the last two elements ("beta.gamma"),
	<b>%c{-2}</b> will remove two elements leaving "gamma",
	<b>%c{1.}</b> will output "a.b.gamma".

	<p><b>WARNING</b> Generating the caller class information is
	slow. Thus, its 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 set of braces containing a
	date and time pattern strings {@link java.text.SimpleDateFormat},
	<em>ABSOLUTE</em>, <em>DATE</em> or <em>ISO8601</em>
	and a set of braces containing a time zone id per
	{@link java.util.TimeZone#getTimeZone(String)}.
	For example, <b>%d{HH:mm:ss,SSS}</b>,
	<b>%d{dd MMM yyyy HH:mm:ss,SSS}</b>,
	<b>%d{DATE}</b> or <b>%d{HH:mm:ss}{GMT+0}</b>. If no date format specifier is given then
	ISO8601 format is assumed.
	</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 and 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, its
	generation is <em>extremely</em> slow and 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 and 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 and 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 since 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>


	<tr>
	<td align=center><b>X</b></td>

	<td>

	<p>Used to output the MDC (mapped diagnostic context) associated
	with the thread that generated the logging event. The <b>X</b>
	conversion character can be followed by the key for the
	map placed between braces, as in <b>%X{clientNumber}</b> where
	<code>clientNumber</code> is the key. The value in the MDC
	corresponding to the key will be output. If no additional sub-option
	is specified, then the entire contents of the MDC key value pair set
	is output using a format {{key1,val1},{key2,val2}}</p>

	<p>See {@link MDC} class for more details.
	</p>

	</td>
	</tr>

	<tr>
	<td align=center><b>properties</b></td>

	<td>
	<p>Used to output the Properties associated
	with the logging event. The <b>properties</b>
	conversion word can be followed by the key for the
	map placed between braces, as in <b>%properties{application}</b> where
	<code>application</code> is the key. The value in the Properties bundle
	corresponding to the key will be output. If no additional sub-option
	is specified, then the entire contents of the Properties key value pair set
	is output using a format {{key1,val1},{key2,val2}}</p>
	</td>
	</tr>

	<tr>
	<td align=center><b>throwable</b></td>

	<td>
	<p>Used to output the Throwable trace that has been bound to the LoggingEvent, by
	default this will output the full trace as one would normally
	find by a call to Throwable.printStackTrace().
	<b>%throwable{short}</b> or <b>%throwable{1}</b> will output the first line of
	stack trace. <b>throwable{none}</b> or <b>throwable{0}</b> will suppress
	the stack trace. <b>%throwable{n}</b> will output n lines of stack trace
	if a positive integer or omit the last -n lines if a negative integer.
	If no %throwable pattern is specified, the appender will take
	responsibility to output the stack trace as it sees fit.</p>
	</td>
	</tr>

	<tr>

	<td align=center><b>%</b></td>

	<td>The sequence %% outputs a single percent sign.
	</td>
	</tr>

	</table>

	<p>By default the relevant information is output as is. However,
	with the aid of format modifiers it is possible to change the
	minimum field width, the maximum field width, justification
	and truncation.

	<p>The optional format modifiers are placed between the percent sign
	and the conversion character.

	<p>The <em>left justification flag</em>, the minus sign (-),
	the <em>right truncation flag</em>, the exclamation mark (!),
	or any combination appear first. Followed by the
	optional <em>minimum field width</em> modifier. This is a decimal
	constant that represents the minimum number of characters to
	output. If the data item requires fewer characters, it is padded on
	either the left or the right until the minimum width is
	reached. The default is to pad on the left (right justify) but you
	can specify right padding with the left justification flag. The
	padding character is space. If the data item is larger than the
	minimum field width, the field is expanded to accommodate the
	data. The value is never truncated.

	<p>This behavior can be changed using the <em>maximum field
	width</em> modifier which is designated by a period followed by a
	decimal constant. If the data item is longer than the maximum
	field, then the extra characters are removed from the
	<em>beginning</em> of the data item and not from the end. For
	example, it the maximum field width is eight and the data item is
	ten characters long, then the first two characters of the data item
	are dropped. This behavior deviates from the printf function in C
	where truncation is done from the end. The <em>right truncation flag</em>,
	described previously, will override this behavior.

	<p>Below are various format modifier examples for the category
	conversion specifier.

	<p>
	<TABLE BORDER=1 CELLPADDING=8>
	<th>Format modifier
	<th>left justify
	<th>minimum width
	<th>maximum width
	<th>comment

	<tr>
	<td align=center>%20c</td>
	<td align=center>false</td>
	<td align=center>20</td>
	<td align=center>none</td>

	<td>Left pad with spaces if the category name is less than 20
	characters long.

	<tr> <td align=center>%-20c</td> <td align=center>true</td> <td
	align=center>20</td> <td align=center>none</td> <td>Right pad with
	spaces if the category name is less than 20 characters long.

	<tr>
	<td align=center>%.30c</td>
	<td align=center>NA</td>
	<td align=center>none</td>
	<td align=center>30</td>

	<td>Truncate from the beginning if the category name is longer than 30
	characters.

	<tr>
	<td align=center>%!.30c</td>
	<td align=center>NA</td>
	<td align=center>none</td>
	<td align=center>30</td>

	<td>Truncate from the end if the category name is longer than 30
	characters.

	<tr>
	<td align=center>%20.30c</td>
	<td align=center>false</td>
	<td align=center>20</td>
	<td align=center>30</td>

	<td>Left pad with spaces if the category name is shorter than 20
	characters. However, if category name is longer than 30 characters,
	then truncate from the beginning.

	<tr>
	<td align=center>%-20.30c</td>
	<td align=center>true</td>
	<td align=center>20</td>
	<td align=center>30</td>

	<td>Right pad with spaces if the category name is shorter than 20
	characters. However, if category name is longer than 30 characters,
	then truncate from the beginning.

	</table>

	<p>Below are some examples of conversion patterns.

	<dl>

	<p><dt><b>%r [%t] %-5p %c %x - %m%n</b>
	<p><dd>This is essentially the TTCC layout.

	<p><dt><b>%-6r [%15.15t] %-5p %30.30c %x - %m%n</b>

	<p><dd>Similar to the TTCC layout except that the relative time is
	right padded if less than 6 digits, thread name is right padded if
	less than 15 characters and truncated if longer and the category
	name is left padded if shorter than 30 characters and truncated if
	longer.

	</dl>

	<p>The above text is largely inspired from Peter A. Darnell and
	Philip E. Margolis' highly recommended book "C -- a Software
	Engineering Approach", ISBN 0-387-97389-3.

	@author <a href="mailto:cakalijp@Maritz.com">James P. Cakalic</a>
	@author Ceki Gülcü


	@since 1.2.16 */
	public class EnhancedPatternLayout extends Layout {
	/** Default pattern string for log output. Currently set to the
	string <b>"%m%n"</b> which just prints the application supplied
	message. */
	public static final String DEFAULT_CONVERSION_PATTERN = "%m%n";

	/** A conversion pattern equivalent to the TTCCCLayout.
	Current value is <b>%r [%t] %p %c %x - %m%n</b>. */
	public static final String TTCC_CONVERSION_PATTERN =
	"%r [%t] %p %c %x - %m%n";

	/**
	* Initial size of internal buffer, no longer used.
	* @deprecated since 1.3
	*/
	protected final int BUF_SIZE = 256;

	/**
	* Maximum capacity of internal buffer, no longer used.
	* @deprecated since 1.3
	*/
	protected final int MAX_CAPACITY = 1024;

	/**
	* Customized pattern conversion rules are stored under this key in the
	* {@link org.apache.log4j.spi.LoggerRepository LoggerRepository} object store.
	*/
	public static final String PATTERN_RULE_REGISTRY = "PATTERN_RULE_REGISTRY";


	/**
	* Initial converter for pattern.
	*/
	private PatternConverter head;

	/**
	* Conversion pattern.
	*/
	private String conversionPattern;

	/**
	* True if any element in pattern formats information from exceptions.
	*/
	private boolean handlesExceptions;

	/**
	Constructs a EnhancedPatternLayout using the DEFAULT_LAYOUT_PATTERN.

	The default pattern just produces the application supplied message.
	*/
	public EnhancedPatternLayout() {
	this(DEFAULT_CONVERSION_PATTERN);
	}

	/**
	* Constructs a EnhancedPatternLayout using the supplied conversion pattern.
	* @param pattern conversion pattern.
	*/
	public EnhancedPatternLayout(final String pattern) {
	this.conversionPattern = pattern;
	head = createPatternParser(
	(pattern == null) ? DEFAULT_CONVERSION_PATTERN : pattern).parse();
	if (head instanceof BridgePatternConverter) {
	handlesExceptions = !((BridgePatternConverter) head).ignoresThrowable();
	} else {
	handlesExceptions = false;
	}
	}

	/**
	* Set the <b>ConversionPattern</b> option. This is the string which
	* controls formatting and consists of a mix of literal content and
	* conversion specifiers.
	*
	* @param conversionPattern conversion pattern.
	*/
	public void setConversionPattern(final String conversionPattern) {
	this.conversionPattern =
	OptionConverter.convertSpecialChars(conversionPattern);
	head = createPatternParser(this.conversionPattern).parse();
	if (head instanceof BridgePatternConverter) {
	handlesExceptions = !((BridgePatternConverter) head).ignoresThrowable();
	} else {
	handlesExceptions = false;
	}
	}

	/**
	* Returns the value of the <b>ConversionPattern</b> option.
	* @return conversion pattern.
	*/
	public String getConversionPattern() {
	return conversionPattern;
	}


	/**
	Returns PatternParser used to parse the conversion string. Subclasses
	may override this to return a subclass of PatternParser which recognize
	custom conversion characters.

	@since 0.9.0
	*/
	protected org.apache.log4j.helpers.PatternParser createPatternParser(String pattern) {
	return new org.apache.log4j.pattern.BridgePatternParser(pattern);
	}


	/**
	Activates the conversion pattern. Do not forget to call this method after
	you change the parameters of the EnhancedPatternLayout instance.
	*/
	public void activateOptions() {
	// nothing to do.
	}


	/**
	* Formats a logging event to a writer.
	* @param event logging event to be formatted.
	*/
	public String format(final LoggingEvent event) {
	StringBuffer buf = new StringBuffer();
	for(PatternConverter c = head;
	c != null;
	c = c.next) {
	c.format(buf, event);
	}
	return buf.toString();
	}

	/**
	* Will return false if any of the conversion specifiers in the pattern
	* handles {@link Exception Exceptions}.
	* @return true if the pattern formats any information from exceptions.
	*/
	public boolean ignoresThrowable() {
	return !handlesExceptions;
	}
	}