The version of Apache log4j used by SoundHelix.

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v1.3alpha8 :: src / java / org / apache / log4j /

PatternLayout.java

/*
 * Copyright 1999,2005 The Apache Software Foundation.
 *
 * Licensed 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.pattern.FormattingInfo;
import org.apache.log4j.pattern.LiteralPatternConverter;
import org.apache.log4j.pattern.LoggingEventPatternConverter;
import org.apache.log4j.pattern.PatternParser;
import org.apache.log4j.spi.LoggingEvent;
import org.apache.log4j.spi.LoggerRepositoryEx;


import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;


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

/**
  * <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 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 set of braces containing a
         date and time pattern strings {@link java.text.SimpleDateFormat},
         <em>ABSOLUTE</em>, <em>DATE</em> or <em>ISO8601</em>.
         For example, <b>%d{HH:mm:ss,SSS}</b>,
         <b>%d{dd&nbsp;MMM&nbsp;yyyy&nbsp;HH:mm:ss,SSS}</b> or
         <b>%d{DATE}</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. Its 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 since the start
     of the application 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().
     The throwable conversion word can be followed by an option in the form <b>%throwable{short}</b>
     which will only output the first line of the ThrowableInformation.</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 and justification.

   <p>The optional format modifier is placed between the percent sign
   and the conversion character.

   <p>The first optional format modifier is the <em>left justification
   flag</em> which is just the minus (-) character. Then comes 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.

   <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>%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 0.8.2 */
public class PatternLayout 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";

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

  /**
   * Pattern converters.
   */
  private LoggingEventPatternConverter[] patternConverters;

  /**
   * Field widths and alignment corresponding to pattern converters.
   */
  private FormattingInfo[] patternFields;

  /**
   * String buffer used in formatting.
   */
  private StringBuffer buf = new StringBuffer();

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

  /**
     Constructs a PatternLayout using the DEFAULT_LAYOUT_PATTERN.

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

  /**
    * Constructs a PatternLayout using the supplied conversion pattern.
   * @param pattern conversion pattern.
  */
  public PatternLayout(String pattern) {
    this.conversionPattern = pattern;
    activateOptions();
  }

  /**
   * 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(String conversionPattern) {
    this.conversionPattern =
      OptionConverter.convertSpecialChars(conversionPattern);
  }

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

  /**
    Activates the conversion pattern. Do not forget to call this method after
    you change the parameters of the PatternLayout instance.
  */
  public void activateOptions() {
    List converters = new ArrayList();
    List fields = new ArrayList();
    Map converterRegistry = null;

    if (this.repository != null) {
      if (repository instanceof LoggerRepositoryEx) {
        converterRegistry =
            (Map) ((LoggerRepositoryEx) repository).getObject(PATTERN_RULE_REGISTRY);
      }
    }

    PatternParser.parse(
      conversionPattern, converters, fields, converterRegistry,
      PatternParser.getPatternLayoutRules(), getLogger());

    patternConverters = new LoggingEventPatternConverter[converters.size()];
    patternFields = new FormattingInfo[converters.size()];

    int i = 0;
    Iterator converterIter = converters.iterator();
    Iterator fieldIter = fields.iterator();

    while (converterIter.hasNext()) {
      Object converter = converterIter.next();

      if (converter instanceof LoggingEventPatternConverter) {
        patternConverters[i] = (LoggingEventPatternConverter) converter;
        handlesExceptions |= patternConverters[i].handlesThrowable();
      } else {
        patternConverters[i] = new LiteralPatternConverter("");
      }

      if (fieldIter.hasNext()) {
        patternFields[i] = (FormattingInfo) fieldIter.next();
      } else {
        patternFields[i] = FormattingInfo.getDefault();
      }

      i++;
    }
  }

  /**
   *  Formats a logging event to a writer.
   * @param event logging event to be formatted.
  */
  public String format(final LoggingEvent event) {
    buf.setLength(0);

    for (int i = 0; i < patternConverters.length; i++) {
      int startField = buf.length();
      patternConverters[i].format(event, buf);
      patternFields[i].format(startField, buf);
    }

    String retval = buf.toString();
    buf.setLength(0);
    return retval;
  }

  /**
   * 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;
  }
}
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