org.apache.log4j.EnhancedPatternLayout Maven / Gradle / Ivy
/*
* 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
// Anders Kristensen
/**
* 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.
*
*
* 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
* conversion pattern.
*
*
*
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
* conversion specifiers.
*
*
Note that you are free to insert any literal text within the
* conversion pattern.
*
Each conversion specifier starts with a percent sign (%) and is
followed by optional format modifiers and a conversion
character. 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.
Let the conversion pattern be "%-5p [%t]: %m%n" and assume
that the log4j environment was set to use a EnhancedPatternLayout. Then the
statements
Category root = Category.getRoot();
root.debug("Message 1");
root.warn("Message 2");
would yield the output
DEBUG [main]: Message 1
WARN [main]: Message 2
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
%-5p means the priority of the logging event should be left
justified to a width of five characters.
The recognized conversion characters are
Conversion Character
Effect
c
Used to output the category of the logging event. The
category conversion specifier can be optionally followed by
NameAbbreviator pattern.
For example, for the category name "alpha.beta.gamma" the pattern
%c{2} will output the last two elements ("beta.gamma"),
%c{-2} will remove two elements leaving "gamma",
%c{1.} will output "a.b.gamma".
C
Used to output the fully qualified class name of the caller
issuing the logging request. This conversion specifier
can be optionally followed by precision specifier, that
is a decimal constant in brackets.
Used to output the category of the logging event. The
category conversion specifier can be optionally followed by
NameAbbreviator pattern.
For example, for the category name "alpha.beta.gamma" the pattern
%c{2} will output the last two elements ("beta.gamma"),
%c{-2} will remove two elements leaving "gamma",
%c{1.} will output "a.b.gamma".
WARNING Generating the caller class information is
slow. Thus, its use should be avoided unless execution speed is
not an issue.
d 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},
ABSOLUTE, DATE or ISO8601
and a set of braces containing a time zone id per
{@link java.util.TimeZone#getTimeZone(String)}.
For example, %d{HH:mm:ss,SSS},
%d{dd MMM yyyy HH:mm:ss,SSS},
%d{DATE} or %d{HH:mm:ss}{GMT+0}. If no date format specifier is given then
ISO8601 format is assumed.
F
Used to output the file name where the logging request was
issued.
WARNING Generating caller location information is
extremely slow and should be avoided unless execution speed
is not an issue.
l
Used to output location information of the caller which generated
the logging event.
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.
The location information can be very useful. However, its
generation is extremely slow and should be avoided
unless execution speed is not an issue.
L
Used to output the line number from where the logging request
was issued.
WARNING Generating caller location information is
extremely slow and should be avoided unless execution speed
is not an issue.
m
Used to output the application supplied message associated with
the logging event.
M
Used to output the method name where the logging request was
issued.
WARNING Generating caller location information is
extremely slow and should be avoided unless execution speed
is not an issue.
n
Outputs the platform dependent line separator character or
characters.
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.
p
Used to output the priority of the logging event.
r
Used to output the number of milliseconds elapsed since the construction
of the layout until the creation of the logging event.
t
Used to output the name of the thread that generated the
logging event.
x
Used to output the NDC (nested diagnostic context) associated
with the thread that generated the logging event.
X
Used to output the MDC (mapped diagnostic context) associated
with the thread that generated the logging event. The X
conversion character can be followed by the key for the
map placed between braces, as in %X{clientNumber} where
clientNumber 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}}
See {@link MDC} class for more details.
properties
Used to output the Properties associated
with the logging event. The properties
conversion word can be followed by the key for the
map placed between braces, as in %properties{application} where
application 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}}
throwable
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().
%throwable{short} or %throwable{1} will output the first line of
stack trace. throwable{none} or throwable{0} will suppress
the stack trace. %throwable{n} 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.
%
The sequence %% outputs a single percent sign.
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.
The optional format modifier is placed between the percent sign
and the conversion character.
The first optional format modifier is the left justification
flag which is just the minus (-) character. Then comes the
optional minimum field width 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.
This behavior can be changed using the maximum field
width 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
beginning 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.
Below are various format modifier examples for the category
conversion specifier.
Format modifier
left justify
minimum width
maximum width
comment
%20c
false
20
none
Left pad with spaces if the category name is less than 20
characters long.
%-20c true 20 none Right pad with
spaces if the category name is less than 20 characters long.
%.30c
NA
none
30
Truncate from the beginning if the category name is longer than 30
characters.
%20.30c
false
20
30
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.
%-20.30c
true
20
30
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.
Below are some examples of conversion patterns.
- %r [%t] %-5p %c %x - %m%n
- This is essentially the TTCC layout.
- %-6r [%15.15t] %-5p %30.30c %x - %m%n
- 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.
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 James P. Cakalic
@author Ceki Gülcü
@since 1.2.16 */
public class EnhancedPatternLayout extends Layout {
/** Default pattern string for log output. Currently set to the
string "%m%n" 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 %r [%t] %p %c %x - %m%n. */
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 ConversionPattern 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 ConversionPattern 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;
}
}