org.apache.log4j.PatternLayout 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.spi.LoggingEvent;
import org.apache.log4j.helpers.PatternParser;
import org.apache.log4j.helpers.PatternConverter;
// Contributors: Nelson Minar
// Anders Kristensen
/**
*
* A flexible layout configurable with pattern string.
*
* This code is known to have synchronization and other issues which are not
* present in org.apache.log4j.EnhancedPatternLayout. EnhancedPatternLayout
* should be used in preference to PatternLayout. EnhancedPatternLayout is
* distributed in the log4j extras companion.
*
*
* 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 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.
*
*
* 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 PatternLayout. 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 precision specifier, that is
* a decimal constant in brackets.
*
*
* 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.
*
*
* For example, for the category name "a.b.c" the pattern %c{2} will
* output "b.c".
*
*
*
*
*
* 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.
*
*
* 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.
*
*
* For example, for the class name "org.apache.xyz.SomeClass", the pattern
* %C{1} will output "SomeClass".
*
*
* WARNING Generating the caller class information is slow. Thus, 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 date format specifier enclosed
* between braces. For example, %d{HH:mm:ss,SSS} or
* %d{dd MMM yyyy HH:mm:ss,SSS}. If no date format
* specifier is given then ISO8601 format is assumed.
*
*
* 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 SimpleDateFormat is quite poor.
*
*
* 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, %d{ISO8601} or %d{ABSOLUTE}.
*
*
* These dedicated date formatters perform significantly better than
* {@link java.text.SimpleDateFormat}.
*
*
*
* 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 from 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
* must 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.
*
*
*
* See {@link MDC} class for more details.
*
*
*
*
*
*
*
* %
*
* 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 0.8.2
*/
public class PatternLayout extends Layout {
/**
* Default pattern string for log output. Currently set to the string
* "%m%n" which just prints the application supplied message.
*/
public final static String DEFAULT_CONVERSION_PATTERN = "%m%n";
/**
* A conversion pattern equivalent to the TTCCCLayout. Current value is %r
* [%t] %p %c %x - %m%n.
*/
public final static String TTCC_CONVERSION_PATTERN = "%r [%t] %p %c %x - %m%n";
protected final int BUF_SIZE = 256;
protected final int MAX_CAPACITY = 1024;
// output buffer appended to when format() is invoked
private StringBuffer sbuf = new StringBuffer(BUF_SIZE);
private String pattern;
private PatternConverter head;
/**
* 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.
*/
public PatternLayout(String pattern) {
this.pattern = pattern;
head = createPatternParser((pattern == null) ? DEFAULT_CONVERSION_PATTERN : pattern).parse();
}
/**
* Set the ConversionPattern option. This is the string which controls
* formatting and consists of a mix of literal content and conversion
* specifiers.
*/
public void setConversionPattern(String conversionPattern) {
pattern = conversionPattern;
head = createPatternParser(conversionPattern).parse();
}
/**
* Returns the value of the ConversionPattern option.
*/
public String getConversionPattern() {
return pattern;
}
/**
* Does not do anything as options become effective
*/
public void activateOptions() {
// nothing to do.
}
/**
* The PatternLayout does not handle the throwable contained within
* {@link LoggingEvent LoggingEvents}. Thus, it returns true.
*
* @since 0.8.4
*/
public boolean ignoresThrowable() {
return true;
}
/**
* 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 PatternParser createPatternParser(String pattern) {
return new PatternParser(pattern);
}
/**
* Produces a formatted string as specified by the conversion pattern.
*/
public String format(LoggingEvent event) {
// Reset working stringbuffer
if (sbuf.capacity() > MAX_CAPACITY) {
sbuf = new StringBuffer(BUF_SIZE);
} else {
sbuf.setLength(0);
}
PatternConverter c = head;
while (c != null) {
c.format(sbuf, event);
c = c.next;
}
return sbuf.toString();
}
}