Log4j 与 Logback的ConversionPattern对比

为了能将log4j的配置无缝转到logback，需要了解其中ConversionPattern的差异，以下是对比表格，内容来自:

1. log4j官网
2. logback官网

其中可能需要转换的地方主要有两块：

1. %l
2. %x

Log4j	Log4j Description	Logback	Logback Description
c	Used to output the category of the logging event.	c{length} / lo{length} / logger{length}	Outputs the name of the logger at the origin of the logging event.
C	Used to output the fully qualified class name of the caller issuing the logging request	C{length} class{length}	Outputs the fully-qualified class name of the caller issuing the logging request.
d	Used to output the date of the logging event.	d{pattern} / date{pattern} / d{pattern, timezone} / date{pattern, timezone}	Used to output the date of the logging event.
F	Used to output the file name where the logging request was issued.	F / file	Outputs the file name of the Java source file where the logging request was issued.
l	Used to output location information of the caller which generated the logging event.	caller{depth} / caller{depth, evaluator-1, ... evaluator-n}	Outputs location information of the caller which generated the logging event.
L	Used to output the line number from where the logging request was issued.	L / line	Outputs the line number from where the logging request was issued.
m	Used to output the application supplied message associated with the logging event.	m / msg / message	Outputs the application-supplied message associated with the logging event.
M	Used to output the method name where the logging request was issued.	M / method	Outputs the method name where the logging request was issued.
n	Outputs the platform dependent line separator character or characters.	n	Outputs the platform dependent line separator character or characters.
p	Used to output the priority of the logging event.	p / le / level	Outputs the level 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.	r / relative	Outputs the number of milliseconds elapsed since the start of the application until the creation of the logging event.
t	Used to output the name of the thread that generated the logging event.	t / thread	Outputs 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.	X{key:-defaultVal} / mdc{key:-defaultVal}	Outputs the MDC (mapped diagnostic context) associated with the thread that generated the logging event.
%	The sequence %% outputs a single percent sign.