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:
其中可能需要转换的地方主要有两块：
- %l
- %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. |