[slf4j-dev] [JIRA] (SLF4J-396) Support jul sourceClassName and sourceMethodName in slf4j-bridge.

[QOS.CH (JIRA)]

    [ https://jira.qos.ch/browse/SLF4J-396?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18365#comment-18365 ] 

Joern Huxhorn commented on SLF4J-396:
-------------------------------------

A bit of extra context:

I had my own bridge implementation in Lilith that was predating this one. Yours is the better implementation because it handles the resource bundles appropriately so I decided to drop my own implementation altogether in favor of the {{SLF4JBridgeHandler}}/{{LevelChangePropagator}} combination.

The only downside is the lack of the info mentioned above which my implementation was previously already putting into the {{MDC}}.

> Support jul sourceClassName and sourceMethodName in slf4j-bridge.
> -----------------------------------------------------------------
>
>                 Key: SLF4J-396
>                 URL: https://jira.qos.ch/browse/SLF4J-396
>             Project: SLF4J
>          Issue Type: Improvement
>          Components: jul-to-slf4j
>    Affects Versions: 1.7.24
>         Environment: any
>            Reporter: Joern Huxhorn
>            Assignee: SLF4J developers list
>
> The {{SLF4JBridgeHandler}} is currently dropping some log record info while bridging to slf4j.
> The reason for this is that {{java.util.logging}} logger names are different beasts than slf4j ones. While it is a very common convention that an slf4j logger name equals the class name it's responsible for, this isn't necessarily the case for {{java.util.logging}}.
> That's why {{LogRecord}} contains {{sourceClassName}} and {{sourceMethodName}} fields that are populated by {{Logger.entering}}, {{Logger.exiting}}, {{Logger.throwing}} and the general {{logp/logrb}} methods.
> That info is crucial to the point where the log records are relatively useless without it.
> Example:
> {{Logger.entering("SourceClass","sourceMethod")}} will result in an event that simply says {{ENTRY}}.
> Furthermore, {{jul}} allows for custom {{Level}} instances with a name and an arbitrary {{intValue()}}. While losing those is way less critical since they are already mapped to slf4j levels in a reasonable way, I think it would still be worthwhile to keep that info around.
> I'd suggest to add the following to {{SLF4JBridgeHandler}}:
> {code:java}
> private static final String LEVEL_MDC_KEY = "JUL-Level";
> private static final String LEVEL_VALUE_MDC_KEY = "JUL-Level-Value";
> private static final String SOURCE_CLASS_NAME_MDC_KEY = "JUL-SourceClassName";
> private static final String SOURCE_METHOD_NAME_MDC_KEY = "JUL-SourceMethodName";
> private static void initMDC(LogRecord record) {
>     Level julLevel = record.getLevel();
>     MDC.put(LEVEL_MDC_KEY, julLevel.getName());
>     MDC.put(LEVEL_VALUE_MDC_KEY, Integer.toString(julLevel.intValue()));
>     String sourceClassName = record.getSourceClassName();
>     if(sourceClassName != null) {
>         MDC.put(SOURCE_CLASS_NAME_MDC_KEY, sourceClassName);
>     }
>     String sourceMethodName = record.getSourceMethodName();
>     if(sourceMethodName != null) {
>         MDC.put(SOURCE_METHOD_NAME_MDC_KEY, sourceMethodName);
>     }
> }
> private static void clearMDC() {
>     MDC.remove(LEVEL_MDC_KEY);
>     MDC.remove(LEVEL_VALUE_MDC_KEY);
>     MDC.remove(SOURCE_CLASS_NAME_MDC_KEY);
>     MDC.remove(SOURCE_METHOD_NAME_MDC_KEY);
> }
> {code}
> Those methods would then be used in {{publish(LogRecord record)}}:
> {code:java}
> initMDC(record);
> try {
>     if (slf4jLogger instanceof LocationAwareLogger) {
>         callLocationAwareLogger((LocationAwareLogger) slf4jLogger, record);
>     } else {
>         callPlainSLF4JLogger(slf4jLogger, record);
>     }
> }
> finally {
>     clearMDC();
> }
> {code}



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