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

[QOS.CH (JIRA)]

Joern Huxhorn created SLF4J-396:
-----------------------------------

             Summary: 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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