Logger Modification

Already exisiting loggers can be modified by Log4E.

Note that the modification algorithm changed from v0.5.5 to the current version and that using this task could delete a logger message under certain circumstances! See the modification algorithm section for more information.

Several operation are executed:

Example:

Before:

public class ActualClass {
	//typical copy/paste mistake
	/**
	 * Logger for this class
	 */
	private static final Logger logger = Logger.getLogger(Other.class);
	
	public String myMethod(String str, int integer) {
		logger.debug("otherMethod() - starttext");
		try {
			
		} catch (Exception e) {
			logger.error("otherMethod() - errortext", e);
			
			//Your code...
			
			logger.debug("otherMethod() - othertext");
			
			logger.debug("otherMethod() - returntext");
			return "text";
		}
		logger.debug("otherMethod() - endtext");
		return toString();
	}
}

After:

public class ActualClass {
	//typical copy/paste mistake
	/**
	 * Logger for this class
	 */
	private static final Logger logger = Logger.getLogger(ActualClass.class);
	
	public String myMethod(String str, int integer) {
		if (logger.isDebugEnabled()) {
			logger.debug(
				"myMethod(String str = "
					+ str
					+ ", int integer = "
					+ integer
					+ ") - starttext");
		}
		try {
			
		} catch (Exception e) {
			logger.error("myMethod() - errortext", e);
			
			//Your code...
			
			if (logger.isDebugEnabled()) {
				logger.debug("myMethod() - othertext");
			}
			
			if (logger.isDebugEnabled()) {
				logger.debug("myMethod() - returntext - return value = text");
			}
			return "text";
		}
	
		String returnString = toString();
		if (logger.isDebugEnabled()) {
			logger.debug("myMethod() - endtext - return value = " + returnString);
		}
		return returnString;
	}
}

Note that Log4E checks if "returnString" already exists and appends a number. e.g. if "returnString" exists the new variable would be "returnString2" (and so on).

Modification Algorithm

To analyse the existing log statement in source code, Log4E uses the accordingly template (defined in "Log4E > Profile > Templates" preference page)

Example 1:

Assume the existing log statement is:

debug("otherMethod() - starttext");

Therefore the accordingly template is:

debug("${enclosing_method}${delimiter}${message}${delimiter}${return_value}")

Log4E makes a guess to map the tokens to the right variables. In this case, assuming that ${delimiter}=" - ", everything is alright. The mapping would be:

${enclosing_method}="otherMethod()"
${message}="starttext"
${return_value}=""

Only the ${message} is kept. Everything else will be replaced with the computed values. The result would be:

debug("myMethod() - starttext");

To compute the right tokens Log4E uses the delimiter. If the delimiter, defined in the "Log4E > Format" preferences, is different to delimiter used in the source code, Log4E won't be able to extract the user message.

Example 2:

Assume the existing log statement is:

debug("otherMethod() : starttext");

Therefore the accordingly template is:

debug("${enclosing_method}${delimiter}${message}${delimiter}${return_value}")

In this case, assuming that ${delimiter}=" - ", the mapping would be:

${enclosing_method}="otherMethod() : starttext"
${message}=""
${return_value}=""

When Log4E recognizes that the ${message} is empty it will pop up a warning. The user can choose from there if he or she wants to start the Preview Wizard before confirming the changes.

If confirmed by user the result would be:

debug("myMethod()");

Note that the logger statement "error("otherMethod()", e)" generated by Log4E doesn't have a message by default. Therefore Log4E will pop up a warning when performing modification even if the message must be empty in this case.

Example 3:

Assume the existing log statement is:

debug("starttext - otherMethod()");

Therefore the accordingly template is:

debug("${enclosing_method}${delimiter}${message}${delimiter}${return_value}")

In this case, assuming that ${delimiter}=" - ", the mapping would be:

${enclosing_method}="starttext"
${message}="otherMethod()"
${return_value}=""

This is the worst case. Log4E does not recognize that the mapping is wrong because ${message} is not empty. Log4E would delete the exisitng message without a warning:

debug("myMethod() - otherMethod()");

Abstract:

The modification task is best used with Log4E generated log statements!

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