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Logging guidelines » History » Version 2

Tobias Wich, 07/25/2012 11:31 AM

1 1 Moritz Horsch 
h1. Logging guidelines
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{{toc}}





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h2. Framework





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h3. SLF4J (Simple Logging Facade for Java)





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"Documentation":http://www.slf4j.org/docs.html





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h3. Maven





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No dependency SHOULD be added to the module POM. The slf4j dependency is already defined in the ecard client root POM.





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slf4j needs a backend implementation. For the tests, logback-classic is pulled in by the root POM. For production use, the client artifact must pull in a compile dependency on a backend and configure it appropriately.





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h3. Preamble





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<pre>





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import org.slf4j.Logger;





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import org.slf4j.LoggerFactory;





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private static final Logger logger = LoggerFactory.getLogger(MYCLASS.class);





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</pre>





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h3. SLF4J with java.util.logging backend





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*TODO:* rewrite for logback-classic





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This code SHOULD only be using in TestNG.





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<pre>





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// Reset configuration to avoid multiple log entries.





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java.util.logging.LogManager.getLogManager().reset();





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// Add new console handler





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ConsoleHandler ch = new ConsoleHandler();





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ch.setLevel(Level.ALL);





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// Set logging level





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LogManager.getLogger(MYCLASS.class.getName()).setLevel(Level.FINE);





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// Log message as jdk logging level INFO





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logger.info("Log my message: {}", message);





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// Log message as jdk logging level FINE





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logger.debug("Log my message: {}", message);





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// Log message as jdk logging level WARNING





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logger.warn("Log my message: {}", message);





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// Log message as jdk logging level SEVERE





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logger.error("Log my message: {}", message);





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</pre>





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h2. Levels





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h3. Exceptions





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<pre>





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import org.slf4j.Logger;





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import org.slf4j.LoggerFactory;





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private static final Logger logger = LoggerFactory.getLogger(MYCLASS.class);





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try{





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 ...





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} catch (Exception e){





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  logger.error(ex.getMessage(), ex);





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}





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</pre>





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Or set a descriptive message:





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<pre>





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try{





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 ...





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} catch (Exception e){





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  logger.error("Error while reading value X.", ex);





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}





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</pre>





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h3. Messages





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Messages including  APDUs, eCard-API messages, PAOS messages.





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<pre>





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import org.slf4j.Logger;





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import org.slf4j.LoggerFactory;





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private static final Logger logger = LoggerFactory.getLogger(MYCLASS.class);





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logger.debug("Message received:\n{}", message);





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logger.debug("Message sent:\n{}", message);





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</pre>





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h3. Events





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E.g. GUI events.





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<pre>





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import org.slf4j.Logger;





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import org.slf4j.LoggerFactory;





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private static final Logger logger = LoggerFactory.getLogger(MYCLASS.class);





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logger.debug("Event: {}", event);





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</pre>





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h2. Notes





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h3. Trace statements as the following example shows are omitted, because there is a "slf4j agent":http://www.slf4j.org/extensions.html#javaagent which can automate this task.





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<pre>





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public void foo(Bar b) {





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    logger.trace("Enter function foo: {}", b);





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    ...





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</pre>