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Logging guidelines » History » Revision 3

Revision 2 (Tobias Wich, 07/25/2012 11:31 AM) → Revision 3/4 (Tobias Wich, 09/14/2012 04:17 PM)

h1. Logging guidelines 

 {{toc}} 

 h2. Framework 

 h3. SLF4J (Simple Logging Facade for Java) 

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

 h3. Maven 

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

 h3. Preamble 

 <pre> 
 import org.slf4j.Logger; 
 import org.slf4j.LoggerFactory; 

 private static final Logger logger = LoggerFactory.getLogger(MYCLASS.class); 
 </pre> 

 h3. SLF4J with java.util.logging backend 

 *TODO:* rewrite for logback-classic 

 This code SHOULD only be using in TestNG. 

 <pre> 
 // Reset configuration to avoid multiple log entries. 
 java.util.logging.LogManager.getLogManager().reset(); 
 // Add new console handler 
 ConsoleHandler ch = new ConsoleHandler(); 
 ch.setLevel(Level.ALL); 
 // Set logging level 
 LogManager.getLogger(MYCLASS.class.getName()).setLevel(Level.FINE); 

 // Log message as jdk logging level INFO 
 logger.info("Log my message: {}", message); 
 // Log message as jdk logging level FINE 
 logger.debug("Log my message: {}", message); 
 // Log message as jdk logging level WARNING 
 logger.warn("Log my message: {}", message); 
 // Log message as jdk logging level SEVERE 
 logger.error("Log my message: {}", message); 
 </pre> 



 h2. Levels 

 h3. Exceptions 

 <pre> 
 import org.slf4j.Logger; 
 import org.slf4j.LoggerFactory; 

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

 try{ 
  ... 
 } catch (Exception e){ 
   logger.error(ex.getMessage(), ex); 
 } 
 </pre> 
 Or set a descriptive message: 
 <pre> 
 try{ 
  ... 
 } catch (Exception e){ 
   logger.error("Error while reading value X.", ex); 
 } 
 </pre> 


 h3. Messages 

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

 <pre> 
 import org.slf4j.Logger; 
 import org.slf4j.LoggerFactory; 

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

 logger.debug("Message received:\n{}", message); 
 logger.debug("Message sent:\n{}", message); 
 </pre> 

 h3. Events 

 E.g. GUI events. 

 <pre> 
 import org.slf4j.Logger; 
 import org.slf4j.LoggerFactory; 

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

 logger.debug("Event: {}", event); 
 </pre> 

 h2. Notes 

 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. 

 <pre> 
 public void foo(Bar b) { 
     logger.trace("Enter function foo: {}", b); 
     ... 
 </pre>