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 dependencies are already defined in the ecard client POM.

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

This code SHOULD only be using in JUnit tests.

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



h2. Levels

h3. Overview
 
Marker are specified in @org.openecard.client.common.logging.LoggingConstants@

* THROWING: [[Logging guidelines#Exceptions|Exceptions]]
* SEVERE:
* INFO:
* CONFIG:
* FINE: [[Logging guidelines#Exceptions|Messages]]
* FINER: [[Logging guidelines#Exceptions|Events]]
* FINEST:

h3. Exceptions

<pre>
import org.openecard.client.common.logging.LoggingConstants;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

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

try{
 ...
} catch (Exception e){
  // <editor-fold defaultstate="collapsed" desc="log exception">
  logger.error(LoggingConstants.THROWING, "Exception", e);
  // </editor-fold>
}
</pre>

h3. Messages

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

<pre>
import org.openecard.client.common.logging.LoggingConstants;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

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

// <editor-fold defaultstate="collapsed" desc="log message">
logger.debug(LoggingConstants.FINE, "Message received:\n{}", message);
// </editor-fold>

// <editor-fold defaultstate="collapsed" desc="log message">
logger.debug(LoggingConstants.FINE, "Message sent:\n{}", message);
// </editor-fold>
</pre>

h3. Events

E.g. GUI events.

<pre>
import org.openecard.client.common.logging.LoggingConstants;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

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

// <editor-fold defaultstate="collapsed" desc="log event">
logger.debug(LoggingConstants.FINER, "Event: {}", event);
// </editor-fold>
</pre>

h2. Notes

h3. Trace statements are omitted

<pre>
logger.trace("Trace a message: {}", message);
</pre>

Will be replaced by "slf4j extension":http://www.slf4j.org/extensions.html#javaagent.

h2. Examples

h3. APDU logging

<pre>
import org.openecard.client.common.ECardConstants;
import org.openecard.client.common.logging.LogManager;

java.util.logging.LogManager.getLogManager().reset();
ConsoleHandler ch = new ConsoleHandler();
ch.setLevel(Level.ALL);
LogManager.getLogger("org.openecard.client.ifd.scio.wrapper").addHandler(ch);
LogManager.getLogger("org.openecard.client.ifd.scio.wrapper").setLevel(Level.FINE);
</pre>