Configuring logging in Spring

If you’re like me, then you probably don’t want thousands of configuration files for your applications and keep everything in one place.
Few years back I was using Log4J for logging, but as a new solution has made its way into the SDK, I changed too. I know that a lot of people will argue and say that Log4J is much better, but I like more to use standard solution. Also Log4J became more like a de facto industry standard, so it becomes more like of a personal preference.
Anyway the solution proposed onward can be applied to both java.util.logging and Log4J, but I will exemplify only the first.
With Spring IoC container, you can easily create beans in your context. The idea is very simple, just create a bean using the Spring IoC and use the setter methods to configure the logging system.

public class LogConfigurator {

  public void setLogLevels(Map<String, String> logLevels) {
    for (String loggerName : logLevels.keySet()) {
      Logger.getLogger(loggerName).setLevel(Level.parse(logLevels.get(loggerName)));
    }
  }

  public void setLogHandlers(Map<String, Handler> logHandlers) {
    for (String loggerName : logHandlers.keySet()) {
      Logger.getLogger(loggerName).addHandler(logHandlers.get(loggerName));
    }
  }

  public void setLogUseParentHandlers(Map<String, Boolean> logUseParentHandlers) {
    for (String loggerName : logUseParentHandlers.keySet()) {
      Logger.getLogger(loggerName).setUseParentHandlers(logUseParentHandlers.get(loggerName));
    }        
  }
}

The above methods are used to set the logging levels, handlers and if to use the parent logger handlers. They receive as parameter a map between the logger name and the setting.

Now in your applicationContext.xml file you will have:

<bean id="logConfigurator" class="LogConfigurator">
  <property name="logHandlers">
    <map>
      <entry key="module.1" value-ref="customHandler"/>
    </map>
  </property>
  <property name="logLevels">
    <map>
      <entry key="module.2" value="INFO"/>
    </map>
  </property>
</bean>

This will set the log level of the second module to INFO and will add a custom handler to the first module.

You can apply the same technique to some other configurations as well.

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