You can set logger level for class or group of classes by setting next property:
<property name="log4j.category.{component or class name}" value="DEBUG"/>
For example:
We want to log all debug messages for class
org.exoplatform.services.jcr.impl.core.SessionDataManager,
that lies in exo.jcr.component.core
component
<property name="log4j.category.exo.jcr.component.core.SessionDataManager" value="DEBUG"/>
Or we want to log all debug messages for all classes in exo.jcr.component.core component
<property name="log4j.category.exo.jcr.component.core" value="DEBUG"/>
Or we want to log all messages for all kernel components
<property name="log4j.category.exo.kernel" value="DEBUG"/>