Bug 165188 logging per report
Setting up a dedicated (birt) report server, which serves all our web apps, leads to a logging desaster. Birtegine logs all messages to one file. There's no info which rptdesign caused the logmessage or who (e.g. user) caused the logmessage. Retrieving who/which rpt caused some logmessage is not possible! There are two possible solutions: (a) prefixing each logmessage with a userdefineable message (task.setLogprefix("myprefix")) (b) set an outputstream for each task (task.setLoggingOutputStream(outputstream)) to split the huge logfile to many small pieces.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/impl/EngineTask.java
log.log( Level.SEVERE, "Parameter {0} doesn't allow a null value.",  
					paramName );
			return false;
		}
		String source = paramHandle.getValidate( );
		if ( source != null && source.length( ) != 0 )
		{
			Object result = executionContext.evaluate( source );
			if ( !( result instanceof Boolean )
					|| !( (Boolean) result ).booleanValue( ) )
			{
				log.log( Level.SEVERE, "Parameter validate failed: ",  
					source );
				return false;
			}
		}
		
		/*
		 * Validate based on parameter type
		 */
		if ( DesignChoiceConstants.PARAM_TYPE_DECIMAL.equals( type )
				|| DesignChoiceConstants.PARAM_TYPE_FLOAT.equals( type ) )
		{
			if ( paramValue instanceof Number )
				return true;
			log
					.log(
							Level.SEVERE,
							"The supplied value {0} for parameter {1} is not a number.", new String[]{paramValue.toString( ), paramName} ); 
			return false;