Простой калькулятор на Spring MVC MultiActionController

/* Created on Dec 24, 2005 Marina*/
 
package controller;
import java.util.HashMap;
import java.util.Map;
 
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.web.bind.RequestUtils;
import org.springframework.web.servlet.ModelAndView;
 
 
import org.springframework.web.servlet.mvc.multiaction.MultiActionController;
import javax.servlet.http.HttpServletRequest;
 
 
import commands.OperationCommand;
import servises.CalculatorService;
 
public class CalculatorFormController extends MultiActionController {
    
    private CalculatorService calculator = new CalculatorService();
 
    protected final Log logger = LogFactory.getLog(getClass());
    
    public CalculatorFormController(){
        
    }
 
    protected ModelAndView addition(HttpServletRequest request, Object command) throws Exception{
 
        logger.info("[CalculatorFormController] Addition Entering...");
        Map model = new HashMap();
        
        try {           
            OperationCommand operation = (OperationCommand) command;    
            
            String action = RequestUtils.getRequiredStringParameter(request,"action");
            operation.setAction(action);
            if (operation!=null){   
                
                model = getCalculations(operation);             
            }
        }
        catch (Exception e){            
            logger.info("[CalculatorFormController] Exception occured... " + e.getMessage());
        }
        
        return new ModelAndView("result","model", model);
        
    }
 
    protected ModelAndView subtraction (HttpServletRequest request, Object command) throws Exception{
 
        logger.info("[CalculatorFormController] Entering...");
        Map model = new HashMap();
        
        try {           
            OperationCommand operation = (OperationCommand) command;    
            String action = RequestUtils.getRequiredStringParameter(request,"action");
            operation.setAction(action);
            if (operation!=null){               
                model = getCalculations(operation);                     }
        }
        catch (Exception e){            
            logger.info("[CalculatorFormController] Exception occured... " + e.getMessage());
        }
        
        return new ModelAndView("result","model", model);
        
    }
    
    private Map getCalculations(OperationCommand operation){
        String result;
        Map model = new HashMap();
            if((operation.getFirstOperand()==null||operation.getFirstOperand().length()==0))
        {
            operation.setFirstOperand("0");
        }
        else if(operation.getSecondOperand()==null||operation.getSecondOperand().length()==0){
            
            operation.setSecondOperand("0");
        }
            result = calculator.calculate(operation);           
        
        model.put("operation",operation.getAction());
        model.put("result",result);     
        return model;       
    }
    
    public CalculatorService getCalculatorService(){
        return calculator;
    }
}