eventhandlerutil.java

velocity官方工具包 包括各种JAR包 示例 文档等

        {
            EventHandlerMethodExecutor methodExecutor = 
                new IncludeEventHandler.IncludeEventExecutor(
                        context, includeResourcePath, 
                        currentResourcePath, directiveName);
            
            callEventHandlers(
                    applicationEventHandlerIterator, 
                    contextEventHandlerIterator, methodExecutor);
            
            return (String) methodExecutor.getReturnValue();
        }
        catch (RuntimeException e)
        {
            throw e;
        }
        catch (Exception e)
        {
            throw ExceptionUtils.createRuntimeException("Exception in event handler.",e);
        }
    }
   

    /**
     * Called when an invalid get method is encountered.
     * 
     * @param rsvc current instance of RuntimeServices
     * @param context the context when the reference was found invalid
     * @param reference complete invalid reference
     * @param object object from reference, or null if not available
     * @param property name of property, or null if not relevant
     * @param info contains info on template, line, col
     * @return substitute return value for missing reference, or null if no substitute
     */
    public static Object invalidGetMethod(RuntimeServices rsvc,
            InternalContextAdapter context, String reference, 
            Object object, String property, Info info)
    {
        return  
        invalidReferenceHandlerCall (
                new InvalidReferenceEventHandler.InvalidGetMethodExecutor
                (context, reference, object, property, info),
                rsvc, 
                context);       
    }
        
        
   /**
     * Called when an invalid set method is encountered.
     * 
     * @param rsvc current instance of RuntimeServices
     * @param context the context when the reference was found invalid
     * @param leftreference left reference being assigned to
     * @param rightreference invalid reference on the right
     * @param info contains info on template, line, col
     */
    public static void invalidSetMethod(RuntimeServices rsvc,
            InternalContextAdapter context, String leftreference, 
            String rightreference, Info info)
    {
        /**
         * ignore return value
         */
        invalidReferenceHandlerCall (
                new InvalidReferenceEventHandler.InvalidSetMethodExecutor
                (context, leftreference, rightreference, info),
                rsvc, 
                context);   
    }
    
    /**
     * Called when an invalid method is encountered.
     * 
     * @param rsvc current instance of RuntimeServices
     * @param context the context when the reference was found invalid
     * @param reference complete invalid reference
     * @param object object from reference, or null if not available
     * @param method name of method, or null if not relevant
     * @param info contains info on template, line, col
     * @return substitute return value for missing reference, or null if no substitute
     */
    public static Object invalidMethod(RuntimeServices rsvc,
            InternalContextAdapter context,  String reference,
            Object object, String method, Info info)
    {
        return 
        invalidReferenceHandlerCall (
                new InvalidReferenceEventHandler.InvalidMethodExecutor
                (context, reference, object, method, info),
                rsvc, 
                context);       
    }
    
    
    /**
     * Calls event handler method with appropriate chaining across event handlers.
     * 
     * @param methodExecutor
     * @param rsvc current instance of RuntimeServices
     * @param context The current context
     * @return return value from method, or null if no return value
     */
    public static Object invalidReferenceHandlerCall(
            EventHandlerMethodExecutor methodExecutor, 
            RuntimeServices rsvc,
            InternalContextAdapter context)
    {
        // app level cartridges have already been initialized
        EventCartridge ev1 = rsvc.getApplicationEventCartridge();
        Iterator applicationEventHandlerIterator = 
            (ev1 == null) ? null: ev1.getInvalidReferenceEventHandlers();              
        
        EventCartridge ev2 = context.getEventCartridge();
        initializeEventCartridge(rsvc, ev2);
        Iterator contextEventHandlerIterator = 
            (ev2 == null) ? null: ev2.getInvalidReferenceEventHandlers();              
        
        try
        {
            callEventHandlers(
                    applicationEventHandlerIterator, 
                    contextEventHandlerIterator, methodExecutor);
            
            return methodExecutor.getReturnValue();
        }
        catch (RuntimeException e)
        {
            throw e;
        }
        catch (Exception e)
        {
            throw ExceptionUtils.createRuntimeException("Exception in event handler.",e);
        }
        
    }

    /**
     * Initialize the event cartridge if appropriate.
     * 
     * @param rsvc current instance of RuntimeServices
     * @param eventCartridge the event cartridge to be initialized
     */
    private static void initializeEventCartridge(RuntimeServices rsvc, EventCartridge eventCartridge)
    {
        if (eventCartridge != null)
        {
            try
            {
                eventCartridge.initialize(rsvc);
            }
            catch (Exception e)
            {
                throw ExceptionUtils.createRuntimeException("Couldn't initialize event cartridge : ", e);
            }
        }
    }
    
    
    /**
     * Loop through both the application level and context-attached event handlers.
     * 
     * @param applicationEventHandlerIterator Iterator that loops through all global event handlers declared at application level
     * @param contextEventHandlerIterator Iterator that loops through all global event handlers attached to context
     * @param eventExecutor Strategy object that executes event handler method
     * @exception Exception generic exception potentially thrown by event handlers
     */
    private static void callEventHandlers(
            Iterator applicationEventHandlerIterator, 
            Iterator contextEventHandlerIterator,
            EventHandlerMethodExecutor eventExecutor)
    throws Exception
    {
        /**
         * First loop through the event handlers configured at the app level
         * in the properties file.
         */
        iterateOverEventHandlers(applicationEventHandlerIterator, eventExecutor);
        
        /**
         * Then loop through the event handlers attached to the context.
         */
        iterateOverEventHandlers(contextEventHandlerIterator, eventExecutor);
    }
    
    /**
     * Loop through a given iterator of event handlers.
     * 
     * @param handlerIterator Iterator that loops through event handlers
     * @param eventExecutor Strategy object that executes event handler method
     * @exception Exception generic exception potentially thrown by event handlers
     */
    private static void iterateOverEventHandlers(
            Iterator handlerIterator,
            EventHandlerMethodExecutor eventExecutor)
    throws Exception
    {
        if (handlerIterator != null)
        {
            for (Iterator i = handlerIterator; i.hasNext();)
            {
                EventHandler eventHandler = (EventHandler) i.next();
                
                if (!eventExecutor.isDone())
                {
                    eventExecutor.execute(eventHandler);
                }
            }            
        }
    }
    
}