multiactioncontroller.java

spring api 源代码

		if (logger.isDebugEnabled()) {
			logger.debug("Found exception handler method [" + method + "]");
		}
	}


	//---------------------------------------------------------------------
	// Implementation of LastModified
	//---------------------------------------------------------------------

	/**
	 * Try to find an XXXXLastModified method, where XXXX is the name of a handler.
	 * Return -1 if there's no such handler, indicating that content must be updated.
	 * @see org.springframework.web.servlet.mvc.LastModified#getLastModified(HttpServletRequest)
	 */
	public long getLastModified(HttpServletRequest request) {
		try {
			String handlerMethodName = this.methodNameResolver.getHandlerMethodName(request);
			Method lastModifiedMethod = (Method) this.lastModifiedMethodMap.get(handlerMethodName);
			if (lastModifiedMethod != null) {
				try {
					// Invoke the last-modified method...
					Long wrappedLong = (Long) lastModifiedMethod.invoke(this.delegate, new Object[] {request});
					return (wrappedLong != null ? wrappedLong.longValue() : -1);
				}
				catch (Exception ex) {
					// We encountered an error invoking the last-modified method.
					// We can't do anything useful except log this, as we can't throw an exception.
					logger.error("Failed to invoke last-modified method", ex);
				}
			}
		}
		catch (NoSuchRequestHandlingMethodException ex) {
			// No handler method for this request. This shouldn't happen, as this
			// method shouldn't be called unless a previous invocation of this class
			// has generated content. Do nothing, that's OK: We'll return default.
		}
		return -1L;
	}


	//---------------------------------------------------------------------
	// Implementation of AbstractController
	//---------------------------------------------------------------------

	/**
	 * Determine a handler method and invoke it.
	 * @see MethodNameResolver#getHandlerMethodName
	 * @see #invokeNamedMethod
	 * @see #handleNoSuchRequestHandlingMethod
	 */
	protected ModelAndView handleRequestInternal(HttpServletRequest request, HttpServletResponse response)
			throws Exception {
		try {
			String methodName = this.methodNameResolver.getHandlerMethodName(request);
			return invokeNamedMethod(methodName, request, response);
		}
		catch (NoSuchRequestHandlingMethodException ex) {
			return handleNoSuchRequestHandlingMethod(ex, request, response);
		}
	}

	/**
	 * Handle the case where no request handler method was found.
	 * <p>The default implementation logs a warning and sends an HTTP 404 error.
	 * Alternatively, a fallback view could be chosen, or the
	 * NoSuchRequestHandlingMethodException could be rethrown as-is.
	 * @param ex the NoSuchRequestHandlingMethodException to be handled
	 * @param request current HTTP request
	 * @param response current HTTP response
	 * @return a ModelAndView to render, or <code>null</code> if handled directly
	 * @throws Exception an Exception that should be thrown as result of the servlet request
	 */
	protected ModelAndView handleNoSuchRequestHandlingMethod(
			NoSuchRequestHandlingMethodException ex, HttpServletRequest request, HttpServletResponse response)
			throws Exception {

		pageNotFoundLogger.warn(ex.getMessage());
		response.sendError(HttpServletResponse.SC_NOT_FOUND);
		return null;
	}

	/**
	 * Invokes the named method.
	 * <p>Uses a custom exception handler if possible; otherwise, throw an
	 * unchecked exception; wrap a checked exception or Throwable.
	 */
	protected final ModelAndView invokeNamedMethod(
			String methodName, HttpServletRequest request, HttpServletResponse response) throws Exception {

		Method method = (Method) this.handlerMethodMap.get(methodName);
		if (method == null) {
			throw new NoSuchRequestHandlingMethodException(methodName, getClass());
		}

		try {
			Class[] paramTypes = method.getParameterTypes();
			List params = new ArrayList(4);
			params.add(request);
			params.add(response);

			if (paramTypes.length >= 3 && paramTypes[2].equals(HttpSession.class)) {
				HttpSession session = request.getSession(false);
				if (session == null) {
					throw new HttpSessionRequiredException(
							"Pre-existing session required for handler method '" + methodName + "'");
				}
				params.add(session);
			}

			// If last parameter isn't of HttpSession type, it's a command.
			if (paramTypes.length >= 3 &&
					!paramTypes[paramTypes.length - 1].equals(HttpSession.class)) {
				Object command = newCommandObject(paramTypes[paramTypes.length - 1]);
				params.add(command);
				bind(request, command);
			}

			Object returnValue = method.invoke(this.delegate, params.toArray(new Object[params.size()]));
			return massageReturnValueIfNecessary(returnValue);
		}
		catch (InvocationTargetException ex) {
			// The handler method threw an exception.
			return handleException(request, response, ex.getTargetException());
		}
		catch (Exception ex) {
			// The binding process threw an exception.
			return handleException(request, response, ex);
		}
	}

	/**
	 * Processes the return value of a handler method to ensure that it either returns
	 * <code>null</code> or an instance of {@link ModelAndView}. When returning a {@link Map},
	 * the {@link Map} instance is wrapped in a new {@link ModelAndView} instance.
	 */
	private ModelAndView massageReturnValueIfNecessary(Object returnValue) {
		if (returnValue instanceof ModelAndView) {
			return (ModelAndView) returnValue;
		}
		else if (returnValue instanceof Map) {
			return new ModelAndView().addAllObjects((Map) returnValue);
		}
		else {
			// Either returned null or was 'void' return.
			// We'll assume that the handle method already wrote the response.
			return null;
		}
	}


	/**
	 * Create a new command object of the given class.
	 * <p>This implementation uses <code>BeanUtils.instantiateClass</code>,
	 * so commands need to have public no-arg constructors.
	 * Subclasses can override this implementation if desired.
	 * @throws Exception if the command object could not be instantiated
	 * @see org.springframework.beans.BeanUtils#instantiateClass(Class)
	 */
	protected Object newCommandObject(Class clazz) throws Exception {
		if (logger.isDebugEnabled()) {
			logger.debug("Creating new command of class [" + clazz.getName() + "]");
		}
		return BeanUtils.instantiateClass(clazz);
	}

	/**
	 * Bind request parameters onto the given command bean
	 * @param request request from which parameters will be bound
	 * @param command command object, that must be a JavaBean
	 * @throws Exception in case of invalid state or arguments
	 */
	protected void bind(HttpServletRequest request, Object command) throws Exception {
		logger.debug("Binding request parameters onto MultiActionController command");
		ServletRequestDataBinder binder = createBinder(request, command);
		binder.bind(request);
		if (this.validators != null) {
			for (int i = 0; i < this.validators.length; i++) {
				if (this.validators[i].supports(command.getClass())) {
					ValidationUtils.invokeValidator(this.validators[i], command, binder.getBindingResult());
				}
			}
		}
		binder.closeNoCatch();
	}

	/**
	 * Create a new binder instance for the given command and request.
	 * <p>Called by <code>bind</code>. Can be overridden to plug in custom
	 * ServletRequestDataBinder subclasses.
	 * <p>The default implementation creates a standard ServletRequestDataBinder,
	 * and invokes <code>initBinder</code>. Note that <code>initBinder</code>
	 * will not be invoked if you override this method!
	 * @param request current HTTP request
	 * @param command the command to bind onto
	 * @return the new binder instance
	 * @throws Exception in case of invalid state or arguments
	 * @see #bind
	 * @see #initBinder
	 */
	protected ServletRequestDataBinder createBinder(HttpServletRequest request, Object command) throws Exception {
		ServletRequestDataBinder binder = new ServletRequestDataBinder(command, getCommandName(command));
		initBinder(request, binder);
		return binder;
	}

	/**
	 * Return the command name to use for the given command object.
	 * <p>Default is "command".
	 * @param command the command object
	 * @return the command name to use
	 * @see #DEFAULT_COMMAND_NAME
	 */
	protected String getCommandName(Object command) {
		return DEFAULT_COMMAND_NAME;
	}

	/**
	 * Initialize the given binder instance, for example with custom editors.
	 * Called by <code>createBinder</code>.
	 * <p>This method allows you to register custom editors for certain fields of your
	 * command class. For instance, you will be able to transform Date objects into a
	 * String pattern and back, in order to allow your JavaBeans to have Date properties
	 * and still be able to set and display them in an HTML interface.
	 * <p>The default implementation is empty.
	 * <p>Note: the command object is not directly passed to this method, but it's available
	 * via {@link org.springframework.validation.DataBinder#getTarget()}
	 * @param request current HTTP request
	 * @param binder new binder instance
	 * @throws Exception in case of invalid state or arguments
	 * @see #createBinder
	 * @see org.springframework.validation.DataBinder#registerCustomEditor
	 * @see org.springframework.beans.propertyeditors.CustomDateEditor
	 */
	protected void initBinder(HttpServletRequest request, ServletRequestDataBinder binder) throws Exception {
		initBinder((ServletRequest) request, binder);
	}

	/**
	 * Initialize the given binder instance, for example with custom editors.
	 * @deprecated as of Spring 2.0:
	 * use <code>initBinder(HttpServletRequest, ServletRequestDataBinder)</code> instead
	 */
	protected void initBinder(ServletRequest request, ServletRequestDataBinder binder) throws Exception {
	}


	/**
	 * Determine the exception handler method for the given exception.
	 * <p>Can return <code>null</code> if not found.
	 * @return a handler for the given exception type, or <code>null</code>
	 * @param exception the exception to handle
	 */
	protected Method getExceptionHandler(Throwable exception) {
		Class exceptionClass = exception.getClass();
		if (logger.isDebugEnabled()) {
			logger.debug("Trying to find handler for exception class [" + exceptionClass.getName() + "]");
		}
		Method handler = (Method) this.exceptionHandlerMap.get(exceptionClass);
		while (handler == null && !exceptionClass.equals(Throwable.class)) {
			if (logger.isDebugEnabled()) {
				logger.debug("Trying to find handler for exception superclass [" + exceptionClass.getName() + "]");
			}
			exceptionClass = exceptionClass.getSuperclass();
			handler = (Method) this.exceptionHandlerMap.get(exceptionClass);
		}
		return handler;
	}

	/**
	 * We've encountered an exception thrown from a handler method.
	 * Invoke an appropriate exception handler method, if any.
	 * @param request current HTTP request
	 * @param response current HTTP response
	 * @param ex the exception that got thrown
	 * @return a ModelAndView to render the response
	 */
	private ModelAndView handleException(HttpServletRequest request, HttpServletResponse response, Throwable ex)
			throws Exception {

		Method handler = getExceptionHandler(ex);
		if (handler != null) {
			return invokeExceptionHandler(handler, request, response, ex);
		}
		// If we get here, there was no custom handler
		if (ex instanceof Exception) {
			throw (Exception) ex;
		}
		if (ex instanceof Error) {
			throw (Error) ex;
		}
		// Should never happen!
		throw new NestedServletException("Unknown Throwable type encountered", ex);
	}

	/**
	 * Invoke the selected exception handler.
	 * @param handler handler method to invoke
	 */
	private ModelAndView invokeExceptionHandler(
			Method handler, HttpServletRequest request, HttpServletResponse response, Throwable ex)
			throws Exception {

		// If we get here, we have a handler.
		if (logger.isDebugEnabled()) {
			logger.debug("Invoking exception handler [" + handler + "] for exception [" + ex + "]");
		}
		try {
			Object returnValue = handler.invoke(this.delegate, new Object[] {request, response, ex});
			return massageReturnValueIfNecessary(returnValue);
		}
		catch (InvocationTargetException ex2) {
			Throwable targetEx = ex2.getTargetException();
			if (targetEx instanceof Exception) {
				throw (Exception) targetEx;
			}
			if (targetEx instanceof Error) {
				throw (Error) targetEx;
			}
			// Should never happen!
			throw new NestedServletException("Unknown Throwable type encountered", targetEx);
		}
	}

}