simplemappingexceptionresolver.java

spring api 源代码

					}
				}
			}
		}
		// Else only apply if there are no explicit handler mappings.
		return (this.mappedHandlers == null && this.mappedHandlerClasses == null);
	}

	/**
	 * Actually resolve the given exception that got thrown during on handler execution,
	 * returning a ModelAndView that represents a specific error page if appropriate.
	 * <p>May be overridden in subclasses, in order to apply specific exception checks.
	 * Note that this template method will be invoked <i>after</i> checking whether
	 * this resolved applies ("mappedHandlers" etc), so an implementation may simply
	 * proceed with its actual exception handling.
	 * @param request current HTTP request
	 * @param response current HTTP response
	 * @param handler the executed handler, or <code>null</code> if none chosen at the
	 * time of the exception (for example, if multipart resolution failed)
	 * @param ex the exception that got thrown during handler execution
	 * @return a corresponding ModelAndView to forward to, or <code>null</code> for default processing
	 */
	protected ModelAndView doResolveException(
			HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {

		// Log exception, both at debug log level and at warn level, if desired.
		if (logger.isDebugEnabled()) {
			logger.debug("Resolving exception from handler [" + handler + "]: " + ex);
		}
		logException(ex, request);

		// Expose ModelAndView for chosen error view.
		String viewName = determineViewName(ex, request);
		if (viewName != null) {
			// Apply HTTP status code for error views, if specified.
			// Only apply it if we're processing a top-level request.
			Integer statusCode = determineStatusCode(request, viewName);
			if (statusCode != null) {
				applyStatusCodeIfPossible(request, response, statusCode.intValue());
			}
			return getModelAndView(viewName, ex, request);
		}
		else {
			return null;
		}
	}


	/**
	 * Log the given exception at warn level, provided that warn logging has been
	 * activated through the {@link #setWarnLogCategory "warnLogCategory"} property.
	 * <p>Calls {@link #buildLogMessage} in order to determine the concrete message
	 * to log. Always passes the full exception to the logger.
	 * @param ex the exception that got thrown during handler execution
	 * @param request current HTTP request (useful for obtaining metadata)
	 * @see #setWarnLogCategory
	 * @see #buildLogMessage
	 * @see org.apache.commons.logging.Log#warn(Object, Throwable)
	 */
	protected void logException(Exception ex, HttpServletRequest request) {
		if (this.warnLogger != null && this.warnLogger.isWarnEnabled()) {
			this.warnLogger.warn(buildLogMessage(ex, request), ex);
		}
	}

	/**
	 * Build a log message for the given exception, occured during processing
	 * the given request.
	 * @param ex the exception that got thrown during handler execution
	 * @param request current HTTP request (useful for obtaining metadata)
	 * @return the log message to use
	 */
	protected String buildLogMessage(Exception ex, HttpServletRequest request) {
		return "Handler execution resulted in exception";
	}


	/**
	 * Determine the view name for the given exception, searching the
	 * {@link #setExceptionMappings "exceptionMappings"}, using the
	 * {@link #setDefaultErrorView "defaultErrorView"} as fallback.
	 * @param ex the exception that got thrown during handler execution
	 * @param request current HTTP request (useful for obtaining metadata)
	 * @return the resolved view name, or <code>null</code> if none found
	 */
	protected String determineViewName(Exception ex, HttpServletRequest request) {
		String viewName = null;
		// Check for specific exception mappings.
		if (this.exceptionMappings != null) {
			viewName = findMatchingViewName(this.exceptionMappings, ex);
		}
		// Return default error view else, if defined.
		if (viewName == null && this.defaultErrorView != null) {
			if (logger.isDebugEnabled()) {
				logger.debug("Resolving to default view '" + this.defaultErrorView +
						"' for exception of type [" + ex.getClass().getName() + "]");
			}
			viewName = this.defaultErrorView;
		}
		return viewName;
	}

	/**
	 * Find a matching view name in the given exception mappings.
	 * @param exceptionMappings mappings between exception class names and error view names
	 * @param ex the exception that got thrown during handler execution
	 * @return the view name, or <code>null</code> if none found
	 * @see #setExceptionMappings
	 */
	protected String findMatchingViewName(Properties exceptionMappings, Exception ex) {
		String viewName = null;
		String dominantMapping = null;
		int deepest = Integer.MAX_VALUE;
		for (Enumeration names = exceptionMappings.propertyNames(); names.hasMoreElements();) {
			String exceptionMapping = (String) names.nextElement();
			int depth = getDepth(exceptionMapping, ex);
			if (depth >= 0 && depth < deepest) {
				deepest = depth;
				dominantMapping = exceptionMapping;
				viewName = exceptionMappings.getProperty(exceptionMapping);
			}
		}
		if (viewName != null && logger.isDebugEnabled()) {
			logger.debug("Resolving to view '" + viewName + "' for exception of type [" + ex.getClass().getName() +
					"], based on exception mapping [" + dominantMapping + "]");
		}
		return viewName;
	}

	/**
	 * Return the depth to the superclass matching.
	 * <p>0 means ex matches exactly. Returns -1 if there's no match.
	 * Otherwise, returns depth. Lowest depth wins.
	 * <p>Follows the same algorithm as
	 * {@link org.springframework.transaction.interceptor.RollbackRuleAttribute}.
	 */
	protected int getDepth(String exceptionMapping, Exception ex) {
		return getDepth(exceptionMapping, ex.getClass(), 0);
	}

	private int getDepth(String exceptionMapping, Class exceptionClass, int depth) {
		if (exceptionClass.getName().indexOf(exceptionMapping) != -1) {
			// Found it!
			return depth;
		}
		// If we've gone as far as we can go and haven't found it...
		if (exceptionClass.equals(Throwable.class)) {
			return -1;
		}
		return getDepth(exceptionMapping, exceptionClass.getSuperclass(), depth + 1);
	}


	/**
	 * Determine the HTTP status code to apply for the given error view.
	 * <p>The default implementation always returns the specified
	 * {@link #setDefaultStatusCode "defaultStatusCode"}, as a common
	 * status code for all error views. Override this in a custom subclass
	 * to determine a specific status code for the given view.
	 * @param request current HTTP request
	 * @param viewName the name of the error view
	 * @return the HTTP status code to use, or <code>null</code> for the
	 * servlet container's default (200 in case of a standard error view)
	 * @see #setDefaultStatusCode
	 * @see #applyStatusCodeIfPossible
	 */
	protected Integer determineStatusCode(HttpServletRequest request, String viewName) {
		return this.defaultStatusCode;
	}

	/**
	 * Apply the specified HTTP status code to the given response, if possible
	 * (that is, if not executing within an include request).
	 * @param request current HTTP request
	 * @param response current HTTP response
	 * @param statusCode the status code to apply
	 * @see #determineStatusCode
	 * @see #setDefaultStatusCode
	 * @see javax.servlet.http.HttpServletResponse#setStatus
	 */
	protected void applyStatusCodeIfPossible(HttpServletRequest request, HttpServletResponse response, int statusCode) {
		if (!WebUtils.isIncludeRequest(request)) {
			if (logger.isDebugEnabled()) {
				logger.debug("Applying HTTP status code " + statusCode);
			}
			response.setStatus(statusCode);
		}
	}

	/**
	 * Return a ModelAndView for the given request, view name and exception.
	 * <p>The default implementation delegates to {@link #getModelAndView(String, Exception)}.
	 * @param viewName the name of the error view
	 * @param ex the exception that got thrown during handler execution
	 * @param request current HTTP request (useful for obtaining metadata)
	 * @return the ModelAndView instance
	 */
	protected ModelAndView getModelAndView(String viewName, Exception ex, HttpServletRequest request) {
		return getModelAndView(viewName, ex);
	}

	/**
	 * Return a ModelAndView for the given view name and exception.
	 * <p>The default implementation adds the specified exception attribute.
	 * Can be overridden in subclasses.
	 * @param viewName the name of the error view
	 * @param ex the exception that got thrown during handler execution
	 * @return the ModelAndView instance
	 * @see #setExceptionAttribute
	 */
	protected ModelAndView getModelAndView(String viewName, Exception ex) {
		ModelAndView mv = new ModelAndView(viewName);
		if (this.exceptionAttribute != null) {
			if (logger.isDebugEnabled()) {
				logger.debug("Exposing Exception as model attribute '" + this.exceptionAttribute + "'");
			}
			mv.addObject(this.exceptionAttribute, ex);
		}
		return mv;
	}

}