frameworkservlet.java

一个关于Spring框架的示例应用程序,简单使用,可以参考.

		if (logger.isInfoEnabled()) {
			long elapsedTime = System.currentTimeMillis() - startTime;
			logger.info("FrameworkServlet '" + getServletName() + "': initialization completed in " +
					elapsedTime + " ms");
		}
	}

	/**
	 * Initialize and publish the WebApplicationContext for this servlet.
	 * Delegates to createWebApplicationContext for actual creation.
	 * Can be overridden in subclasses.
	 * @throws BeansException if the context couldn't be initialized
	 * @see #createWebApplicationContext
	 */
	protected WebApplicationContext initWebApplicationContext() throws BeansException {
		getServletContext().log(
				"Loading WebApplicationContext for Spring FrameworkServlet '" + getServletName() + "'");

		WebApplicationContext parent = WebApplicationContextUtils.getWebApplicationContext(getServletContext());
		WebApplicationContext wac = createWebApplicationContext(parent);
		if (logger.isInfoEnabled()) {
			logger.info("Using context class [" + wac.getClass().getName() + "] for servlet '" +
					getServletName() + "'");
		}

		if (isPublishContext()) {
			// Publish the context as a servlet context attribute.
			String attrName = getServletContextAttributeName();
			getServletContext().setAttribute(attrName, wac);
			if (logger.isDebugEnabled()) {
				logger.debug("Published WebApplicationContext of servlet '" + getServletName() +
						"' as ServletContext attribute with name [" + attrName + "]");
			}
		}

		return wac;
	}

	/**
	 * Instantiate the WebApplicationContext for this servlet, either a default
	 * XmlWebApplicationContext or a custom context class if set. This implementation
	 * expects custom contexts to implement ConfigurableWebApplicationContext.
	 * Can be overridden in subclasses.
	 * @throws BeansException if the context couldn't be initialized
	 * @see #setContextClass
	 * @see org.springframework.web.context.support.XmlWebApplicationContext
	 */
	protected WebApplicationContext createWebApplicationContext(WebApplicationContext parent)
			throws BeansException {

		if (logger.isDebugEnabled()) {
			logger.debug("Servlet with name '" + getServletName() +
					"' will try to create custom WebApplicationContext context of class '" +
					getContextClass().getName() + "'" + ", using parent context [" + parent + "]");
		}
		if (!ConfigurableWebApplicationContext.class.isAssignableFrom(getContextClass())) {
			throw new ApplicationContextException(
					"Fatal initialization error in servlet with name '" + getServletName() +
					"': custom WebApplicationContext class [" + getContextClass().getName() +
					"] is not of type ConfigurableWebApplicationContext");
		}

		ConfigurableWebApplicationContext wac =
				(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(getContextClass());
		wac.setParent(parent);
		wac.setServletContext(getServletContext());
		wac.setNamespace(getNamespace());
		if (getContextConfigLocation() != null) {
			wac.setConfigLocations(
			    StringUtils.tokenizeToStringArray(
							getContextConfigLocation(), ConfigurableWebApplicationContext.CONFIG_LOCATION_DELIMITERS));
		}
		wac.refresh();
		return wac;
	}

	/**
	 * Return the ServletContext attribute name for this servlet's WebApplicationContext.
	 * Default implementation returns SERVLET_CONTEXT_PREFIX + servlet name.
	 * @see #SERVLET_CONTEXT_PREFIX
	 * @see #getServletName
	 */
	public String getServletContextAttributeName() {
		return SERVLET_CONTEXT_PREFIX + getServletName();
	}

	/**
	 * Return this servlet's WebApplicationContext.
	 */
	public final WebApplicationContext getWebApplicationContext() {
		return webApplicationContext;
	}

	/**
	 * This method will be invoked after any bean properties have been set and
	 * the WebApplicationContext has been loaded. The default implementation is empty;
	 * subclasses may override this method to perform any initialization they require.
	 * @throws ServletException in case of an initialization exception
	 * @throws BeansException if thrown by ApplicationContext methods
	 */
	protected void initFrameworkServlet() throws ServletException, BeansException {
	}


	/**
	 * Delegate GET requests to serviceWrapper/doService.
	 * <p>Will also be invoked by HttpServlet's default implementation of doHead,
	 * with a NoBodyResponse that just captures the content length.
	 * @see #doService
	 * @see #doHead
	 */
	protected final void doGet(HttpServletRequest request, HttpServletResponse response)
	    throws ServletException, IOException {
		serviceWrapper(request, response);
	}

	/**
	 * Delegate POST requests to serviceWrapper/doService.
	 * @see #doService
	 */
	protected final void doPost(HttpServletRequest request, HttpServletResponse response)
	    throws ServletException, IOException {
		serviceWrapper(request, response);
	}

	/**
	 * Delegate PUT requests to serviceWrapper/doService.
	 * @see #doService
	 */
	protected final void doPut(HttpServletRequest request, HttpServletResponse response)
	    throws ServletException, IOException {
		serviceWrapper(request, response);
	}

	/**
	 * Delegate DELETE requests to serviceWrapper/doService.
	 * @see #doService
	 */
	protected final void doDelete(HttpServletRequest request, HttpServletResponse response)
	    throws ServletException, IOException {
		serviceWrapper(request, response);
	}

	/**
	 * Handle this request, publishing an event regardless of the outcome.
	 * The actually event handling is performed by the abstract doService() method.
	 */
	private void serviceWrapper(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		long startTime = System.currentTimeMillis();
		Exception failureCause = null;
		try {
			doService(request, response);
		}
		catch (ServletException ex) {
			failureCause = ex;
			throw ex;
		}
		catch (IOException ex) {
			failureCause = ex;
			throw ex;
		}
		catch (RuntimeException ex) {
			failureCause = ex;
			throw ex;
		}
		catch (Exception ex) {
			failureCause = ex;
			throw new ServletException(ex.getMessage(), ex);
		}
		finally {
			if (failureCause != null) {
				logger.error("Could not complete request", failureCause);
			}
			else {
				logger.debug("Successfully completed request");
			}
			if (isPublishEvents()) {
				// Whether or not we succeeded, publish an event.
				long processingTime = System.currentTimeMillis() - startTime;
				this.webApplicationContext.publishEvent(
						new RequestHandledEvent(this, request.getRequestURI(), processingTime, request.getRemoteAddr(),
								request.getMethod(), getServletConfig().getServletName(), WebUtils.getSessionId(request),
								getUsernameForRequest(request), failureCause));
			}
		}
	}

	/**
	 * Determine the username for the given request.
	 * Default implementation takes the name of the UserPrincipal, if any.
	 * Can be overridden in subclasses.
	 * @param request current HTTP request
	 * @return the username, or null if none
	 * @see javax.servlet.http.HttpServletRequest#getUserPrincipal
	 */
	protected String getUsernameForRequest(HttpServletRequest request) {
		Principal userPrincipal = request.getUserPrincipal();
		return (userPrincipal != null ? userPrincipal.getName() : null);
	}

	/**
	 * Subclasses must implement this method to do the work of request handling.
	 * The contract is the same as that for the doGet or doPost methods of HttpServlet.
	 * This class intercepts calls to ensure that event publication takes place.
	 * @param request current HTTP request
	 * @param response current HTTP response
	 * @throws Exception in case of any kind of processing failure
	 * @see javax.servlet.http.HttpServlet#doGet
	 * @see javax.servlet.http.HttpServlet#doPost
	 */
	protected abstract void doService(HttpServletRequest request, HttpServletResponse response)
	    throws Exception;


	/**
	 * Close the WebApplicationContext of this servlet.
	 * @see org.springframework.context.ConfigurableApplicationContext#close
	 */
	public void destroy() {
		getServletContext().log(
				"Closing WebApplicationContext of Spring FrameworkServlet '" + getServletName() + "'");
		if (this.webApplicationContext instanceof ConfigurableApplicationContext) {
			((ConfigurableApplicationContext) this.webApplicationContext).close();
		}
	}

}