/** Detect all HandlerMappings or just expect "handlerMapping" bean? */ private boolean detectAllHandlerMappings = true; /** Detect all HandlerAdapters or just expect "handlerAdapter" bean? */ private boolean detectAllHandlerAdapters = true; /** Detect all HandlerExceptionResolvers or just expect "handlerExceptionResolver" bean? */ private boolean detectAllHandlerExceptionResolvers = true; /** Detect all ViewResolvers or just expect "viewResolver" bean? */ private boolean detectAllViewResolvers = true; /** Perform cleanup of request attributes after include request? */ private boolean cleanupAfterInclude = true; /** MultipartResolver used by this servlet */ private MultipartResolver multipartResolver; /** LocaleResolver used by this servlet */ private LocaleResolver localeResolver; /** ThemeResolver used by this servlet */ private ThemeResolver themeResolver; /** List of HandlerMappings used by this servlet */ private List<HandlerMapping> handlerMappings; /** List of HandlerAdapters used by this servlet */ private List<HandlerAdapter> handlerAdapters; /** List of HandlerExceptionResolvers used by this servlet */ private List<HandlerExceptionResolver> handlerExceptionResolvers; /** RequestToViewNameTranslator used by this servlet */ private RequestToViewNameTranslator viewNameTranslator; /** FlashMapManager used by this servlet */ private FlashMapManager flashMapManager; /** List of ViewResolvers used by this servlet */ private List<ViewResolver> viewResolvers;初始化方法中，执行了组件的初始化
?
protected void initStrategies(ApplicationContext context) {
initMultipartResolver(context);
initLocaleResolver(context);
initThemeResolver(context);
initHandlerMappings(context);
initHandlerAdapters(context);
initHandlerExceptionResolvers(context);
initRequestToViewNameTranslator(context);
initViewResolvers(context);
initFlashMapManager(context);
}
?我们拿出initHandlerMappings(context)来瞅瞅
?
/**
* Initialize the HandlerMappings used by this class.
* <p>If no HandlerMapping beans are defined in the BeanFactory for this namespace,
* we default to BeanNameUrlHandlerMapping.
*/
private void initHandlerMappings(ApplicationContext context) {
this.handlerMappings = null;
if (this.detectAllHandlerMappings) {
// Find all HandlerMappings in the ApplicationContext, including ancestor contexts.
Map<String, HandlerMapping> matchingBeans =
BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);
if (!matchingBeans.isEmpty()) {
this.handlerMappings = new ArrayList<HandlerMapping>(matchingBeans.values());
// We keep HandlerMappings in sorted order.
OrderComparator.sort(this.handlerMappings);
}
}
else {
try {
HandlerMapping hm = context.getBean(HANDLER_MAPPING_BEAN_NAME, HandlerMapping.class);
this.handlerMappings = Collections.singletonList(hm);
}
catch (NoSuchBeanDefinitionException ex) {
// Ignore, we‘ll add a default HandlerMapping later.
}
}
// Ensure we have at least one HandlerMapping, by registering
// a default HandlerMapping if no other mappings are found.
if (this.handlerMappings == null) {
this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class);
if (logger.isDebugEnabled()) {
logger.debug("No HandlerMappings found in servlet ‘" + getServletName() + "‘: using default");
}
}
}
?通过该方法我们可以知道，当detectAllHandlerMappings为true时，直接到mvc容器及其父容器中寻找所有类型为HandlerMapping的bean，而detectAllHandlerMappings默认恰为true，因此我们完全可以不声明bean的id。当detectAllHandlerMappings为false时(可通过在web.xml里配置servlet参数来改变默认值)，则在mvc容器寻找名为"handlerMapping"的bean。如以上两种情况都没找到bean，将会实例化DispatcherServlet.properties中配置的bean。
? ? doService方法里有这么一段
?
// Keep a snapshot of the request attributes in case of an include,
// to be able to restore the original attributes after the include.
Map<String, Object> attributesSnapshot = null;
if (WebUtils.isIncludeRequest(request)) {
attributesSnapshot = new HashMap<String, Object>();
Enumeration<?> attrNames = request.getAttributeNames();
while (attrNames.hasMoreElements()) {
String attrName = (String) attrNames.nextElement();
if (this.cleanupAfterInclude || attrName.startsWith("org.springframework.web.servlet")) {
attributesSnapshot.put(attrName, request.getAttribute(attrName));
}
}
}
?这是用于对页面有include的情况做的请求数据快照处理。
下面进入重点doDispatch方法
?
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
HttpServletRequest processedRequest = request;
HandlerExecutionChain mappedHandler = null;
boolean multipartRequestParsed = false;
WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
try {
ModelAndView mv = null;
Exception dispatchException = null;
try {
// multipart包装处理，我们常用CommonsMultipartResolver
processedRequest = checkMultipart(request);
multipartRequestParsed = processedRequest != request;
// Determine handler for the current request.
mappedHandler = getHandler(processedRequest, false);
if (mappedHandler == null || mappedHandler.getHandler() == null) { // 404
noHandlerFound(processedRequest, response);
return;
}
// Determine handler adapter for the current request.
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
// Process last-modified header, if supported by the handler. // 代码省略
// 调用目标方法前，顺序执行拦截器
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
try {
// Actually invoke the handler.
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
}
finally {
if (asyncManager.isConcurrentHandlingStarted()) {
return;
}
}
applyDefaultViewName(request, mv);
// 调用目标方法后逆序执行拦截器
mappedHandler.applyPostHandle(processedRequest, response, mv);
}
catch (Exception ex) {
dispatchException = ex;
}
processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
}
catch (Exception ex) {
triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
}
catch (Error err) {
triggerAfterCompletionWithError(processedRequest, response, mappedHandler, err);
}
finally {
if (asyncManager.isConcurrentHandlingStarted()) {
// Instead of postHandle and afterCompletion
mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
return;
}
// Clean up any resources used by a multipart request.
if (multipartRequestParsed) {
cleanupMultipart(processedRequest);
}
}
}
?
HandlerExecutionChain?
boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
if (getInterceptors() != null) {
for (int i = 0; i < getInterceptors().length; i++) {
HandlerInterceptor interceptor = getInterceptors()[i];
if (!interceptor.preHandle(request, response, this.handler)) {
triggerAfterCompletion(request, response, null);
return false;
}
this.interceptorIndex = i;
}
}
return true;
}
/**
* Apply postHandle methods of registered interceptors.
*/
void applyPostHandle(HttpServletRequest request, HttpServletResponse response, ModelAndView mv) throws Exception {
if (getInterceptors() == null) {
return;
}
for (int i = getInterceptors().length - 1; i >= 0; i--) {
HandlerInterceptor interceptor = getInterceptors()[i];
interceptor.postHandle(request, response, this.handler, mv);
}
}
/**
* Trigger afterCompletion callbacks on the mapped HandlerInterceptors.
* Will just invoke afterCompletion for all interceptors whose preHandle invocation
* has successfully completed and returned true.
*/
void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, Exception ex)
throws Exception {
if (getInterceptors() == null) {
return;
}
for (int i = this.interceptorIndex; i >= 0; i--) {
HandlerInterceptor interceptor = getInterceptors()[i];
try {
interceptor.afterCompletion(request, response, this.handler, ex);
}
catch (Throwable ex2) {
logger.error("HandlerInterceptor.afterCompletion threw exception", ex2);
}
}
}
?
HandlerInterceptor
public interface HandlerInterceptor {
boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
throws Exception;
void postHandle(
HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
throws Exception;
void afterCompletion(
HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
throws Exception;
}
?
?自定义
public class ExceptionHandler implements HandlerExceptionResolver {
@Override
public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
request.setAttribute("exception",ex.getMessage());
ModelAndView mav = new ModelAndView();
mav.setViewName("/error");
return mav;
}
}
??
?
原文：http://wely.iteye.com/blog/2296899