一、拦截器
SpringMVC提供了拦截器在处理请求之前,之后,渲染视图后执行逻辑处理。接口是HandlerInterceptor。preHandle方法在处理请求之前执行,postHandle方法是在处理请求后渲染视图视图之前执行。afterCompletion方法在渲染视图后执行。
二、解析interceptor
<mvc:interceptors>
<mvc:interceptor>
<mvc:mapping path="/*"/>
<bean id="myInteceptor" class="mvc.inteceptor.MyInteceptor"/>
</mvc:interceptor>
</mvc:interceptors>
interceptor标签由InterceptorsBeanDefinitionParser解析。
InterceptorsBeanDefinitionParser.parse(Element element, ParserContext context)
public BeanDefinition parse(Element element, ParserContext context) {
context.pushContainingComponent(
new CompositeComponentDefinition(element.getTagName(), context.extractSource(element)));
RuntimeBeanReference pathMatcherRef = null;
if (element.hasAttribute("path-matcher")) {
pathMatcherRef = new RuntimeBeanReference(element.getAttribute("path-matcher"));
}
List<Element> interceptors = DomUtils.getChildElementsByTagName(element, "bean", "ref", "interceptor");
for (Element interceptor : interceptors) {
RootBeanDefinition mappedInterceptorDef = new RootBeanDefinition(MappedInterceptor.class);
mappedInterceptorDef.setSource(context.extractSource(interceptor));
mappedInterceptorDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
ManagedList<String> includePatterns = null;
ManagedList<String> excludePatterns = null;
Object interceptorBean;
if ("interceptor".equals(interceptor.getLocalName())) {
includePatterns = getIncludePatterns(interceptor, "mapping");
excludePatterns = getIncludePatterns(interceptor, "exclude-mapping");
Element beanElem = DomUtils.getChildElementsByTagName(interceptor, "bean", "ref").get(0);
interceptorBean = context.getDelegate().parsePropertySubElement(beanElem, null);
}
else {
interceptorBean = context.getDelegate().parsePropertySubElement(interceptor, null);
}
mappedInterceptorDef.getConstructorArgumentValues().addIndexedArgumentValue(0, includePatterns);
mappedInterceptorDef.getConstructorArgumentValues().addIndexedArgumentValue(1, excludePatterns);
mappedInterceptorDef.getConstructorArgumentValues().addIndexedArgumentValue(2, interceptorBean);
if (pathMatcherRef != null) {
mappedInterceptorDef.getPropertyValues().add("pathMatcher", pathMatcherRef);
}
String beanName = context.getReaderContext().registerWithGeneratedName(mappedInterceptorDef);
context.registerComponent(new BeanComponentDefinition(mappedInterceptorDef, beanName));
}
context.popAndRegisterContainingComponent();
return null;
}
将每个interceptor元素解析成MappedInterceptor。
三、执行拦截器
RequestMappingHandlerMapping继承了ApplicationObjectSupport抽象类,ApplicationObjectSupport实现了ApplicationContextAware接口。在实例化RequestMappingHandlerMapping会调用ApplicationContextAware.setApplicationContext方法。会调用到AbstractHandlerMapping.initApplicationContext():
protected void initApplicationContext() throws BeansException {
extendInterceptors(this.interceptors);
detectMappedInterceptors(this.adaptedInterceptors);
initInterceptors();
}
protected void detectMappedInterceptors(List<HandlerInterceptor> mappedInterceptors) {
mappedInterceptors.addAll(BeanFactoryUtils.beansOfTypeIncludingAncestors(
obtainApplicationContext(), MappedInterceptor.class, true, false).values());
}
detectMappedInterceptors从beanFactory中获取类型为MappedInterceptor的所有bean并加入mappedInterceptors集合中.
DispatcherServlet在处理请求获取handle时,会调用AbstractHandlerMapping.getHandlerExecutionChain
protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {
HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ?
(HandlerExecutionChain) handler : new HandlerExecutionChain(handler));
for (HandlerInterceptor interceptor : this.adaptedInterceptors) {
if (interceptor instanceof MappedInterceptor) {
MappedInterceptor mappedInterceptor = (MappedInterceptor) interceptor;
if (mappedInterceptor.matches(request)) {
chain.addInterceptor(mappedInterceptor.getInterceptor());
}
}
else {
chain.addInterceptor(interceptor);
}
}
return chain;
}
遍历adaptedInterceptors集合,如果HandlerInterceptor是MappedInterceptor类型,则判断MappedInterceptor是否匹配请求,如果匹配则加入HandlerExecutionChain。通过在配置拦截器mvc:mapping的path和请求路径是否匹配来判断MappedInterceptor是否匹配请求。如果HandlerInterceptor不是MappedInterceptor类型则加入HandlerExecutionChain。
DispatcherServlet.doDispatch(HttpServletRequest request, HttpServletResponse response)处理请求时:
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 {
processedRequest = checkMultipart(request);
multipartRequestParsed = (processedRequest != request);
// Determine handler for the current request.
mappedHandler = getHandler(processedRequest);
if (mappedHandler == null) {
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.
String method = request.getMethod();
boolean isGet = "GET".equals(method);
if (isGet || "HEAD".equals(method)) {
long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
return;
}
}
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
// Actually invoke the handler.
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
if (asyncManager.isConcurrentHandlingStarted()) {
return;
}
applyDefaultViewName(processedRequest, mv);
mappedHandler.applyPostHandle(processedRequest, response, mv);
}
catch (Exception ex) {
dispatchException = ex;
}
catch (Throwable err) {
// As of 4.3, we're processing Errors thrown from handler methods as well,
// making them available for @ExceptionHandler methods and other scenarios.
dispatchException = new NestedServletException("Handler dispatch failed", err);
}
processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
}
catch (Exception ex) {
triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
}
catch (Throwable err) {
triggerAfterCompletion(processedRequest, response, mappedHandler,
new NestedServletException("Handler processing failed", err));
}
finally {
if (asyncManager.isConcurrentHandlingStarted()) {
// Instead of postHandle and afterCompletion
if (mappedHandler != null) {
mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
}
}
else {
// Clean up any resources used by a multipart request.
if (multipartRequestParsed) {
cleanupMultipart(processedRequest);
}
}
}
}
调用getHandler获取HandlerExecutionChain后,调用mappedHandler.applyPreHandle(processedRequest, response)执行拦截器的preHandle方法,如果有一个拦截器返回false,则退出。调用HandlerAdapter.handle执行实际处理请求。在调用mappedHandler.applyPostHandle逆序执行拦截器postHandle的方法。processDispatchResult渲染视图和处理异常完成后调用mappedHandler.triggerAfterCompletion执行拦截器的afterCompletion方法。
标签:拦截器,SpringMVC,mappedHandler,request,interceptor,null,response,processedRequest From: https://www.cnblogs.com/shigongp/p/16906836.html