詳解Spring Controller autowired Request變量
spring的DI大家比較熟悉了,對于依賴注入的實現也無須贅述。
那么spring的bean的默認scope為singleton,對于controller來說每次方法中均可以獲得request還是比較有意思的。
對于方法參數上的request通過構建方法的參數可以獲得最新的request
public final Object invokeForRequest(NativeWebRequest request, ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception { Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs); if (logger.isTraceEnabled()) { StringBuilder sb = new StringBuilder("Invoking ["); sb.append(getBeanType().getSimpleName()).append("."); sb.append(getMethod().getName()).append("] method with arguments "); sb.append(Arrays.asList(args)); logger.trace(sb.toString()); } Object returnValue = invoke(args); if (logger.isTraceEnabled()) { logger.trace("Method [" + getMethod().getName() + "] returned [" + returnValue + "]"); } return returnValue;}
2. 對于controller等單實例變量來說如何動態注入變量呢?spring使用了很聰明的辦法
/** * Register web-specific scopes ("request", "session", "globalSession", "application") * with the given BeanFactory, as used by the WebApplicationContext. * @param beanFactory the BeanFactory to configure * @param sc the ServletContext that we're running within */public static void registerWebApplicationScopes(ConfigurableListableBeanFactory beanFactory, ServletContext sc) { beanFactory.registerScope(WebApplicationContext.SCOPE_REQUEST, new RequestScope()); beanFactory.registerScope(WebApplicationContext.SCOPE_SESSION, new SessionScope(false)); beanFactory.registerScope(WebApplicationContext.SCOPE_GLOBAL_SESSION, new SessionScope(true)); if (sc != null) { ServletContextScope appScope = new ServletContextScope(sc); beanFactory.registerScope(WebApplicationContext.SCOPE_APPLICATION, appScope); // Register as ServletContext attribute, for ContextCleanupListener to detect it. sc.setAttribute(ServletContextScope.class.getName(), appScope); } beanFactory.registerResolvableDependency(ServletRequest.class, new RequestObjectFactory()); beanFactory.registerResolvableDependency(HttpSession.class, new SessionObjectFactory()); beanFactory.registerResolvableDependency(WebRequest.class, new WebRequestObjectFactory()); if (jsfPresent) { FacesDependencyRegistrar.registerFacesDependencies(beanFactory); }}
/** * Factory that exposes the current request object on demand. */ @SuppressWarnings("serial") private static class RequestObjectFactory implements ObjectFactory<ServletRequest>, Serializable { public ServletRequest getObject() { return currentRequestAttributes().getRequest(); } @Override public String toString() { return "Current HttpServletRequest"; } }
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