@Autowired注入的Httprequest如何保证线程安全

@Autowired基于JDK动态代理对象

AutowireUtils.ObjectFactoryDelegatingInvocationHandler

AutowireUtils：
	
	private static class ObjectFactoryDelegatingInvocationHandler implements InvocationHandler, Serializable {

		private final ObjectFactory objectFactory;
		public ObjectFactoryDelegatingInvocationHandler(ObjectFactory objectFactory) {
			this.objectFactory = objectFactory;
		}

		@Override
		public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
			String methodName = method.getName();
			if (methodName.equals("equals")) {
				return (proxy == args[0]);
			} else if (methodName.equals("hashCode")) {
				return System.identityHashCode(proxy);
			} else if (methodName.equals("toString")) {
				return this.objectFactory.toString();
			}
		
			// 执行目标方法。注意：目标实例对象是objectFactory.getObject()
			try {
				return method.invoke(this.objectFactory.getObject(), args);
			} catch (InvocationTargetException ex) {
				throw ex.getTargetException();
			}
		}
	}

 spring中，请求统一处理入口，在这里获取HttpRequest

protected final void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        long startTime = System.currentTimeMillis();
        Throwable failureCause = null;
        LocaleContext previousLocaleContext = LocaleContextHolder.getLocaleContext();
        LocaleContext localeContext = this.buildLocaleContext(request);
        RequestAttributes previousAttributes = RequestContextHolder.getRequestAttributes();
        ServletRequestAttributes requestAttributes = this.buildRequestAttributes(request, response, previousAttributes);
        WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
        asyncManager.registerCallableInterceptor(FrameworkServlet.class.getName(), new FrameworkServlet.RequestBindingInterceptor());
        this.initContextHolders(request, localeContext, requestAttributes);

        try {
            this.doService(request, response);
        } catch (IOException | ServletException var16) {
            failureCause = var16;
            throw var16;
        } catch (Throwable var17) {
            failureCause = var17;
            throw new NestedServletException("Request processing failed", var17);
        } finally {
            this.resetContextHolders(request, previousLocaleContext, previousAttributes);
            if (requestAttributes != null) {
                requestAttributes.requestCompleted();
            }

            this.logResult(request, response, (Throwable)failureCause, asyncManager);
            this.publishRequestHandledEvent(request, response, startTime, (Throwable)failureCause);
        }

    }

public static void registerWebApplicationScopes(ConfigurableListableBeanFactory beanFactory, @Nullable ServletContext sc) {
        beanFactory.registerScope("request", new RequestScope());
        beanFactory.registerScope("session", new SessionScope());
        if (sc != null) {
            ServletContextScope appScope = new ServletContextScope(sc);
            beanFactory.registerScope("application", appScope);
            sc.setAttribute(ServletContextScope.class.getName(), appScope);
        }

        beanFactory.registerResolvableDependency(ServletRequest.class, new WebApplicationContextUtils.RequestObjectFactory());
        beanFactory.registerResolvableDependency(ServletResponse.class, new WebApplicationContextUtils.ResponseObjectFactory());
        beanFactory.registerResolvableDependency(HttpSession.class, new WebApplicationContextUtils.SessionObjectFactory());
        beanFactory.registerResolvableDependency(WebRequest.class, new WebApplicationContextUtils.WebRequestObjectFactory());
        if (jsfPresent) {
            WebApplicationContextUtils.FacesDependencyRegistrar.registerFacesDependencies(beanFactory);
        }

    }

private static class RequestObjectFactory implements ObjectFactory, Serializable {
        private RequestObjectFactory() {
        }

        public ServletRequest getObject() {
            return WebApplicationContextUtils.currentRequestAttributes().getRequest();
        }

        public String toString() {
            return "Current HttpServletRequest";
        }
    }

WebApplicationContextUtils.currentRequestAttributes().getRequest()

private static ServletRequestAttributes currentRequestAttributes() {
        RequestAttributes requestAttr = RequestContextHolder.currentRequestAttributes();
        if (!(requestAttr instanceof ServletRequestAttributes)) {
            throw new IllegalStateException("Current request is not a servlet request");
        } else {
            return (ServletRequestAttributes)requestAttr;
        }
    }

 RequestContextHolder.currentRequestAttributes()作用于全局

@Nullable
    public static RequestAttributes getRequestAttributes() {
        RequestAttributes attributes = (RequestAttributes)requestAttributesHolder.get();
        if (attributes == null) {
            attributes = (RequestAttributes)inheritableRequestAttributesHolder.get();
        }

        return attributes;
    }

看下requestAttributesHolder是什么

private static final ThreadLocal requestAttributesHolder
 = new NamedThreadLocal("Request attributes");
    

public T get() {
        Thread t = Thread.currentThread();
        ThreadLocalMap map = getMap(t);
        if (map != null) {
            ThreadLocalMap.Entry e = map.getEntry(this);
            if (e != null) {
                @SuppressWarnings("unchecked")
                T result = (T)e.value;
                return result;
            }
        }
        return setInitialValue();
    }

 1、是通过threadLocal来进行httprequest获取的，可以保证线程安全

 2、Spring何时把Request信息放进RequestContextHolder？

3、RequestContextHolder作用于全局要想找到何时向RequestContextHolder里放值的，仅需知道何时调用的set方法便可

FrameworkServlet：

private void initContextHolders(HttpServletRequest request, @Nullable LocaleContext localeContext, @Nullable RequestAttributes requestAttributes) {
        if (localeContext != null) {
            LocaleContextHolder.setLocaleContext(localeContext, this.threadContextInheritable);
        }

        if (requestAttributes != null) {
            RequestContextHolder.setRequestAttributes(requestAttributes, this.threadContextInheritable);
        }

    }

protected final void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        RequestAttributes previousAttributes = RequestContextHolder.getRequestAttributes();
        ServletRequestAttributes requestAttributes = this.buildRequestAttributes(request, response, previousAttributes);
        WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
        asyncManager.registerCallableInterceptor(FrameworkServlet.class.getName(), new FrameworkServlet.RequestBindingInterceptor());
        this.initContextHolders(request, localeContext, requestAttributes);

    }