#####################更新:

SpringMVC的请求处理过程中的路径匹配过程:

org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#lookupHandlerMethod
(spring-webmvc-4.2.3.RELEASE

路径匹配的过程中有如下代码:

List<Match> matches = new ArrayList<Match>();
List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
if (directPathMatches != null) {
   addMatchingMappings(directPathMatches, matches, request);
}
if (matches.isEmpty()) {
   // No choice but to go through all mappings...
   addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request);
}

SpringMVC首先对HTTP请求中的path与已注册的RequestMappingInfo(经解析的@RequestMapping)中的path进行一个完全匹配来查找对应的HandlerMethod,即处理该请求的方法,**这个匹配就是一个Map#get方法**。若找不到则会遍历所有的RequestMappingInfo进行查找。这个查找是不会提前停止的,直到遍历完全部的RequestMappingInfo。

这里主要是springmvc在项目启动时根据requestMapping中api的访问路径封装了不同的map对象,对于纯path请求就是从map中直接get,而对于使用了pathVariable注解的请求则需要去map对象中找到所有满足条件的对象然后取最优解。

public RequestMappingInfo getMatchingCondition(HttpServletRequest request) {
    RequestMethodsRequestCondition methods = this.methodsCondition.getMatchingCondition(request);
    ParamsRequestCondition params = this.paramsCondition.getMatchingCondition(request);
    HeadersRequestCondition headers = this.headersCondition.getMatchingCondition(request);
    ConsumesRequestCondition consumes = this.consumesCondition.getMatchingCondition(request);
    ProducesRequestCondition produces = this.producesCondition.getMatchingCondition(request);

    if (methods == null || params == null || headers == null || consumes == null || produces == null) {
        if (CorsUtils.isPreFlightRequest(request)) {
            methods = getAccessControlRequestMethodCondition(request);
            if (methods == null || params == null) {
                return null;
            }
        }
        else {
            return null;
        }
    }

    PatternsRequestCondition patterns = this.patternsCondition.getMatchingCondition(request);
    if (patterns == null) {
        return null;
    }

    RequestConditionHolder custom = this.customConditionHolder.getMatchingCondition(request);
    if (custom == null) {
        return null;
    }

    return new RequestMappingInfo(this.name, patterns,
            methods, params, headers, consumes, produces, custom.getCondition());
}


org.springframework.web.servlet.mvc.method.RequestMappingInfo#getMatchingCondition

在遍历过程中,SpringMVC首先会根据@RequestMapping中的headers, params, produces, consumes, methods与实际的HttpServletRequest中的信息对比,剔除掉一些明显不合格的RequestMapping。 如果以上信息都能够匹配上,那么SpringMVC会对RequestMapping中的path进行正则匹配,剔除不合格的。

Comparator comparator = new MatchComparator(getMappingComparator(request));
Collections.sort(matches, comparator);
接下来会对所有留下来的候选@RequestMapping进行评分并排序。最后选择分数最高的那个作为结果。 评分的优先级为:

path pattern > params > headers > consumes > produces > methods
所以使用非RESTful风格的URL时,SpringMVC可以立刻找到对应的HandlerMethod来处理请求。但是当在URL中存在变量时,即使用了@PathVariable时,SpringMVC就会进行上述的复杂流程。

值得注意的是SpringMVC在匹配@RequestMapping中的path时是通过AntPathMatcher进行的,这段path匹配逻辑是从Ant中借鉴过来的。

####END

使用restful风格时,我们往往会在一个controller方法使用同一个路径,然后定义不同的httpmethod,那么问题来了,springmvc是怎么做到的呢?

首先,看下我们的Controller层代码

@SpringBootApplication
@EnableEurekaServer
@RestController
public class EurekaServerApplication {

    public static void main(String[] args) {
        SpringApplication.run(EurekaServerApplication.class, args);
    }


    @GetMapping("/hi")
    public String hi() {
        StringBuilder sb = new StringBuilder();
        sb.append("<div style=\"color:red;\">aaaaa</div>")
          .append(ESAPI.encoder().encodeForHTML("<script>alert(1)</script>"));

        String jsCode = "<div style=\"color:red;\">aaaaa</div><script>alert(1)</script>";

        String jsEncoder = ESAPI.encoder().encodeForHTML(jsCode);
        System.out.println("###########################################################");
        System.out.println(sb.toString());
        return sb.toString();
    }

    @GetMapping("/hi/{id}")
    public void getId(@PathVariable String id, String name) {
        System.out.println("hello, " + id + "name:" + name);
    }

    @PostMapping("/hi/{id}")
    public void postId(@PathVariable String id, String name) {
        System.out.println("hello, " + id + "name:" + name);
    }
}

根据路径"/hi/{id}"定义了一个get方法和post方法。

项目启动时,springmvc会扫描所有类,将加了mapping的注解的方法和url绑定,存进一个全局的mappingLookup,这里怎么匹配的就不详细介绍了。
在这里插入图片描述
createHandlerMethod 会帮我们创建一个HandlerMethod对象

	/**
	 * Create an instance from a bean instance and a method.
	 */
	public HandlerMethod(Object bean, Method method) {
		Assert.notNull(bean, "Bean is required");
		Assert.notNull(method, "Method is required");
		this.bean = bean;
		this.beanFactory = null;
		this.beanType = ClassUtils.getUserClass(bean);
		this.method = method;
		this.bridgedMethod = BridgeMethodResolver.findBridgedMethod(method);
		this.parameters = initMethodParameters();
		evaluateResponseStatus();
	}

这个对象包含了我们的方法名称 method 、方法参数 parameters 、controller对象 bean 等等
项目启动完成后,mappingLookup包含了spring扫描到的所有路径和对应的api.
这时,在浏览器访问我们的路径,http://localhost:8081/hi/2,此时springmvc拦截这个请求,在DispatcherServlet中执行doDispatch方法,
在这里插入图片描述
通过调用getHandler方法获取代理对象,继续进一步查看此方法:

在这里插入图片描述
这里会循环遍历七种mappinghandler获取最终的handler对象
这七个handler都继承了抽象类AbstractHandlerMapping,此抽象类中的方法getHandler用于获取handler 对象

	/**
	 * Look up a handler for the given request, falling back to the default
	 * handler if no specific one is found.
	 * @param request current HTTP request
	 * @return the corresponding handler instance, or the default handler
	 * @see #getHandlerInternal
	 */
	@Override
	@Nullable
	public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
		Object handler = getHandlerInternal(request);
		if (handler == null) {
			handler = getDefaultHandler();
		}
		if (handler == null) {
			return null;
		}
		// Bean name or resolved handler?
		if (handler instanceof String) {
			String handlerName = (String) handler;
			handler = obtainApplicationContext().getBean(handlerName);
		}

		HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);

		if (logger.isTraceEnabled()) {
			logger.trace("Mapped to " + handler);
		}
		else if (logger.isDebugEnabled() && !request.getDispatcherType().equals(DispatcherType.ASYNC)) {
			logger.debug("Mapped to " + executionChain.getHandler());
		}

		if (CorsUtils.isCorsRequest(request)) {
			CorsConfiguration globalConfig = this.corsConfigurationSource.getCorsConfiguration(request);
			CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
			CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
			executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
		}

		return executionChain;
	}

再看getHandlerInternal方法,不同的实现类会重写此方法,由于我们用的requestMapping注解,所以来看它的具体实现
在这里插入图片描述
先从request对象中获取我们的url访问路径,再调用lookupHandlerMethod找到对应的method对象

	/**
	 * Look up the best-matching handler method for the current request.
	 * If multiple matches are found, the best match is selected.
	 * @param lookupPath mapping lookup path within the current servlet mapping
	 * @param request the current request
	 * @return the best-matching handler method, or {@code null} if no match
	 * @see #handleMatch(Object, String, HttpServletRequest)
	 * @see #handleNoMatch(Set, String, HttpServletRequest)
	 */
	@Nullable
	protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
		List<Match> matches = new ArrayList<>();
		List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
		if (directPathMatches != null) {
			addMatchingMappings(directPathMatches, matches, request);
		}
		if (matches.isEmpty()) {
			// No choice but to go through all mappings...
			addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request);
		}

		if (!matches.isEmpty()) {
			Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
			matches.sort(comparator);
			Match bestMatch = matches.get(0);
			if (matches.size() > 1) {
				if (logger.isTraceEnabled()) {
					logger.trace(matches.size() + " matching mappings: " + matches);
				}
				if (CorsUtils.isPreFlightRequest(request)) {
					return PREFLIGHT_AMBIGUOUS_MATCH;
				}
				Match secondBestMatch = matches.get(1);
				if (comparator.compare(bestMatch, secondBestMatch) == 0) {
					Method m1 = bestMatch.handlerMethod.getMethod();
					Method m2 = secondBestMatch.handlerMethod.getMethod();
					String uri = request.getRequestURI();
					throw new IllegalStateException(
							"Ambiguous handler methods mapped for '" + uri + "': {" + m1 + ", " + m2 + "}");
				}
			}
			request.setAttribute(BEST_MATCHING_HANDLER_ATTRIBUTE, bestMatch.handlerMethod);
			handleMatch(bestMatch.mapping, lookupPath, request);
			return bestMatch.handlerMethod;
		}
		else {
			return handleNoMatch(this.mappingRegistry.getMappings().keySet(), lookupPath, request);
		}
	}

this.mappingRegistry.getMappings().keySet() 返回的就是在启动时封装的mappingLooku对象
在这里插入图片描述
继续回到上面的lookupHandlerMethod方法,调用addMatchingMappings方法找到一个最合适的matcher
在这里插入图片描述
getMatchingMapping 再继续深入这个方法,会执行getMatchingCondition方法生成一个RequestMappingInfo对象

/**
	 * Checks if all conditions in this request mapping info match the provided request and returns
	 * a potentially new request mapping info with conditions tailored to the current request.
	 * <p>For example the returned instance may contain the subset of URL patterns that match to
	 * the current request, sorted with best matching patterns on top.
	 * @return a new instance in case all conditions match; or {@code null} otherwise
	 */
	@Override
	@Nullable
	public RequestMappingInfo getMatchingCondition(HttpServletRequest request) {
		RequestMethodsRequestCondition methods = this.methodsCondition.getMatchingCondition(request);
		if (methods == null) {
			return null;
		}
		ParamsRequestCondition params = this.paramsCondition.getMatchingCondition(request);
		if (params == null) {
			return null;
		}
		HeadersRequestCondition headers = this.headersCondition.getMatchingCondition(request);
		if (headers == null) {
			return null;
		}
		ConsumesRequestCondition consumes = this.consumesCondition.getMatchingCondition(request);
		if (consumes == null) {
			return null;
		}
		ProducesRequestCondition produces = this.producesCondition.getMatchingCondition(request);
		if (produces == null) {
			return null;
		}
		PatternsRequestCondition patterns = this.patternsCondition.getMatchingCondition(request);
		if (patterns == null) {
			return null;
		}
		RequestConditionHolder custom = this.customConditionHolder.getMatchingCondition(request);
		if (custom == null) {
			return null;
		}

		return new RequestMappingInfo(this.name, patterns,
				methods, params, headers, consumes, produces, custom.getCondition());
	}

通过查看RequestMappingInfo对象的属性,能发现这个对象已经根据url找到对应的controller方法了,翻译一下这段代码的注释

/**
 * Checks if all conditions in this request mapping info match the provided request and returns
 * a potentially new request mapping info with conditions tailored to the current request.
 * <p>For example the returned instance may contain the subset of URL patterns that match to
 * the current request, sorted with best matching patterns on top.
 * @return a new instance in case all conditions match; or {@code null} otherwise
 */

/ **
*检查此请求映射信息中的所有条件是否与提供的请求匹配
并返回具有针对当前请求量身定制潜在请求映射信息

  • 例如,返回的实例可能包含与以下内容匹配的URL请求,在顶部以最佳匹配模式排序。
  • @在所有条件匹配的情况下返回新实例; 或{@code null}否则
    大概意思就是收集所有满足条件的method方法。
    在这里插入图片描述
    再拿到所有满足条件的method方法后,会对这些方法进行一个排序,然后取一个分数最高的method

在这里插入图片描述
排序实现的逻辑:

/**
	 * Compares "this" info (i.e. the current instance) with another info in the context of a request.
	 * <p>Note: It is assumed both instances have been obtained via
	 * {@link #getMatchingCondition(HttpServletRequest)} to ensure they have conditions with
	 * content relevant to current request.
	 */
	@Override
	public int compareTo(RequestMappingInfo other, HttpServletRequest request) {
		int result;
		// Automatic vs explicit HTTP HEAD mapping
		if (HttpMethod.HEAD.matches(request.getMethod())) {
			result = this.methodsCondition.compareTo(other.getMethodsCondition(), request);
			if (result != 0) {
				return result;
			}
		}
		result = this.patternsCondition.compareTo(other.getPatternsCondition(), request);
		if (result != 0) {
			return result;
		}
		result = this.paramsCondition.compareTo(other.getParamsCondition(), request);
		if (result != 0) {
			return result;
		}
		result = this.headersCondition.compareTo(other.getHeadersCondition(), request);
		if (result != 0) {
			return result;
		}
		result = this.consumesCondition.compareTo(other.getConsumesCondition(), request);
		if (result != 0) {
			return result;
		}
		result = this.producesCondition.compareTo(other.getProducesCondition(), request);
		if (result != 0) {
			return result;
		}
		// Implicit (no method) vs explicit HTTP method mappings
		result = this.methodsCondition.compareTo(other.getMethodsCondition(), request);
		if (result != 0) {
			return result;
		}
		result = this.customConditionHolder.compareTo(other.customConditionHolder, request);
		if (result != 0) {
			return result;
		}
		return 0;
	}

拿到HandlerAdapter对象后会在doDispatch方法中调用handle方法进行参数的初始化和方法的调用。
在这里插入图片描述

	/**
	 * This implementation expects the handler to be an {@link HandlerMethod}.
	 */
	@Override
	@Nullable
	public final ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
			throws Exception {

		return handleInternal(request, response, (HandlerMethod) handler);
	}

invokeHandlerMethod 调用此方法返回modelandView对象
在这里插入图片描述
再次进入invokeHandlerMethod方法,最终会调用invocableMethod.invokeAndHandle(webRequest, mavContainer);

	@Nullable
	protected ModelAndView invokeHandlerMethod(HttpServletRequest request,
			HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {

		ServletWebRequest webRequest = new ServletWebRequest(request, response);
		try {
			WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod);
			ModelFactory modelFactory = getModelFactory(handlerMethod, binderFactory);

			ServletInvocableHandlerMethod invocableMethod = createInvocableHandlerMethod(handlerMethod);
			if (this.argumentResolvers != null) {
				invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
			}
			if (this.returnValueHandlers != null) {
				invocableMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers);
			}
			invocableMethod.setDataBinderFactory(binderFactory);
			invocableMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer);

			ModelAndViewContainer mavContainer = new ModelAndViewContainer();
			mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request));
			modelFactory.initModel(webRequest, mavContainer, invocableMethod);
			mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect);

			AsyncWebRequest asyncWebRequest = WebAsyncUtils.createAsyncWebRequest(request, response);
			asyncWebRequest.setTimeout(this.asyncRequestTimeout);

			WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
			asyncManager.setTaskExecutor(this.taskExecutor);
			asyncManager.setAsyncWebRequest(asyncWebRequest);
			asyncManager.registerCallableInterceptors(this.callableInterceptors);
			asyncManager.registerDeferredResultInterceptors(this.deferredResultInterceptors);

			if (asyncManager.hasConcurrentResult()) {
				Object result = asyncManager.getConcurrentResult();
				mavContainer = (ModelAndViewContainer) asyncManager.getConcurrentResultContext()[0];
				asyncManager.clearConcurrentResult();
				LogFormatUtils.traceDebug(logger, traceOn -> {
					String formatted = LogFormatUtils.formatValue(result, !traceOn);
					return "Resume with async result [" + formatted + "]";
				});
				invocableMethod = invocableMethod.wrapConcurrentResult(result);
			}

			invocableMethod.invokeAndHandle(webRequest, mavContainer);
			if (asyncManager.isConcurrentHandlingStarted()) {
				return null;
			}

			return getModelAndView(mavContainer, modelFactory, webRequest);
		}
		finally {
			webRequest.requestCompleted();
		}
	}

invokeAndHandle方法中会执行invokeForRequest方法,在此方法中需关注
getMethodArgumentValues方法
在这里插入图片描述
getMethodArgumentValues会将request中的参数封装进行初始化
在这里插入图片描述

resolveArgument方法:

	@Override
	@Nullable
	public final Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
			NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {

		NamedValueInfo namedValueInfo = getNamedValueInfo(parameter);
		MethodParameter nestedParameter = parameter.nestedIfOptional();

		Object resolvedName = resolveStringValue(namedValueInfo.name);
		if (resolvedName == null) {
			throw new IllegalArgumentException(
					"Specified name must not resolve to null: [" + namedValueInfo.name + "]");
		}

		Object arg = resolveName(resolvedName.toString(), nestedParameter, webRequest);
		if (arg == null) {
			if (namedValueInfo.defaultValue != null) {
				arg = resolveStringValue(namedValueInfo.defaultValue);
			}
			else if (namedValueInfo.required && !nestedParameter.isOptional()) {
				handleMissingValue(namedValueInfo.name, nestedParameter, webRequest);
			}
			arg = handleNullValue(namedValueInfo.name, arg, nestedParameter.getNestedParameterType());
		}
		else if ("".equals(arg) && namedValueInfo.defaultValue != null) {
			arg = resolveStringValue(namedValueInfo.defaultValue);
		}

		if (binderFactory != null) {
			WebDataBinder binder = binderFactory.createBinder(webRequest, null, namedValueInfo.name);
			try {
				arg = binder.convertIfNecessary(arg, parameter.getParameterType(), parameter);
			}
			catch (ConversionNotSupportedException ex) {
				throw new MethodArgumentConversionNotSupportedException(arg, ex.getRequiredType(),
						namedValueInfo.name, parameter, ex.getCause());
			}
			catch (TypeMismatchException ex) {
				throw new MethodArgumentTypeMismatchException(arg, ex.getRequiredType(),
						namedValueInfo.name, parameter, ex.getCause());

			}
		}

		handleResolvedValue(arg, namedValueInfo.name, parameter, mavContainer, webRequest);

		return arg;
	}

handleResolvedValue方法会将获取的值赋值给正确的参数,至此,参数的封装就完成了,在通过doInvoke动态调用api方法。

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