SpringMVC的http请求的参数解析HandlerMethodArgumentResolver流程
文章目录
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SpringMVC的http请求的参数解析HandlerMethodArgumentResolver流程
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本文分析的HandlerMethodArgumentResolver
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初始化解析映射关系
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处理请求
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总结
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本文分析的HandlerMethodArgumentResolver
初始化解析映射关系
得到请求 url 与 RequestMappingInfo 的映射关系到 urlLookup 中；设置 RequestMappingInfo 与 HandlerMethod 的映射关系到 mappingLookup 中。得到 url -> HandlerMethod 的映射关系。
详见
RequestMappingHandlerMapping的初始化
处理请求
调用DispatcherServlet#doService->DispatcherServlet#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 {
// processedRequest是经过checkMultipart方法处理过的request请求,
// 如果不满足multipart条件，直接返回request,也就是request没有做任何处理,
// 如果满足multipart基本条件将multipartRequest转换为StandardMultipartHttpServletRequest请求。
processedRequest = checkMultipart(request);
multipartRequestParsed = (processedRequest != request);
// Determine handler for the current request.
// DispatcherServlet.getHandler方法会在底层调用HandlerMapping.getHandler方法
// 这个方法中会遍 历DispatcherServlet中的private List<HandlerMapping>
// handlerMappings链表，找到能够处理当前 request请求的第一个HandlerMapping实例并返回：
// DispatcherServlet接收到请求后，HandlerMapping将会把请求封装为HandlerExecutionChain，
// 而HandlerExecutionChain包含请求的所有信息，包括拦截器、Handler处理器等。
// HandlerExecutionChain为真正的Handler对象与Interceptor的组合类
mappedHandler = getHandler(processedRequest);
if (mappedHandler == null) {
// 如果没有找到对应的handler则抛出异常。
noHandlerFound(processedRequest, response);
return;
}
// Determine handler adapter for the current request.
// 通过getHandlerAdapter方法找到handler对应的HandlerAdapter
// 则是遍历HandlerAdpaters，然后返回第一个支持handler的Adpater.
// SimpleControllerHandlerAdapter是用来适配SimpleUrlHandlerMapping和BeanNameUrlHandlerMapping的映射的，也就是实现Controller接口的Handler。
// RequestMappingHandlerAdapter是用来适配RequestMappingHandlerMapping，也就是我们常用的RequestMapping注解。
// HttpRequestHandlerAdapter是用来适配远程调用的。
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 (logger.isDebugEnabled()) {
logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);
}
if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
return;
}
}
// 如果有拦截器，执行拦截器preHandler方法
// 如果拦截器preHandle返回false，那么请求终止。
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
// Actually invoke the handler.
// todo HandlerAdapter执行handle方法处理请求，返回ModelAndView
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
if (asyncManager.isConcurrentHandlingStarted()) {
return;
}
// 如果返回的ModelAndView不为null，并且没有设置view的话，这设置默认的view
applyDefaultViewName(processedRequest, mv);
// 如果有拦截器，执行拦截器postHandle方法
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);
}
// 然后调用processDispatchResult方法处理请求结果，封装到response中
// DispatcherServlet会将ModelAndView对象传入View层进行渲染
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);
}
}
}
}
public final ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
throws Exception {
return handleInternal(request, response, (HandlerMethod) handler);
}
protected ModelAndView handleInternal(HttpServletRequest request,
HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {
ModelAndView mav;
checkRequest(request);
// Execute invokeHandlerMethod in synchronized block if required.
// 判断当前是否需要支持在同一个session中只能线性地处理请求
if (this.synchronizeOnSession) {
// 获取当前请求的session对象
HttpSession session = request.getSession(false);
if (session != null) {
// 为当前session生成一个唯一的可以用于锁定的key
Object mutex = WebUtils.getSessionMutex(session);
synchronized (mutex) {
// 对HandlerMethod进行参数等的适配处理，并调用目标handler
mav = invokeHandlerMethod(request, response, handlerMethod);
}
}
else {
// No HttpSession available -> no mutex necessary
// 如果当前不存在session，则直接对HandlerMethod进行适配
mav = invokeHandlerMethod(request, response, handlerMethod);
}
}
else {
// No synchronization on session demanded at all...
// 如果当前不需要对session进行同步处理，则直接对HandlerMethod进行适配
mav = invokeHandlerMethod(request, response, handlerMethod);
}
...
return mav;
}
之后调invocableMethod.invokeAndHandle(webRequest, mavContainer);
protected ModelAndView invokeHandlerMethod(HttpServletRequest request,
HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {
ServletWebRequest webRequest = new ServletWebRequest(request, response);
try {
// 使用initBinderAdviceCache对@initBinder进行处理
// 获取容器中全局配置的InitBinder和当前HandlerMethod所对应的Controller中
// 配置的InitBinder，用于进行参数的绑定
WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod);
// 使用modelAttributeAdviceCache对@ModelAttribute进行处理
// 获取容器中全局配置的ModelAttribute和当前当前HandlerMethod所对应的Controller
// 中配置的ModelAttribute，这些配置的方法将会在目标方法调用之前进行调用
ModelFactory modelFactory = getModelFactory(handlerMethod, binderFactory);
// 将handlerMethod封装为一个ServletInvocableHandlerMethod对象，
// 该对象用于对当前request的整体调用流程进行了封装
ServletInvocableHandlerMethod invocableMethod = createInvocableHandlerMethod(handlerMethod);
if (this.argumentResolvers != null) {
// 设置当前容器中配置的所有ArgumentResolver
invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
}
if (this.returnValueHandlers != null) {
// 设置当前容器中配置的所有ReturnValueHandler
invocableMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers);
}
// 将前面创建的WebDataBinderFactory设置到ServletInvocableHandlerMethod中
invocableMethod.setDataBinderFactory(binderFactory);
// 设置ParameterNameDiscoverer，该对象将按照一定的规则获取当前参数的名称
invocableMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer);
ModelAndViewContainer mavContainer = new ModelAndViewContainer();
mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request));
// 这里initModel()方法主要作用是调用前面获取到的@ModelAttribute标注的方法，
// 从而达到@ModelAttribute标注的方法能够在目标Handler调用之前调用的目的
modelFactory.initModel(webRequest, mavContainer, invocableMethod);
// 获取当前的AsyncWebRequest，这里AsyncWebRequest的主要作用是用于判断目标
// handler的返回值是否为WebAsyncTask或DefferredResult，如果是这两种中的一种，
// 则说明当前请求的处理应该是异步的。所谓的异步，指的是当前请求会将Controller中
// 封装的业务逻辑放到一个线程池中进行调用，待该调用有返回结果之后再返回到response中。
// 这种处理的优点在于用于请求分发的线程能够解放出来，从而处理更多的请求，只有待目标任务
// 完成之后才会回来将该异步任务的结果返回。
mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect);
// 封装异步任务的线程池，request和interceptors到WebAsyncManager中
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);
// 这里就是用于判断当前请求是否有异步任务结果的，如果存在，则对异步任务结果进行封装
if (asyncManager.hasConcurrentResult()) {
Object result = asyncManager.getConcurrentResult();
mavContainer = (ModelAndViewContainer) asyncManager.getConcurrentResultContext()[0];
asyncManager.clearConcurrentResult();
if (logger.isDebugEnabled()) {
logger.debug("Found concurrent result value [" + result + "]");
}
// 封装异步任务的处理结果，虽然封装的是一个HandlerMethod，但只是Spring简单的封装
// 的一个Callable对象，该对象中直接将调用结果返回了。这样封装的目的在于能够统一的
// 进行右面的ServletInvocableHandlerMethod.invokeAndHandle()方法的调用
invocableMethod = invocableMethod.wrapConcurrentResult(result);
}
// 完成过程调用
// 对请求参数进行处理，调用目标HandlerMethod，并且将返回值封装为一个ModelAndView对象
invocableMethod.invokeAndHandle(webRequest, mavContainer);
if (asyncManager.isConcurrentHandlingStarted()) {
return null;
}
//2 包装ModelAndView
// 对封装的ModelAndView进行处理，主要是判断当前请求是否进行了重定向，如果进行了重定向，
// 还会判断是否需要将FlashAttributes封装到新的请求中
return getModelAndView(mavContainer, modelFactory, webRequest);
}
finally {
// 调用request destruction callbacks和对SessionAttributes进行处理
webRequest.requestCompleted();
}
}
之后调用@ModelAttribute标注的方法
public void initModel(NativeWebRequest request, ModelAndViewContainer container, HandlerMethod handlerMethod)
throws Exception {
// 在当前request中获取使用@SessionAttribute注解声明的参数
Map<String, ?> sessionAttributes = this.sessionAttributesHandler.retrieveAttributes(request);
// 将@SessionAttribute声明的参数封装到ModelAndViewContainer中
container.mergeAttributes(sessionAttributes);
// 调用前面获取的使用@ModelAttribute标注的方法
invokeModelAttributeMethods(request, container);
// 这里首先获取目标handler执行所需的参数中与@SessionAttribute同名或同类型的参数，
// 也就是handler想要直接从@SessionAttribute中声明的参数中获取的参数。然后对这些参数
// 进行遍历，首先判断request中是否包含该属性，如果不包含，则从之前的SessionAttribute缓存
// 中获取，如果两个都没有，则直接抛出异常
for (String name : findSessionAttributeArguments(handlerMethod)) {
if (!container.containsAttribute(name)) {
Object value = this.sessionAttributesHandler.retrieveAttribute(request, name);
if (value == null) {
throw new HttpSessionRequiredException("Expected session attribute '" + name + "'", name);
}
container.addAttribute(name, value);
}
}
}
private void invokeModelAttributeMethods(NativeWebRequest request, ModelAndViewContainer container)
throws Exception {
while (!this.modelMethods.isEmpty()) {
// 这里getNextModelMethod()方法始终会获取modelMethods中的第0号为的方法，
// 后续该方法执行完了之后则会将该方法从modelMethods移除掉，因而这里while
// 循环只需要判断modelMethods是否为空即可
InvocableHandlerMethod modelMethod = getNextModelMethod(container).getHandlerMethod();
// 获取当前方法中标注的ModelAttribute属性，然后判断当前request中是否有与该属性中name字段
// 标注的值相同的属性，如果存在，并且当前ModelAttribute设置了不对该属性进行绑定，那么
// 就直接略过当前方法的执行
ModelAttribute ann = modelMethod.getMethodAnnotation(ModelAttribute.class);
Assert.state(ann != null, "No ModelAttribute annotation");
if (container.containsAttribute(ann.name())) {
if (!ann.binding()) {
container.setBindingDisabled(ann.name());
}
continue;
}
// 通过ArgumentResolver对方法参数进行处理，并且调用目标方法
Object returnValue = modelMethod.invokeForRequest(request, container);
// 如果当前方法的返回值不为空，则判断当前@ModelAttribute是否设置了需要绑定返回值，
// 如果设置了，则将返回值绑定到请求中，后续handler可以直接使用该参数
if (!modelMethod.isVoid()){
String returnValueName = getNameForReturnValue(returnValue, modelMethod.getReturnType());
if (!ann.binding()) {
container.setBindingDisabled(returnValueName);
}
// 如果request中不包含该参数，则将该返回值添加到ModelAndViewContainer中，
// 供handler使用
if (!container.containsAttribute(returnValueName)) {
container.addAttribute(returnValueName, returnValue);
}
}
}
}
public Object invokeForRequest(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
Object... providedArgs) throws Exception {
// 处理方法的参数值
if (logger.isDebugEnabled()) {
logger.debug("使用HandlerMethodArgumentResolver来处理方法的参数值");
}
Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);
if (logger.isTraceEnabled()) {
logger.trace("Invoking '" + ClassUtils.getQualifiedMethodName(getMethod(), getBeanType()) +
"' with arguments " + Arrays.toString(args));
}
// 这里doInvoke()方法主要是结合处理后的参数，使用反射对目标方法进行调用
Object returnValue = doInvoke(args);
if (logger.isTraceEnabled()) {
logger.trace("Method [" + ClassUtils.getQualifiedMethodName(getMethod(), getBeanType()) +
"] returned [" + returnValue + "]");
}
return returnValue;
}
反射调用@ModelAttribute标注的方法
protected Object doInvoke(Object... args) throws Exception {
ReflectionUtils.makeAccessible(getBridgedMethod());
try {
return getBridgedMethod().invoke(getBean(), args);
}
catch (IllegalArgumentException ex) {
assertTargetBean(getBridgedMethod(), getBean(), args);
String text = (ex.getMessage() != null ? ex.getMessage() : "Illegal argument");
throw new IllegalStateException(getInvocationErrorMessage(text, args), ex);
}
catch (InvocationTargetException ex) {
// Unwrap for HandlerExceptionResolvers ...
Throwable targetException = ex.getTargetException();
if (targetException instanceof RuntimeException) {
throw (RuntimeException) targetException;
}
else if (targetException instanceof Error) {
throw (Error) targetException;
}
else if (targetException instanceof Exception) {
throw (Exception) targetException;
}
else {
String text = getInvocationErrorMessage("Failed to invoke handler method", args);
throw new IllegalStateException(text, targetException);
}
}
}
解析请求参数
本次解析Model参数，@RequestBody标注参数，@RequestParam标注参数，@PathVariable标注参数，以及普通入参
在Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);里面解析请求参数
private Object[] getMethodArgumentValues(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
Object... providedArgs) throws Exception {
// 获取当前handler所声明的所有参数，主要包括参数名，参数类型，参数位置，所标注的注解等等属性
MethodParameter[] parameters = getMethodParameters();
Object[] args = new Object[parameters.length];
for (int i = 0; i < parameters.length; i++) {
MethodParameter parameter = parameters[i];
parameter.initParameterNameDiscovery(this.parameterNameDiscoverer);
// providedArgs是调用方提供的参数，这里主要是判断这些参数中是否有当前类型
// 或其子类型的参数，如果有，则直接使用调用方提供的参数，对于请求处理而言，默认情况下，
// 调用方提供的参数都是长度为0的数组
args[i] = resolveProvidedArgument(parameter, providedArgs);
if (args[i] != null) {
continue;
}
// 如果在调用方提供的参数中不能找到当前类型的参数值，则遍历Spring容器中所有的
// ArgumentResolver，判断哪种类型的Resolver支持对当前参数的解析，这里的判断
// 方式比较简单，比如RequestParamMethodArgumentResolver就是判断当前参数
// 是否使用@RequestParam注解进行了标注
if (this.argumentResolvers.supportsParameter(parameter)) {
try {
// 如果能够找到对当前参数进行处理的ArgumentResolver，则调用其
// resolveArgument()方法从request中获取对应的参数值，并且进行转换
args[i] = this.argumentResolvers.resolveArgument(
parameter, mavContainer, request, this.dataBinderFactory);
if (logger.isDebugEnabled()) {
logger.debug("处理后参数值："+args[i]);
}
continue;
}
catch (Exception ex) {
if (logger.isDebugEnabled()) {
logger.debug(getArgumentResolutionErrorMessage("Failed to resolve", i), ex);
}
throw ex;
}
}
// 如果进行了参数处理之后当前参数还是为空，则抛出异常
if (args[i] == null) {
throw new IllegalStateException("Could not resolve method parameter at index " +
parameter.getParameterIndex() + " in " + parameter.getExecutable().toGenericString() +
": " + getArgumentResolutionErrorMessage("No suitable resolver for", i));
}
}
return args;
}
public boolean supportsParameter(MethodParameter parameter) {
return getArgumentResolver(parameter) != null;
}
private HandlerMethodArgumentResolver getArgumentResolver(MethodParameter parameter) {
HandlerMethodArgumentResolver result = this.argumentResolverCache.get(parameter);
if (result == null) {
for (HandlerMethodArgumentResolver resolver : this.argumentResolvers) {
if (resolver.supportsParameter(parameter)) {
result = resolver;
this.argumentResolverCache.put(parameter, result);
break;
}
}
}
return result;
}
Model参数解析器是：ModelMethodProcessor
判断是否能解析
public boolean supportsParameter(MethodParameter parameter) {
return Model.class.isAssignableFrom(parameter.getParameterType());
}
处理参数
public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
Assert.state(mavContainer != null, "ModelAndViewContainer is required for model exposure");
return mavContainer.getModel();
}
@RequestBody标注参数的参数解析器是：RequestResponseBodyMethodProcessor
前提是：必须要引入json解析相关的类，
例如：1.fastjson需要引入com.alibaba.fastjson并添加HttpMessageConverter
@Override
protected void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
converters.clear();
converters.add(stringHttpMessageConverter());
converters.add(fastJsonHttpMessageConverter());
}
@Bean
public FastJsonHttpMessageConverter fastJsonHttpMessageConverter() {
FastJsonHttpMessageConverter fastJsonHttpMessageConverter = new FastJsonHttpMessageConverter();
FastJsonConfig fastJsonConfig = new FastJsonConfig();
fastJsonConfig.setSerializerFeatures(
SerializerFeature.QuoteFieldNames,
SerializerFeature.WriteMapNullValue,//保留空的字段
SerializerFeature.WriteNullListAsEmpty,//List null-> []
SerializerFeature.WriteDateUseDateFormat,// 日期格式化
SerializerFeature.WriteNullStringAsEmpty);//String null -> ""
List<MediaType> mediaTypeList = new ArrayList<>();
mediaTypeList.add(MediaType.APPLICATION_JSON_UTF8);
mediaTypeList.add(MediaType.APPLICATION_JSON);
fastJsonHttpMessageConverter.setSupportedMediaTypes(mediaTypeList);
fastJsonHttpMessageConverter.setFastJsonConfig(fastJsonConfig);
return fastJsonHttpMessageConverter;
}
/**
* 在ResponseBody注解下，Spring处理返回值为String时会用到StringHttpMessageConverter
*
*/
@Bean
public StringHttpMessageConverter stringHttpMessageConverter() {
StringHttpMessageConverter httpMessageConverter = new StringHttpMessageConverter();
httpMessageConverter.setDefaultCharset(Charset.forName("UTF-8"));
return httpMessageConverter;
}
2.如果使用jackson需要pom引入：com.fasterxml.jackson.core.jackson-databind
下面以fastjson为例进行解析
判断是否能解析
public boolean supportsParameter(MethodParameter parameter) {
return parameter.hasParameterAnnotation(RequestBody.class);
}
处理参数
public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
parameter = parameter.nestedIfOptional();
// 使用 HttpMessageConverter 将 请求body 中数据解析出来
Object arg = readWithMessageConverters(webRequest, parameter, parameter.getNestedGenericParameterType());
String name = Conventions.getVariableNameForParameter(parameter);
if (binderFactory != null) {
WebDataBinder binder = binderFactory.createBinder(webRequest, arg, name);
if (arg != null) {
validateIfApplicable(binder, parameter);
if (binder.getBindingResult().hasErrors() && isBindExceptionRequired(binder, parameter)) {
throw new MethodArgumentNotValidException(parameter, binder.getBindingResult());
}
}
if (mavContainer != null) {
mavContainer.addAttribute(BindingResult.MODEL_KEY_PREFIX + name, binder.getBindingResult());
}
}
return adaptArgumentIfNecessary(arg, parameter);
}
protected <T> Object readWithMessageConverters(NativeWebRequest webRequest, MethodParameter parameter,
Type paramType) throws IOException, HttpMediaTypeNotSupportedException, HttpMessageNotReadableException {
HttpServletRequest servletRequest = webRequest.getNativeRequest(HttpServletRequest.class);
Assert.state(servletRequest != null, "No HttpServletRequest");
ServletServerHttpRequest inputMessage = new ServletServerHttpRequest(servletRequest);
// 使用 HttpMessageConverter 将 请求body 中数据解析出来
Object arg = readWithMessageConverters(inputMessage, parameter, paramType);
if (arg == null && checkRequired(parameter)) {
throw new HttpMessageNotReadableException("Required request body is missing: " +
parameter.getExecutable().toGenericString());
}
return arg;
}
protected <T> Object readWithMessageConverters(HttpInputMessage inputMessage, MethodParameter parameter,
Type targetType) throws IOException, HttpMediaTypeNotSupportedException, HttpMessageNotReadableException {
MediaType contentType;
boolean noContentType = false;
try {
// 获取 ContentType
contentType = inputMessage.getHeaders().getContentType();
}
catch (InvalidMediaTypeException ex) {
throw new HttpMediaTypeNotSupportedException(ex.getMessage());
}
if (contentType == null) {
noContentType = true;
contentType = MediaType.APPLICATION_OCTET_STREAM;
}
Class<?> contextClass = parameter.getContainingClass();
// 获取 method 的参数的类型
Class<T> targetClass = (targetType instanceof Class ? (Class<T>) targetType : null);
if (targetClass == null) {
ResolvableType resolvableType = ResolvableType.forMethodParameter(parameter);
targetClass = (Class<T>) resolvableType.resolve();
}
HttpMethod httpMethod = (inputMessage instanceof HttpRequest ? ((HttpRequest) inputMessage).getMethod() : null);
Object body = NO_VALUE;
EmptyBodyCheckingHttpInputMessage message;
try {
message = new EmptyBodyCheckingHttpInputMessage(inputMessage);
// 使用一个 HttpMessageConverter 将 请求body 中数据解析出来
for (HttpMessageConverter<?> converter : this.messageConverters) {
Class<HttpMessageConverter<?>> converterType = (Class<HttpMessageConverter<?>>) converter.getClass();
GenericHttpMessageConverter<?> genericConverter =
(converter instanceof GenericHttpMessageConverter ? (GenericHttpMessageConverter<?>) converter : null);
// 选出一个 HttpMessageConverter
if (genericConverter != null ? genericConverter.canRead(targetType, contextClass, contentType) :
(targetClass != null && converter.canRead(targetClass, contentType))) {
if (logger.isDebugEnabled()) {
logger.debug("Read [" + targetType + "] as \"" + contentType + "\" with [" + converter + "]");
}
// 使用 HttpMessageConverter 解析数据
if (message.hasBody()) {
HttpInputMessage msgToUse =
getAdvice().beforeBodyRead(message, parameter, targetType, converterType);
body = (genericConverter != null ? genericConverter.read(targetType, contextClass, msgToUse) :
((HttpMessageConverter<T>) converter).read(targetClass, msgToUse));
body = getAdvice().afterBodyRead(body, msgToUse, parameter, targetType, converterType);
}
else {
body = getAdvice().handleEmptyBody(null, message, parameter, targetType, converterType);
}
break;
}
}
}
catch (IOException ex) {
throw new HttpMessageNotReadableException("I/O error while reading input message", ex);
}
if (body == NO_VALUE) {
if (httpMethod == null || !SUPPORTED_METHODS.contains(httpMethod) ||
(noContentType && !message.hasBody())) {
return null;
}
throw new HttpMediaTypeNotSupportedException(contentType, this.allSupportedMediaTypes);
}
return body;
}
public boolean canRead(Class<?> clazz, @Nullable MediaType mediaType) {
return supports(clazz) && canRead(mediaType);
}
FastJsonHttpMessageConverter的supports方法：
protected boolean supports(Class<?> clazz) {
return true;
}
FastJsonHttpMessageConverter支持两种类型的MediaType：application/json;charset=UTF-8, application/json
protected boolean canRead(@Nullable MediaType mediaType) {
if (mediaType == null) {
return true;
}
for (MediaType supportedMediaType : getSupportedMediaTypes()) {
if (supportedMediaType.includes(mediaType)) {
return true;
}
}
return false;
}
使用FastJsonHttpMessageConverter读取数据并反序列化成对象
public Object read(Type type, //
Class<?> contextClass, //
HttpInputMessage inputMessage //
) throws IOException, HttpMessageNotReadableException {
return readType(getType(type, contextClass), inputMessage);
}
private Object readType(Type type, HttpInputMessage inputMessage) {
try {
InputStream in = inputMessage.getBody();
return JSON.parseObject(in,
fastJsonConfig.getCharset(),
type,
fastJsonConfig.getParserConfig(),
fastJsonConfig.getParseProcess(),
JSON.DEFAULT_PARSER_FEATURE,
fastJsonConfig.getFeatures());
} catch (JSONException ex) {
throw new HttpMessageNotReadableException("JSON parse error: " + ex.getMessage(), ex);
} catch (IOException ex) {
throw new HttpMessageNotReadableException("I/O error while reading input message", ex);
}
}
StringHttpMessageConverter的supports方法：
@Override
public boolean supports(Class<?> clazz) {
return String.class == clazz;
}
StringHttpMessageConverter支持的MediaType是MediaType.ALL，所以String类型且加@RequestBody标注的参数的都能处理。
使用StringHttpMessageConverter读取数据
public final T read(Class<? extends T> clazz, HttpInputMessage inputMessage)
throws IOException, HttpMessageNotReadableException {
return readInternal(clazz, inputMessage);
}
protected String readInternal(Class<? extends String> clazz, HttpInputMessage inputMessage) throws IOException {
Charset charset = getContentTypeCharset(inputMessage.getHeaders().getContentType());
return StreamUtils.copyToString(inputMessage.getBody(), charset);
}
@RequestParam标注参数以及没有注解的简单参数的参数解析器是：RequestParamMethodArgumentResolver
判断是否能解析
public boolean supportsParameter(MethodParameter parameter) {
// 有 @RequestParam 注解
if (parameter.hasParameterAnnotation(RequestParam.class)) {
if (Map.class.isAssignableFrom(parameter.nestedIfOptional().getNestedParameterType())) {
RequestParam requestParam = parameter.getParameterAnnotation(RequestParam.class);
return (requestParam != null && StringUtils.hasText(requestParam.name()));
}
else {
return true;
}
}
else {
if (parameter.hasParameterAnnotation(RequestPart.class)) {
return false;
}
parameter = parameter.nestedIfOptional();
if (MultipartResolutionDelegate.isMultipartArgument(parameter)) {
return true;
}
else if (this.useDefaultResolution) {
// 是简单参数
return BeanUtils.isSimpleProperty(parameter.getNestedParameterType());
}
else {
return false;
}
}
}
处理参数
org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver#resolveArgument
public final Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
// 底层使用 asm 来获取方法中的参数的名称
NamedValueInfo namedValueInfo = getNamedValueInfo(parameter);
MethodParameter nestedParameter = parameter.nestedIfOptional();
// 获取方法的参数名称
Object resolvedName = resolveStringValue(namedValueInfo.name);
if (resolvedName == null) {
throw new IllegalArgumentException(
"Specified name must not resolve to null: [" + namedValueInfo.name + "]");
}
// 根据方法的参数名称获取 http请求的参数值
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) {
// 创建 WebDataBinder，并调用 @InitBinder 标注的方法
WebDataBinder binder = binderFactory.createBinder(webRequest, null, namedValueInfo.name);
try {
// 使用 SimpleTypeConverter 转换，其中 conversionService 都是从 RequestMappingHandlerAdapter 中获取
// conversionService 中含有大量默认的 Converter
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;
}
调用AbstractNamedValueMethodArgumentResolver#resolveStringValue 来解析参数名
private Object resolveStringValue(String value) {
if (this.configurableBeanFactory == null) {
return value;
}
// ${} 解析处理
String placeholdersResolved = this.configurableBeanFactory.resolveEmbeddedValue(value);
BeanExpressionResolver exprResolver = this.configurableBeanFactory.getBeanExpressionResolver();
if (exprResolver == null || this.expressionContext == null) {
return value;
}
// #{} 解析处理
return exprResolver.evaluate(placeholdersResolved, this.expressionContext);
}
org.springframework.web.bind.support.DefaultDataBinderFactory#createBinder创建 WebDataBinder，并调用 @InitBinder 标注的方法，在这个方法里面通常registerCustomEditor来注册用户自定义的转换器提供string->指定类的能力
public final WebDataBinder createBinder(
NativeWebRequest webRequest, @Nullable Object target, String objectName) throws Exception {
WebDataBinder dataBinder = createBinderInstance(target, objectName, webRequest);
if (this.initializer != null) {
// 初始化 WebDataBinder, 设置一些重要属性
this.initializer.initBinder(dataBinder, webRequest);
}
// 调用 @InitBinder 标注的方法
initBinder(dataBinder, webRequest);
return dataBinder;
}
org.springframework.validation.DataBinder#convertIfNecessary(java.lang.Object, java.lang.Class, org.springframework.core.MethodParameter)
public <T> T convertIfNecessary(@Nullable Object value, @Nullable Class<T> requiredType,
@Nullable MethodParameter methodParam) throws TypeMismatchException {
// 使用 SimpleTypeConverter 转换，其中 conversionService 都是从 RequestMappingHandlerAdapter 中获取
// conversionService 中含有大量默认的 Converter
return getTypeConverter().convertIfNecessary(value, requiredType, methodParam);
}
public <T> T convertIfNecessary(@Nullable Object value, @Nullable Class<T> requiredType, @Nullable MethodParameter methodParam)
throws TypeMismatchException {
return doConvert(value, requiredType, methodParam, null);
}
调用org.springframework.beans.TypeConverterSupport#doConvert来进行参数转换，支持用户自定义的转换器以及内置的Converter
private <T> T doConvert(@Nullable Object value,@Nullable Class<T> requiredType,
@Nullable MethodParameter methodParam, @Nullable Field field) throws TypeMismatchException {
Assert.state(this.typeConverterDelegate != null, "No TypeConverterDelegate");
try {
if (field != null) {
return this.typeConverterDelegate.convertIfNecessary(value, requiredType, field);
}
else {
return this.typeConverterDelegate.convertIfNecessary(value, requiredType, methodParam);
}
}
catch (ConverterNotFoundException | IllegalStateException ex) {
throw new ConversionNotSupportedException(value, requiredType, ex);
}
catch (ConversionException | IllegalArgumentException ex) {
throw new TypeMismatchException(value, requiredType, ex);
}
}
真正进行类型转换
public <T> T convertIfNecessary(@Nullable String propertyName, @Nullable Object oldValue, @Nullable Object newValue,
@Nullable Class<T> requiredType, @Nullable TypeDescriptor typeDescriptor) throws IllegalArgumentException {
// 获取客户自定义的 PropertyEditor, 在调用 @InitBinder 标注的方法的时候，在registerCustomEditor注册的用户自定义的转换器
PropertyEditor editor = this.propertyEditorRegistry.findCustomEditor(requiredType, propertyName);
ConversionFailedException conversionAttemptEx = null;
// No custom editor but custom ConversionService specified?
// conversionService 包含着所有的转换器
ConversionService conversionService = this.propertyEditorRegistry.getConversionService();
if (editor == null && conversionService != null && newValue != null && typeDescriptor != null) {
TypeDescriptor sourceTypeDesc = TypeDescriptor.forObject(newValue);
if (conversionService.canConvert(sourceTypeDesc, typeDescriptor)) {
try {
return (T) conversionService.convert(newValue, sourceTypeDesc, typeDescriptor);
}
catch (ConversionFailedException ex) {
// fallback to default conversion logic below
conversionAttemptEx = ex;
}
}
}
Object convertedValue = newValue;
// Value not of required type?
if (editor != null || (requiredType != null && !ClassUtils.isAssignableValue(requiredType, convertedValue))) {
if (typeDescriptor != null && requiredType != null && Collection.class.isAssignableFrom(requiredType) &&
convertedValue instanceof String) {
TypeDescriptor elementTypeDesc = typeDescriptor.getElementTypeDescriptor();
if (elementTypeDesc != null) {
Class<?> elementType = elementTypeDesc.getType();
if (Class.class == elementType || Enum.class.isAssignableFrom(elementType)) {
convertedValue = StringUtils.commaDelimitedListToStringArray((String) convertedValue);
}
}
}
if (editor == null) {
editor = findDefaultEditor(requiredType);
}
// 使用客户自定义的 PropertyEditor 进行转换
convertedValue = doConvertValue(oldValue, convertedValue, requiredType, editor);
}
。。。
return (T) convertedValue;
}
小结
- 调用@InitBinder 标注的方法，在这个方法里面通常registerCustomEditor来注册用户自定义的转换器提供string->指定类的能力
- 绑定http请求参数到入参参数（简单参数）中，支持类型转换
@PathVariable标注参数的参数解析器是：PathVariableMethodArgumentResolver
判断是否能解析
public boolean supportsParameter(MethodParameter parameter) {
if (!parameter.hasParameterAnnotation(PathVariable.class)) {
return false;
}
if (Map.class.isAssignableFrom(parameter.nestedIfOptional().getNestedParameterType())) {
PathVariable pathVariable = parameter.getParameterAnnotation(PathVariable.class);
return (pathVariable != null && StringUtils.hasText(pathVariable.value()));
}
return true;
}
处理参数
调用AbstractNamedValueMethodArgumentResolver#resolveArgument方法同上，之后调resolveName方法
protected Object resolveName(String name, MethodParameter parameter, NativeWebRequest request) throws Exception {
Map<String, String> uriTemplateVars = (Map<String, String>) request.getAttribute(
HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE, RequestAttributes.SCOPE_REQUEST);
return (uriTemplateVars != null ? uriTemplateVars.get(name) : null);
}
在根据路径获取 HandlerMethod 的时候设置了HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE属性，详见org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#getHandlerInternal方法
小结
- 调用@InitBinder 标注的方法，在这个方法里面通常registerCustomEditor来注册用户自定义的转换器提供string->指定类的能力
- 绑定http请求参数到入参参数（简单参数）中，支持类型转换
处理复杂类型的参数解析器是：ServletModelAttributeMethodProcessor
判断是否能解析：只能处理复杂类型，通常是用户自定义类
public boolean supportsParameter(MethodParameter parameter) {
return (parameter.hasParameterAnnotation(ModelAttribute.class) ||
(this.annotationNotRequired && !BeanUtils.isSimpleProperty(parameter.getParameterType())));
}
处理参数
public final Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
Assert.state(mavContainer != null, "ModelAttributeMethodProcessor requires ModelAndViewContainer");
Assert.state(binderFactory != null, "ModelAttributeMethodProcessor requires WebDataBinderFactory");
// 根据@ModelAttribute参数注释（如果存在）
// 或根据方法参数的 简单类名，第一个字母小写
String name = ModelFactory.getNameForParameter(parameter);
ModelAttribute ann = parameter.getParameterAnnotation(ModelAttribute.class);
if (ann != null) {
mavContainer.setBinding(name, ann.binding());
}
Object attribute = null;
BindingResult bindingResult = null;
// 从mavContainer.getModel() 中获取 方法参数简单名称，即要写入参数中的属性
if (mavContainer.containsAttribute(name)) {
attribute = mavContainer.getModel().get(name);
}
else {
// 反射创建方法入参中的类
try {
attribute = createAttribute(name, parameter, binderFactory, webRequest);
}
catch (BindException ex) {
if (isBindExceptionRequired(parameter)) {
// No BindingResult parameter -> fail with BindException
throw ex;
}
// Otherwise, expose null/empty value and associated BindingResult
if (parameter.getParameterType() == Optional.class) {
attribute = Optional.empty();
}
bindingResult = ex.getBindingResult();
}
}
if (bindingResult == null) {
// Bean property binding and validation;
// skipped in case of binding failure on construction.
// 创建 WebDataBinder，并调用 @InitBinder 标注的方法
WebDataBinder binder = binderFactory.createBinder(webRequest, attribute, name);
if (binder.getTarget() != null) {
if (!mavContainer.isBindingDisabled(name)) {
// 将请求绑定至目标binder的target对象，也就是刚刚创建的attribute对象。
bindRequestParameters(binder, webRequest);
}
// 如果有验证，则验证参数
validateIfApplicable(binder, parameter);
if (binder.getBindingResult().hasErrors() && isBindExceptionRequired(binder, parameter)) {
throw new BindException(binder.getBindingResult());
}
}
// Value type adaptation, also covering java.util.Optional
if (!parameter.getParameterType().isInstance(attribute)) {
// 使用 SimpleTypeConverter 转换，其中 conversionService 都是从 RequestMappingHandlerAdapter 中获取
// conversionService 中含有大量默认的 Converter
attribute = binder.convertIfNecessary(binder.getTarget(), parameter.getParameterType(), parameter);
}
bindingResult = binder.getBindingResult();
}
// Add resolved attribute and BindingResult at the end of the model
Map<String, Object> bindingResultModel = bindingResult.getModel();
mavContainer.removeAttributes(bindingResultModel);
mavContainer.addAllAttributes(bindingResultModel);
return attribute;
}
将请求绑定至目标binder的target对象，也就是刚刚创建的attribute对象最终调到
protected void applyPropertyValues(MutablePropertyValues mpvs) {
try {
// Bind request parameters onto target object.
getPropertyAccessor().setPropertyValues(mpvs, isIgnoreUnknownFields(), isIgnoreInvalidFields());
}
catch (PropertyBatchUpdateException ex) {
// Use bind error processor to create FieldErrors.
for (PropertyAccessException pae : ex.getPropertyAccessExceptions()) {
getBindingErrorProcessor().processPropertyAccessException(pae, getInternalBindingResult());
}
}
}
public void setPropertyValues(PropertyValues pvs, boolean ignoreUnknown, boolean ignoreInvalid)
throws BeansException {
List<PropertyAccessException> propertyAccessExceptions = null;
List<PropertyValue> propertyValues = (pvs instanceof MutablePropertyValues ?
((MutablePropertyValues) pvs).getPropertyValueList() : Arrays.asList(pvs.getPropertyValues()));
for (PropertyValue pv : propertyValues) {
try {
// This method may throw any BeansException, which won't be caught
// here, if there is a critical failure such as no matching field.
// We can attempt to deal only with less serious exceptions.
// 将请求参数中的属性赋值到方法的入参中
setPropertyValue(pv);
}
catch (NotWritablePropertyException ex) {
if (!ignoreUnknown) {
throw ex;
}
// Otherwise, just ignore it and continue...
}
catch (NullValueInNestedPathException ex) {
if (!ignoreInvalid) {
throw ex;
}
// Otherwise, just ignore it and continue...
}
catch (PropertyAccessException ex) {
if (propertyAccessExceptions == null) {
propertyAccessExceptions = new ArrayList<>();
}
propertyAccessExceptions.add(ex);
}
}
// If we encountered individual exceptions, throw the composite exception.
if (propertyAccessExceptions != null) {
PropertyAccessException[] paeArray = propertyAccessExceptions.toArray(new PropertyAccessException[0]);
throw new PropertyBatchUpdateException(paeArray);
}
}
public void setPropertyValue(PropertyValue pv) throws BeansException {
PropertyTokenHolder tokens = (PropertyTokenHolder) pv.resolvedTokens;
if (tokens == null) {
String propertyName = pv.getName();
AbstractNestablePropertyAccessor nestedPa;
try {
//根据属性名获取BeanWrapImpl对象，支持多重属性的递归分析处理
nestedPa = getPropertyAccessorForPropertyPath(propertyName);
}
catch (NotReadablePropertyException ex) {
throw new NotWritablePropertyException(getRootClass(), this.nestedPath + propertyName,
"Nested property in path '" + propertyName + "' does not exist", ex);
}
// 经过上面的递归后，获取到最终需要操作的属性的对象，下面将根据该属性对象，获取最终要操作的内嵌对象的属性，
// 生成PropertyTokenHolder，内省设置属性值
tokens = getPropertyNameTokens(getFinalPath(nestedPa, propertyName));
if (nestedPa == this) {
pv.getOriginalPropertyValue().resolvedTokens = tokens;
}
nestedPa.setPropertyValue(tokens, pv);
}
else {
setPropertyValue(tokens, pv);
}
}
递归处理比较复杂，不展开分析
小结
- 先从model中根据类的简单名称（第一个字母小写）获取入参参数类或者反射创建入参参数类
- 调用@InitBinder 标注的方法，在这个方法里面通常registerCustomEditor来注册用户自定义的转换器提供string->指定类的能力
- 绑定http请求参数到入参参数类的属性中，支持类型转换，支持递归处理
总结
类关系图：
[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-EzHq68LL-1684591466071)(assets/image-20221017204656903.png)]
- Model参数的参数解析器是：ModelMethodProcessor
- @RequestBody标注参数的参数解析器是：RequestResponseBodyMethodProcessor
-
@RequestParam标注以及没有注解的
简单参数
的参数解析器是：RequestParamMethodArgumentResolver -
@PathVariable标注参数的
简单参数
的参数解析器是：PathVariableMethodArgumentResolver -
普通入参（
非简单参数
）即兜底的参数解析器是：ServletModelAttributeMethodProcessor - 需要使用 spring 进行类型转换的都会调用@InitBinder 标注的方法
RequestParamMethodArgumentResolver和PathVariableMethodArgumentResolver都使用父类的org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver#resolveArgument方法进行参数解析。
);
}
// 经过上面的递归后，获取到最终需要操作的属性的对象，下面将根据该属性对象，获取最终要操作的内嵌对象的属性，
// 生成PropertyTokenHolder，内省设置属性值
tokens = getPropertyNameTokens(getFinalPath(nestedPa, propertyName));
if (nestedPa == this) {
pv.getOriginalPropertyValue().resolvedTokens = tokens;
}
nestedPa.setPropertyValue(tokens, pv);
}
else {
setPropertyValue(tokens, pv);
}
}
递归处理比较复杂，不展开分析
##### 小结
1. 先从model中根据类的简单名称（第一个字母小写）获取入参参数类或者反射创建入参参数类
2. 调用@InitBinder 标注的方法，在这个方法里面通常registerCustomEditor来注册用户自定义的转换器提供string->指定类的能力
3. 绑定http请求参数到入参参数类的属性中，支持类型转换，支持递归处理
## 总结
类关系图：
1. Model参数的参数解析器是：ModelMethodProcessor
2. @RequestBody标注参数的参数解析器是：RequestResponseBodyMethodProcessor
3. @RequestParam标注以及没有注解的**简单参数**的参数解析器是：RequestParamMethodArgumentResolver
4. @PathVariable标注参数的**简单参数**的参数解析器是：PathVariableMethodArgumentResolver
5. 普通入参（**非简单参数**）即兜底的参数解析器是：ServletModelAttributeMethodProcessor
6. 需要使用 spring 进行类型转换的都会调用@InitBinder 标注的方法
RequestParamMethodArgumentResolver和PathVariableMethodArgumentResolver都使用父类的org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver#resolveArgument方法进行参数解析。
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