SpringMVC-解析@RequestParam参数
InvocableHandlerMethod.invokeForRequest执行请求时会调用InvocableHandlerMethod.getMethodArgumentValues解析方法参数。
InvocableHandlerMethod.getMethodArgumentValues
protected Object[] getMethodArgumentValues(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
Object... providedArgs) throws Exception {
MethodParameter[] parameters = getMethodParameters();
if (ObjectUtils.isEmpty(parameters)) {
return EMPTY_ARGS;
}
Object[] args = new Object[parameters.length];
for (int i = 0; i < parameters.length; i++) {
MethodParameter parameter = parameters[i];
parameter.initParameterNameDiscovery(this.parameterNameDiscoverer);
args[i] = findProvidedArgument(parameter, providedArgs);
if (args[i] != null) {
continue;
}
if (!this.resolvers.supportsParameter(parameter)) {
throw new IllegalStateException(formatArgumentError(parameter, "No suitable resolver"));
}
try {
args[i] = this.resolvers.resolveArgument(parameter, mavContainer, request, this.dataBinderFactory);
}
catch (Exception ex) {
// Leave stack trace for later, exception may actually be resolved and handled...
if (logger.isDebugEnabled()) {
String exMsg = ex.getMessage();
if (exMsg != null && !exMsg.contains(parameter.getExecutable().toGenericString())) {
logger.debug(formatArgumentError(parameter, exMsg));
}
}
throw ex;
}
}
return args;
}
获取handle方法的所有参数，遍历参数，调用resolvers.supportsParameter判断方法解析器是否支持解析参数，如果支持并缓存。不支持则抛出异常。resolvers.resolveArgument解析参数。
HandlerMethodArgumentResolverComposite.supportsParameter(MethodParameter parameter)
public boolean supportsParameter(MethodParameter parameter) {
return getArgumentResolver(parameter) != null;
}
HandlerMethodArgumentResolverComposite.getArgumentResolver(MethodParameter parameter)
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;
}
遍历参数解析器，调用resolver.supportsParameter判断是否支持解析参数，如支持则加入argumentResolverCache，返回。如果没有支持解析参数的解析器则返回null。@RequestParam参数由RequestParamMethodArgumentResolver解析。
RequestParamMethodArgumentResolver.supportsParameter(MethodParameter parameter)
public boolean supportsParameter(MethodParameter parameter) {
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) {
return BeanUtils.isSimpleProperty(parameter.getNestedParameterType());
}
else {
return false;
}
}
}
如果参数有@RequestParam注解则返回true。
AbstractNamedValueMethodArgumentResolver.resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory)
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 = resolveEmbeddedValuesAndExpressions(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 = resolveEmbeddedValuesAndExpressions(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 = resolveEmbeddedValuesAndExpressions(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());
}
// Check for null value after conversion of incoming argument value
if (arg == null && namedValueInfo.defaultValue == null &&
namedValueInfo.required && !nestedParameter.isOptional()) {
handleMissingValueAfterConversion(namedValueInfo.name, nestedParameter, webRequest);
}
}
handleResolvedValue(arg, namedValueInfo.name, parameter, mavContainer, webRequest);
return arg;
}
1、getNamedValueInfo获取参数名
2、resolveEmbeddedValuesAndExpressions解析参数名，参数可能有表达式或${}
3、resolveName解析参数值
4、如果没有获取到参数值，resolveEmbeddedValuesAndExpressions解析默认值，handleNullValue处理null值。
5、创建WebDataBinder，调用convertIfNecessary转换参数类型
AbstractNamedValueMethodArgumentResolver.getNamedValueInfo
private NamedValueInfo getNamedValueInfo(MethodParameter parameter) {
NamedValueInfo namedValueInfo = this.namedValueInfoCache.get(parameter);
if (namedValueInfo == null) {
namedValueInfo = createNamedValueInfo(parameter);
namedValueInfo = updateNamedValueInfo(parameter, namedValueInfo);
this.namedValueInfoCache.put(parameter, namedValueInfo);
}
return namedValueInfo;
}
createNamedValueInfo解析注解的属性。updateNamedValueInfo判断注解中是否设置了name属性，没有设置则获取参数名作为name，将name，required，defaultValue封装成NamedValueInfo。
RequestParamMethodArgumentResolver.createNamedValueInfo(MethodParameter parameter)
protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
RequestParam ann = parameter.getParameterAnnotation(RequestParam.class);
return (ann != null ? new RequestParamNamedValueInfo(ann) : new RequestParamNamedValueInfo());
}
获取@RequestParam注解并创建RequestParamNamedValueInfo。
RequestParamNamedValueInfo(RequestParam annotation)
public RequestParamNamedValueInfo(RequestParam annotation) {
super(annotation.name(), annotation.required(), annotation.defaultValue());
}
设置@RequestParam注解中的name到RequestParamNamedValueInfo。
AbstractNamedValueMethodArgumentResolver.updateNamedValueInfo(MethodParameter parameter, NamedValueInfo info)
private NamedValueInfo updateNamedValueInfo(MethodParameter parameter, NamedValueInfo info) {
String name = info.name;
if (info.name.isEmpty()) {
name = parameter.getParameterName();
if (name == null) {
throw new IllegalArgumentException(
"Name for argument of type [" + parameter.getNestedParameterType().getName() +
"] not specified, and parameter name information not found in class file either.");
}
}
String defaultValue = (ValueConstants.DEFAULT_NONE.equals(info.defaultValue) ? null : info.defaultValue);
return new NamedValueInfo(name, info.required, defaultValue);
}
如果NamedValueInfo中的name为null，即@RequestParam注解没有设置name属性，则获取方法参数名为name，name，required属性和默认值封装成NamedValueInfo。
RequestParamMethodArgumentResolver.resolveName(String name, MethodParameter parameter, NativeWebRequest request)
protected Object resolveName(String name, MethodParameter parameter, NativeWebRequest request) throws Exception {
HttpServletRequest servletRequest = request.getNativeRequest(HttpServletRequest.class);
if (servletRequest != null) {
Object mpArg = MultipartResolutionDelegate.resolveMultipartArgument(name, parameter, servletRequest);
if (mpArg != MultipartResolutionDelegate.UNRESOLVABLE) {
return mpArg;
}
}
Object arg = null;
MultipartRequest multipartRequest = request.getNativeRequest(MultipartRequest.class);
if (multipartRequest != null) {
List<MultipartFile> files = multipartRequest.getFiles(name);
if (!files.isEmpty()) {
arg = (files.size() == 1 ? files.get(0) : files);
}
}
if (arg == null) {
String[] paramValues = request.getParameterValues(name);
if (paramValues != null) {
arg = (paramValues.length == 1 ? paramValues[0] : paramValues);
}
}
return arg;
}
1、MultipartResolutionDelegate.resolveMultipartArgument解析MultipartArgument，如果请求时文件上传，则进入这里进行解析。
2、 multipartRequest.getFiles获取MultipartFile集合，如果请求时文件上传，则进入这里
3、request.getParameterValues通过参数名获取请求中的参数值
