Java tutorial
/* * Copyright 2002-2019 the original author or authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * https://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.springframework.web.reactive.result.method.annotation; import java.beans.ConstructorProperties; import java.lang.annotation.Annotation; import java.lang.reflect.Constructor; import java.util.List; import java.util.Map; import java.util.Optional; import reactor.core.publisher.Mono; import reactor.core.publisher.MonoProcessor; import org.springframework.beans.BeanUtils; import org.springframework.core.DefaultParameterNameDiscoverer; import org.springframework.core.MethodParameter; import org.springframework.core.ParameterNameDiscoverer; import org.springframework.core.ReactiveAdapter; import org.springframework.core.ReactiveAdapterRegistry; import org.springframework.core.ResolvableType; import org.springframework.core.annotation.AnnotationUtils; import org.springframework.lang.Nullable; import org.springframework.ui.Model; import org.springframework.util.Assert; import org.springframework.util.ClassUtils; import org.springframework.validation.BindingResult; import org.springframework.validation.Errors; import org.springframework.validation.annotation.Validated; import org.springframework.web.bind.WebDataBinder; import org.springframework.web.bind.annotation.ModelAttribute; import org.springframework.web.bind.support.WebExchangeBindException; import org.springframework.web.bind.support.WebExchangeDataBinder; import org.springframework.web.reactive.BindingContext; import org.springframework.web.reactive.result.method.HandlerMethodArgumentResolverSupport; import org.springframework.web.server.ServerWebExchange; /** * Resolve {@code @ModelAttribute} annotated method arguments. * * <p>Model attributes are sourced from the model, or created using a default * constructor and then added to the model. Once created the attribute is * populated via data binding to the request (form data, query params). * Validation also may be applied if the argument is annotated with * {@code @javax.validation.Valid} or Spring's own * {@code @org.springframework.validation.annotation.Validated}. * * <p>When this handler is created with {@code useDefaultResolution=true} * any non-simple type argument and return value is regarded as a model * attribute with or without the presence of an {@code @ModelAttribute}. * * @author Rossen Stoyanchev * @author Juergen Hoeller * @since 5.0 */ public class ModelAttributeMethodArgumentResolver extends HandlerMethodArgumentResolverSupport { private static final ParameterNameDiscoverer parameterNameDiscoverer = new DefaultParameterNameDiscoverer(); private final boolean useDefaultResolution; /** * Class constructor with a default resolution mode flag. * @param adapterRegistry for adapting to other reactive types from and to Mono * @param useDefaultResolution if "true", non-simple method arguments and * return values are considered model attributes with or without a * {@code @ModelAttribute} annotation present. */ public ModelAttributeMethodArgumentResolver(ReactiveAdapterRegistry adapterRegistry, boolean useDefaultResolution) { super(adapterRegistry); this.useDefaultResolution = useDefaultResolution; } @Override public boolean supportsParameter(MethodParameter parameter) { if (parameter.hasParameterAnnotation(ModelAttribute.class)) { return true; } else if (this.useDefaultResolution) { return checkParameterType(parameter, type -> !BeanUtils.isSimpleProperty(type)); } return false; } @Override public Mono<Object> resolveArgument(MethodParameter parameter, BindingContext context, ServerWebExchange exchange) { ResolvableType type = ResolvableType.forMethodParameter(parameter); Class<?> resolvedType = type.resolve(); ReactiveAdapter adapter = (resolvedType != null ? getAdapterRegistry().getAdapter(resolvedType) : null); ResolvableType valueType = (adapter != null ? type.getGeneric() : type); Assert.state(adapter == null || !adapter.isMultiValue(), () -> getClass().getSimpleName() + " does not support multi-value reactive type wrapper: " + parameter.getGenericParameterType()); String name = ModelInitializer.getNameForParameter(parameter); Mono<?> valueMono = prepareAttributeMono(name, valueType, context, exchange); Map<String, Object> model = context.getModel().asMap(); MonoProcessor<BindingResult> bindingResultMono = MonoProcessor.create(); model.put(BindingResult.MODEL_KEY_PREFIX + name, bindingResultMono); return valueMono.flatMap(value -> { WebExchangeDataBinder binder = context.createDataBinder(exchange, value, name); return binder.bind(exchange).doOnError(bindingResultMono::onError).doOnSuccess(aVoid -> { validateIfApplicable(binder, parameter); BindingResult errors = binder.getBindingResult(); model.put(BindingResult.MODEL_KEY_PREFIX + name, errors); model.put(name, value); bindingResultMono.onNext(errors); }).then(Mono.fromCallable(() -> { BindingResult errors = binder.getBindingResult(); if (adapter != null) { return adapter.fromPublisher( errors.hasErrors() ? Mono.error(new WebExchangeBindException(parameter, errors)) : valueMono); } else { if (errors.hasErrors() && !hasErrorsArgument(parameter)) { throw new WebExchangeBindException(parameter, errors); } return value; } })); }); } private Mono<?> prepareAttributeMono(String attributeName, ResolvableType attributeType, BindingContext context, ServerWebExchange exchange) { Object attribute = context.getModel().asMap().get(attributeName); if (attribute == null) { attribute = findAndRemoveReactiveAttribute(context.getModel(), attributeName); } if (attribute == null) { return createAttribute(attributeName, attributeType.toClass(), context, exchange); } ReactiveAdapter adapter = getAdapterRegistry().getAdapter(null, attribute); if (adapter != null) { Assert.isTrue(!adapter.isMultiValue(), "Data binding only supports single-value async types"); return Mono.from(adapter.toPublisher(attribute)); } else { return Mono.justOrEmpty(attribute); } } @Nullable private Object findAndRemoveReactiveAttribute(Model model, String attributeName) { return model.asMap().entrySet().stream().filter(entry -> { if (!entry.getKey().startsWith(attributeName)) { return false; } ReactiveAdapter adapter = getAdapterRegistry().getAdapter(null, entry.getValue()); if (adapter == null) { return false; } String name = attributeName + ClassUtils.getShortName(adapter.getReactiveType()); return entry.getKey().equals(name); }).findFirst().map(entry -> { // Remove since we will be re-inserting the resolved attribute value model.asMap().remove(entry.getKey()); return entry.getValue(); }).orElse(null); } private Mono<?> createAttribute(String attributeName, Class<?> clazz, BindingContext context, ServerWebExchange exchange) { Constructor<?> ctor = BeanUtils.findPrimaryConstructor(clazz); if (ctor == null) { Constructor<?>[] ctors = clazz.getConstructors(); if (ctors.length == 1) { ctor = ctors[0]; } else { try { ctor = clazz.getDeclaredConstructor(); } catch (NoSuchMethodException ex) { throw new IllegalStateException("No primary or default constructor found for " + clazz, ex); } } } return constructAttribute(ctor, attributeName, context, exchange); } private Mono<?> constructAttribute(Constructor<?> ctor, String attributeName, BindingContext context, ServerWebExchange exchange) { if (ctor.getParameterCount() == 0) { // A single default constructor -> clearly a standard JavaBeans arrangement. return Mono.just(BeanUtils.instantiateClass(ctor)); } // A single data class constructor -> resolve constructor arguments from request parameters. return WebExchangeDataBinder.extractValuesToBind(exchange).map(bindValues -> { ConstructorProperties cp = ctor.getAnnotation(ConstructorProperties.class); String[] paramNames = (cp != null ? cp.value() : parameterNameDiscoverer.getParameterNames(ctor)); Assert.state(paramNames != null, () -> "Cannot resolve parameter names for constructor " + ctor); Class<?>[] paramTypes = ctor.getParameterTypes(); Assert.state(paramNames.length == paramTypes.length, () -> "Invalid number of parameter names: " + paramNames.length + " for constructor " + ctor); Object[] args = new Object[paramTypes.length]; WebDataBinder binder = context.createDataBinder(exchange, null, attributeName); String fieldDefaultPrefix = binder.getFieldDefaultPrefix(); String fieldMarkerPrefix = binder.getFieldMarkerPrefix(); for (int i = 0; i < paramNames.length; i++) { String paramName = paramNames[i]; Class<?> paramType = paramTypes[i]; Object value = bindValues.get(paramName); if (value == null) { if (fieldDefaultPrefix != null) { value = bindValues.get(fieldDefaultPrefix + paramName); } if (value == null && fieldMarkerPrefix != null) { if (bindValues.get(fieldMarkerPrefix + paramName) != null) { value = binder.getEmptyValue(paramType); } } } value = (value instanceof List ? ((List<?>) value).toArray() : value); MethodParameter methodParam = new MethodParameter(ctor, i); if (value == null && methodParam.isOptional()) { args[i] = (methodParam.getParameterType() == Optional.class ? Optional.empty() : null); } else { args[i] = binder.convertIfNecessary(value, paramTypes[i], methodParam); } } return BeanUtils.instantiateClass(ctor, args); }); } private boolean hasErrorsArgument(MethodParameter parameter) { int i = parameter.getParameterIndex(); Class<?>[] paramTypes = parameter.getExecutable().getParameterTypes(); return (paramTypes.length > i + 1 && Errors.class.isAssignableFrom(paramTypes[i + 1])); } private void validateIfApplicable(WebExchangeDataBinder binder, MethodParameter parameter) { for (Annotation ann : parameter.getParameterAnnotations()) { Validated validatedAnn = AnnotationUtils.getAnnotation(ann, Validated.class); if (validatedAnn != null || ann.annotationType().getSimpleName().startsWith("Valid")) { Object hints = (validatedAnn != null ? validatedAnn.value() : AnnotationUtils.getValue(ann)); if (hints != null) { Object[] validationHints = (hints instanceof Object[] ? (Object[]) hints : new Object[] { hints }); binder.validate(validationHints); } else { binder.validate(); } } } } }