001/*
002 * Copyright 2002-2018 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.web.reactive.result.method.annotation;
018
019import reactor.core.publisher.Mono;
020
021import org.springframework.core.Conventions;
022import org.springframework.core.MethodParameter;
023import org.springframework.core.ReactiveAdapter;
024import org.springframework.core.ReactiveAdapterRegistry;
025import org.springframework.util.Assert;
026import org.springframework.util.StringUtils;
027import org.springframework.validation.BindingResult;
028import org.springframework.validation.Errors;
029import org.springframework.web.bind.annotation.ModelAttribute;
030import org.springframework.web.reactive.BindingContext;
031import org.springframework.web.reactive.result.method.HandlerMethodArgumentResolverSupport;
032import org.springframework.web.server.ServerWebExchange;
033
034/**
035 * Resolve {@link Errors} or {@link BindingResult} method arguments.
036 * An {@code Errors} argument is expected to appear immediately after the
037 * model attribute in the method signature.
038 *
039 * @author Rossen Stoyanchev
040 * @since 5.0
041 */
042public class ErrorsMethodArgumentResolver extends HandlerMethodArgumentResolverSupport {
043
044        public ErrorsMethodArgumentResolver(ReactiveAdapterRegistry registry) {
045                super(registry);
046        }
047
048
049        @Override
050        public boolean supportsParameter(MethodParameter parameter) {
051                return checkParameterType(parameter, Errors.class::isAssignableFrom);
052        }
053
054        @Override
055        public Mono<Object> resolveArgument(
056                        MethodParameter parameter, BindingContext context, ServerWebExchange exchange) {
057
058                Object errors = getErrors(parameter, context);
059                if (Mono.class.isAssignableFrom(errors.getClass())) {
060                        return ((Mono<?>) errors).cast(Object.class);
061                }
062                else if (Errors.class.isAssignableFrom(errors.getClass())) {
063                        return Mono.just(errors);
064                }
065                else {
066                        throw new IllegalStateException("Unexpected Errors/BindingResult type: " + errors.getClass().getName());
067                }
068        }
069
070        private Object getErrors(MethodParameter parameter, BindingContext context) {
071                Assert.isTrue(parameter.getParameterIndex() > 0,
072                                "Errors argument must be declared immediately after a model attribute argument");
073
074                int index = parameter.getParameterIndex() - 1;
075                MethodParameter attributeParam = MethodParameter.forExecutable(parameter.getExecutable(), index);
076                ReactiveAdapter adapter = getAdapterRegistry().getAdapter(attributeParam.getParameterType());
077
078                Assert.state(adapter == null, "An @ModelAttribute and an Errors/BindingResult argument " +
079                                "cannot both be declared with an async type wrapper. " +
080                                "Either declare the @ModelAttribute without an async wrapper type or " +
081                                "handle a WebExchangeBindException error signal through the async type.");
082
083                ModelAttribute ann = parameter.getParameterAnnotation(ModelAttribute.class);
084                String name = (ann != null && StringUtils.hasText(ann.value()) ?
085                                ann.value() : Conventions.getVariableNameForParameter(attributeParam));
086                Object errors = context.getModel().asMap().get(BindingResult.MODEL_KEY_PREFIX + name);
087
088                Assert.state(errors != null, () -> "An Errors/BindingResult argument is expected " +
089                                "immediately after the @ModelAttribute argument to which it applies. " +
090                                "For @RequestBody and @RequestPart arguments, please declare them with a reactive " +
091                                "type wrapper and use its onError operators to handle WebExchangeBindException: " +
092                                parameter.getMethod());
093
094                return errors;
095        }
096
097}