forked from spring-projects/spring-framework
/
ErrorsMethodArgumentResolver.java
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/
ErrorsMethodArgumentResolver.java
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/*
* Copyright 2002-2020 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 reactor.core.publisher.Mono;
import org.springframework.core.Conventions;
import org.springframework.core.MethodParameter;
import org.springframework.core.ReactiveAdapter;
import org.springframework.core.ReactiveAdapterRegistry;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;
import org.springframework.validation.BindingResult;
import org.springframework.validation.Errors;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.reactive.BindingContext;
import org.springframework.web.reactive.result.method.HandlerMethodArgumentResolverSupport;
import org.springframework.web.server.ServerWebExchange;
/**
* Resolve {@link Errors} or {@link BindingResult} method arguments.
* An {@code Errors} argument is expected to appear immediately after the
* model attribute in the method signature.
*
* @author Rossen Stoyanchev
* @since 5.0
*/
public class ErrorsMethodArgumentResolver extends HandlerMethodArgumentResolverSupport {
public ErrorsMethodArgumentResolver(ReactiveAdapterRegistry registry) {
super(registry);
}
@Override
public boolean supportsParameter(MethodParameter parameter) {
return checkParameterType(parameter, Errors.class::isAssignableFrom);
}
@Override
public Mono<Object> resolveArgument(
MethodParameter parameter, BindingContext context, ServerWebExchange exchange) {
Object errors = getErrors(parameter, context);
// Initially ModelAttributeMethodArgumentResolver adds Errors/BindingResult as a
// Mono in the model even if it can't be declared as such on a controller method.
// This is done to enable early argument resolution here. When the Mono actually
// completes it is replaced in the model with the actual value.
if (Mono.class.isAssignableFrom(errors.getClass())) {
return ((Mono<?>) errors).cast(Object.class);
}
else if (Errors.class.isAssignableFrom(errors.getClass())) {
return Mono.just(errors);
}
else {
throw new IllegalStateException("Unexpected Errors/BindingResult type: " + errors.getClass().getName());
}
}
private Object getErrors(MethodParameter parameter, BindingContext context) {
Assert.isTrue(parameter.getParameterIndex() > 0,
"Errors argument must be declared immediately after a model attribute argument");
int index = parameter.getParameterIndex() - 1;
MethodParameter attributeParam = MethodParameter.forExecutable(parameter.getExecutable(), index);
ReactiveAdapter adapter = getAdapterRegistry().getAdapter(attributeParam.getParameterType());
Assert.state(adapter == null, "An @ModelAttribute and an Errors/BindingResult argument " +
"cannot both be declared with an async type wrapper. " +
"Either declare the @ModelAttribute without an async wrapper type or " +
"handle a WebExchangeBindException error signal through the async type.");
ModelAttribute ann = attributeParam.getParameterAnnotation(ModelAttribute.class);
String name = (ann != null && StringUtils.hasText(ann.value()) ?
ann.value() : Conventions.getVariableNameForParameter(attributeParam));
Object errors = context.getModel().asMap().get(BindingResult.MODEL_KEY_PREFIX + name);
Assert.state(errors != null, () -> "An Errors/BindingResult argument is expected " +
"immediately after the @ModelAttribute argument to which it applies. " +
"For @RequestBody and @RequestPart arguments, please declare them with a reactive " +
"type wrapper and use its onError operators to handle WebExchangeBindException: " +
parameter.getMethod());
return errors;
}
}