org.springframework.web.reactive.result.method.annotation.ErrorsMethodArgumentResolver.java Source code

Introduction

Here is the source code for org.springframework.web.reactive.result.method.annotation.ErrorsMethodArgumentResolver.java

Source

/*
 * Copyright 2002-2018 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);
        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 = parameter.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;
    }

}