spring-graphql ContextValueMethodArgumentResolver 源码

spring-graphql ContextValueMethodArgumentResolver 代码

文件路径：/spring-graphql/src/main/java/org/springframework/graphql/data/method/annotation/support/ContextValueMethodArgumentResolver.java

/*
 * Copyright 2002-2022 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.graphql.data.method.annotation.support;

import java.lang.annotation.Annotation;
import java.util.Optional;

import graphql.GraphQLContext;
import graphql.schema.DataFetchingEnvironment;
import reactor.core.publisher.Mono;

import org.springframework.core.MethodParameter;
import org.springframework.graphql.data.method.HandlerMethodArgumentResolver;
import org.springframework.graphql.data.method.annotation.ContextValue;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;


/**
 * Resolver for a {@link ContextValue @ContextValue} annotated method parameter.
 *
 * @author Rossen Stoyanchev
 * @since 1.0.0
 */
public class ContextValueMethodArgumentResolver implements HandlerMethodArgumentResolver {

	@Override
	public boolean supportsParameter(MethodParameter parameter) {
		return (parameter.getParameterAnnotation(ContextValue.class) != null);
	}

	@Override
	public Object resolveArgument(MethodParameter parameter, DataFetchingEnvironment environment) {

		ContextValue annotation = parameter.getParameterAnnotation(ContextValue.class);
		Assert.state(annotation != null, "Expected @ContextValue annotation");
		String name = getContextValueName(parameter, annotation.name(), annotation);

		return resolveContextValue(name, annotation.required(), parameter, environment.getGraphQlContext());
	}

	static String getContextValueName(MethodParameter parameter, String nameFromAnnotation, Annotation annotation) {
		if (StringUtils.hasText(nameFromAnnotation)) {
			return nameFromAnnotation;
		}
		String parameterName = parameter.getParameterName();
		if (parameterName != null) {
			return parameterName;
		}
		throw new IllegalArgumentException("Name for " + annotation.getClass().getSimpleName() + " argument " +
				"of type [" + parameter.getNestedParameterType().getName() + "] not specified, " +
				"and parameter name information not found in class file either.");
	}

	@Nullable
	static Object resolveContextValue(
			String contextValueName, boolean required, MethodParameter parameter,
			@Nullable GraphQLContext graphQlContext) {

		Class<?> parameterType = parameter.getParameterType();
		Object value = (graphQlContext != null ? graphQlContext.get(contextValueName) : null);

		boolean isOptional = parameterType.equals(Optional.class);
		boolean isMono = parameterType.equals(Mono.class);

		if (value == null && required && !isOptional && !isMono) {
			throw new IllegalStateException("Missing required context value for " + parameter);
		}

		if (isMono) {
			if (value == null) {
				value = Mono.empty();
			}
			else if (!( value instanceof Mono)) {
				value = Mono.just(value);
			}
			return Mono.just(value);
		}

		if (isOptional) {
			return (value instanceof Optional ? value : Optional.ofNullable(value));
		}

		return value;
	}

}

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