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.method.annotation;
018
019import javax.servlet.ServletException;
020
021import org.springframework.beans.factory.annotation.Value;
022import org.springframework.beans.factory.config.ConfigurableBeanFactory;
023import org.springframework.core.MethodParameter;
024import org.springframework.lang.Nullable;
025import org.springframework.util.Assert;
026import org.springframework.web.bind.WebDataBinder;
027import org.springframework.web.context.request.NativeWebRequest;
028
029/**
030 * Resolves method arguments annotated with {@code @Value}.
031 *
032 * <p>An {@code @Value} does not have a name but gets resolved from the default
033 * value string, which may contain ${...} placeholder or Spring Expression
034 * Language #{...} expressions.
035 *
036 * <p>A {@link WebDataBinder} may be invoked to apply type conversion to
037 * resolved argument value.
038 *
039 * @author Rossen Stoyanchev
040 * @since 3.1
041 */
042public class ExpressionValueMethodArgumentResolver extends AbstractNamedValueMethodArgumentResolver {
043
044        /**
045         * Create a new {@link ExpressionValueMethodArgumentResolver} instance.
046         * @param beanFactory a bean factory to use for resolving  ${...}
047         * placeholder and #{...} SpEL expressions in default values;
048         * or {@code null} if default values are not expected to contain expressions
049         */
050        public ExpressionValueMethodArgumentResolver(@Nullable ConfigurableBeanFactory beanFactory) {
051                super(beanFactory);
052        }
053
054
055        @Override
056        public boolean supportsParameter(MethodParameter parameter) {
057                return parameter.hasParameterAnnotation(Value.class);
058        }
059
060        @Override
061        protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
062                Value ann = parameter.getParameterAnnotation(Value.class);
063                Assert.state(ann != null, "No Value annotation");
064                return new ExpressionValueNamedValueInfo(ann);
065        }
066
067        @Override
068        @Nullable
069        protected Object resolveName(String name, MethodParameter parameter, NativeWebRequest webRequest) throws Exception {
070                // No name to resolve
071                return null;
072        }
073
074        @Override
075        protected void handleMissingValue(String name, MethodParameter parameter) throws ServletException {
076                throw new UnsupportedOperationException("@Value is never required: " + parameter.getMethod());
077        }
078
079
080        private static final class ExpressionValueNamedValueInfo extends NamedValueInfo {
081
082                private ExpressionValueNamedValueInfo(Value annotation) {
083                        super("@Value", false, annotation.value());
084                }
085        }
086
087}