001/*
002 * Copyright 2002-2014 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.web.bind.WebDataBinder;
025import org.springframework.web.context.request.NativeWebRequest;
026
027/**
028 * Resolves method arguments annotated with {@code @Value}.
029 *
030 * <p>An {@code @Value} does not have a name but gets resolved from the default
031 * value string, which may contain ${...} placeholder or Spring Expression
032 * Language #{...} expressions.
033 *
034 * <p>A {@link WebDataBinder} may be invoked to apply type conversion to
035 * resolved argument value.
036 *
037 * @author Rossen Stoyanchev
038 * @since 3.1
039 */
040public class ExpressionValueMethodArgumentResolver extends AbstractNamedValueMethodArgumentResolver {
041
042        /**
043         * @param beanFactory a bean factory to use for resolving  ${...}
044         * placeholder and #{...} SpEL expressions in default values;
045         * or {@code null} if default values are not expected to contain expressions
046         */
047        public ExpressionValueMethodArgumentResolver(ConfigurableBeanFactory beanFactory) {
048                super(beanFactory);
049        }
050
051
052        @Override
053        public boolean supportsParameter(MethodParameter parameter) {
054                return parameter.hasParameterAnnotation(Value.class);
055        }
056
057        @Override
058        protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
059                Value annotation = parameter.getParameterAnnotation(Value.class);
060                return new ExpressionValueNamedValueInfo(annotation);
061        }
062
063        @Override
064        protected Object resolveName(String name, MethodParameter parameter, NativeWebRequest webRequest) throws Exception {
065                // No name to resolve
066                return null;
067        }
068
069        @Override
070        protected void handleMissingValue(String name, MethodParameter parameter) throws ServletException {
071                throw new UnsupportedOperationException("@Value is never required: " + parameter.getMethod());
072        }
073
074
075        private static class ExpressionValueNamedValueInfo extends NamedValueInfo {
076
077                private ExpressionValueNamedValueInfo(Value annotation) {
078                        super("@Value", false, annotation.value());
079                }
080        }
081
082}