/*
 * 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
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package org.springframework.web.method.annotation;

import javax.servlet.ServletException;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.core.MethodParameter;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.context.request.NativeWebRequest;

Resolves method arguments annotated with @Value.

An @Value does not have a name but gets resolved from the default value string, which may contain ${...} placeholder or Spring Expression Language #{...} expressions.

A WebDataBinder may be invoked to apply type conversion to resolved argument value.

Author:Rossen Stoyanchev
Since:3.1
/** * Resolves method arguments annotated with {@code @Value}. * * <p>An {@code @Value} does not have a name but gets resolved from the default * value string, which may contain ${...} placeholder or Spring Expression * Language #{...} expressions. * * <p>A {@link WebDataBinder} may be invoked to apply type conversion to * resolved argument value. * * @author Rossen Stoyanchev * @since 3.1 */
public class ExpressionValueMethodArgumentResolver extends AbstractNamedValueMethodArgumentResolver {
Params:
  • beanFactory – a bean factory to use for resolving ${...} placeholder and #{...} SpEL expressions in default values; or null if default values are not expected to contain expressions
/** * Create a new {@link ExpressionValueMethodArgumentResolver} instance. * @param beanFactory a bean factory to use for resolving ${...} * placeholder and #{...} SpEL expressions in default values; * or {@code null} if default values are not expected to contain expressions */
public ExpressionValueMethodArgumentResolver(@Nullable ConfigurableBeanFactory beanFactory) { super(beanFactory); } @Override public boolean supportsParameter(MethodParameter parameter) { return parameter.hasParameterAnnotation(Value.class); } @Override protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) { Value ann = parameter.getParameterAnnotation(Value.class); Assert.state(ann != null, "No Value annotation"); return new ExpressionValueNamedValueInfo(ann); } @Override @Nullable protected Object resolveName(String name, MethodParameter parameter, NativeWebRequest webRequest) throws Exception { // No name to resolve return null; } @Override protected void handleMissingValue(String name, MethodParameter parameter) throws ServletException { throw new UnsupportedOperationException("@Value is never required: " + parameter.getMethod()); } private static final class ExpressionValueNamedValueInfo extends NamedValueInfo { private ExpressionValueNamedValueInfo(Value annotation) { super("@Value", false, annotation.value()); } } }