001/*
002 * Copyright 2002-2017 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.beans.factory.config;
018
019import org.springframework.lang.Nullable;
020import org.springframework.util.StringValueResolver;
021
022/**
023 * {@link StringValueResolver} adapter for resolving placeholders and
024 * expressions against a {@link ConfigurableBeanFactory}.
025 *
026 * <p>Note that this adapter resolves expressions as well, in contrast
027 * to the {@link ConfigurableBeanFactory#resolveEmbeddedValue} method.
028 * The {@link BeanExpressionContext} used is for the plain bean factory,
029 * with no scope specified for any contextual objects to access.
030 *
031 * @author Juergen Hoeller
032 * @since 4.3
033 * @see ConfigurableBeanFactory#resolveEmbeddedValue(String)
034 * @see ConfigurableBeanFactory#getBeanExpressionResolver()
035 * @see BeanExpressionContext
036 */
037public class EmbeddedValueResolver implements StringValueResolver {
038
039        private final BeanExpressionContext exprContext;
040
041        @Nullable
042        private final BeanExpressionResolver exprResolver;
043
044
045        public EmbeddedValueResolver(ConfigurableBeanFactory beanFactory) {
046                this.exprContext = new BeanExpressionContext(beanFactory, null);
047                this.exprResolver = beanFactory.getBeanExpressionResolver();
048        }
049
050
051        @Override
052        @Nullable
053        public String resolveStringValue(String strVal) {
054                String value = this.exprContext.getBeanFactory().resolveEmbeddedValue(strVal);
055                if (this.exprResolver != null && value != null) {
056                        Object evaluated = this.exprResolver.evaluate(value, this.exprContext);
057                        value = (evaluated != null ? evaluated.toString() : null);
058                }
059                return value;
060        }
061
062}