001/*
002 * Copyright 2002-2012 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.context.support;
018
019import javax.servlet.ServletContext;
020
021import org.springframework.beans.factory.FactoryBean;
022import org.springframework.web.context.ServletContextAware;
023
024/**
025 * {@link FactoryBean} that retrieves a specific ServletContext init parameter
026 * (that is, a "context-param" defined in {@code web.xml}).
027 * Exposes that ServletContext init parameter when used as bean reference,
028 * effectively making it available as named Spring bean instance.
029 *
030 * <p><b>NOTE:</b> As of Spring 3.0, you may also use the "contextParameters" default
031 * bean which is of type Map, and dereference it using an "#{contextParameters.myKey}"
032 * expression to access a specific parameter by name.
033 *
034 * @author Juergen Hoeller
035 * @since 1.2.4
036 * @see org.springframework.web.context.WebApplicationContext#CONTEXT_PARAMETERS_BEAN_NAME
037 * @see ServletContextAttributeFactoryBean
038 */
039public class ServletContextParameterFactoryBean implements FactoryBean<String>, ServletContextAware {
040
041        private String initParamName;
042
043        private String paramValue;
044
045
046        /**
047         * Set the name of the ServletContext init parameter to expose.
048         */
049        public void setInitParamName(String initParamName) {
050                this.initParamName = initParamName;
051        }
052
053        @Override
054        public void setServletContext(ServletContext servletContext) {
055                if (this.initParamName == null) {
056                        throw new IllegalArgumentException("initParamName is required");
057                }
058                this.paramValue = servletContext.getInitParameter(this.initParamName);
059                if (this.paramValue == null) {
060                        throw new IllegalStateException("No ServletContext init parameter '" + this.initParamName + "' found");
061                }
062        }
063
064
065        @Override
066        public String getObject() {
067                return this.paramValue;
068        }
069
070        @Override
071        public Class<String> getObjectType() {
072                return String.class;
073        }
074
075        @Override
076        public boolean isSingleton() {
077                return true;
078        }
079
080}