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.web.context.support; 018 019import javax.servlet.ServletContext; 020 021import org.springframework.beans.factory.FactoryBean; 022import org.springframework.lang.Nullable; 023import org.springframework.web.context.ServletContextAware; 024 025/** 026 * {@link FactoryBean} that retrieves a specific ServletContext init parameter 027 * (that is, a "context-param" defined in {@code web.xml}). 028 * Exposes that ServletContext init parameter when used as bean reference, 029 * effectively making it available as named Spring bean instance. 030 * 031 * <p><b>NOTE:</b> As of Spring 3.0, you may also use the "contextParameters" default 032 * bean which is of type Map, and dereference it using an "#{contextParameters.myKey}" 033 * expression to access a specific parameter by name. 034 * 035 * @author Juergen Hoeller 036 * @since 1.2.4 037 * @see org.springframework.web.context.WebApplicationContext#CONTEXT_PARAMETERS_BEAN_NAME 038 * @see ServletContextAttributeFactoryBean 039 */ 040public class ServletContextParameterFactoryBean implements FactoryBean<String>, ServletContextAware { 041 042 @Nullable 043 private String initParamName; 044 045 @Nullable 046 private String paramValue; 047 048 049 /** 050 * Set the name of the ServletContext init parameter to expose. 051 */ 052 public void setInitParamName(String initParamName) { 053 this.initParamName = initParamName; 054 } 055 056 @Override 057 public void setServletContext(ServletContext servletContext) { 058 if (this.initParamName == null) { 059 throw new IllegalArgumentException("initParamName is required"); 060 } 061 this.paramValue = servletContext.getInitParameter(this.initParamName); 062 if (this.paramValue == null) { 063 throw new IllegalStateException("No ServletContext init parameter '" + this.initParamName + "' found"); 064 } 065 } 066 067 068 @Override 069 @Nullable 070 public String getObject() { 071 return this.paramValue; 072 } 073 074 @Override 075 public Class<String> getObjectType() { 076 return String.class; 077 } 078 079 @Override 080 public boolean isSingleton() { 081 return true; 082 } 083 084}