001/*
002 * Copyright 2002-2018 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.servlet.resource;
018
019import java.io.IOException;
020
021import javax.servlet.RequestDispatcher;
022import javax.servlet.ServletContext;
023import javax.servlet.ServletException;
024import javax.servlet.http.HttpServletRequest;
025import javax.servlet.http.HttpServletResponse;
026
027import org.springframework.lang.Nullable;
028import org.springframework.util.Assert;
029import org.springframework.util.StringUtils;
030import org.springframework.web.HttpRequestHandler;
031import org.springframework.web.context.ServletContextAware;
032
033/**
034 * An {@link HttpRequestHandler} for serving static files using the Servlet container's "default" Servlet.
035 *
036 * <p>This handler is intended to be used with a "/*" mapping when the
037 * {@link org.springframework.web.servlet.DispatcherServlet DispatcherServlet}
038 * is mapped to "/", thus  overriding the Servlet container's default handling of static resources.
039 * The mapping to this handler should generally be ordered as the last in the chain so that it will
040 * only execute when no other more specific mappings (i.e., to controllers) can be matched.
041 *
042 * <p>Requests are handled by forwarding through the {@link RequestDispatcher} obtained via the
043 * name specified through the {@link #setDefaultServletName "defaultServletName" property}.
044 * In most cases, the {@code defaultServletName} does not need to be set explicitly, as the
045 * handler checks at initialization time for the presence of the default Servlet of well-known
046 * containers such as Tomcat, Jetty, Resin, WebLogic and WebSphere. However, when running in a
047 * container where the default Servlet's name is not known, or where it has been customized
048 * via server configuration, the  {@code defaultServletName} will need to be set explicitly.
049 *
050 * @author Jeremy Grelle
051 * @author Juergen Hoeller
052 * @since 3.0.4
053 */
054public class DefaultServletHttpRequestHandler implements HttpRequestHandler, ServletContextAware {
055
056        /** Default Servlet name used by Tomcat, Jetty, JBoss, and GlassFish. */
057        private static final String COMMON_DEFAULT_SERVLET_NAME = "default";
058
059        /** Default Servlet name used by Google App Engine. */
060        private static final String GAE_DEFAULT_SERVLET_NAME = "_ah_default";
061
062        /** Default Servlet name used by Resin. */
063        private static final String RESIN_DEFAULT_SERVLET_NAME = "resin-file";
064
065        /** Default Servlet name used by WebLogic. */
066        private static final String WEBLOGIC_DEFAULT_SERVLET_NAME = "FileServlet";
067
068        /** Default Servlet name used by WebSphere. */
069        private static final String WEBSPHERE_DEFAULT_SERVLET_NAME = "SimpleFileServlet";
070
071
072        @Nullable
073        private String defaultServletName;
074
075        @Nullable
076        private ServletContext servletContext;
077
078
079        /**
080         * Set the name of the default Servlet to be forwarded to for static resource requests.
081         */
082        public void setDefaultServletName(String defaultServletName) {
083                this.defaultServletName = defaultServletName;
084        }
085
086        /**
087         * If the {@code defaultServletName} property has not been explicitly set,
088         * attempts to locate the default Servlet using the known common
089         * container-specific names.
090         */
091        @Override
092        public void setServletContext(ServletContext servletContext) {
093                this.servletContext = servletContext;
094                if (!StringUtils.hasText(this.defaultServletName)) {
095                        if (this.servletContext.getNamedDispatcher(COMMON_DEFAULT_SERVLET_NAME) != null) {
096                                this.defaultServletName = COMMON_DEFAULT_SERVLET_NAME;
097                        }
098                        else if (this.servletContext.getNamedDispatcher(GAE_DEFAULT_SERVLET_NAME) != null) {
099                                this.defaultServletName = GAE_DEFAULT_SERVLET_NAME;
100                        }
101                        else if (this.servletContext.getNamedDispatcher(RESIN_DEFAULT_SERVLET_NAME) != null) {
102                                this.defaultServletName = RESIN_DEFAULT_SERVLET_NAME;
103                        }
104                        else if (this.servletContext.getNamedDispatcher(WEBLOGIC_DEFAULT_SERVLET_NAME) != null) {
105                                this.defaultServletName = WEBLOGIC_DEFAULT_SERVLET_NAME;
106                        }
107                        else if (this.servletContext.getNamedDispatcher(WEBSPHERE_DEFAULT_SERVLET_NAME) != null) {
108                                this.defaultServletName = WEBSPHERE_DEFAULT_SERVLET_NAME;
109                        }
110                        else {
111                                throw new IllegalStateException("Unable to locate the default servlet for serving static content. " +
112                                                "Please set the 'defaultServletName' property explicitly.");
113                        }
114                }
115        }
116
117
118        @Override
119        public void handleRequest(HttpServletRequest request, HttpServletResponse response)
120                        throws ServletException, IOException {
121
122                Assert.state(this.servletContext != null, "No ServletContext set");
123                RequestDispatcher rd = this.servletContext.getNamedDispatcher(this.defaultServletName);
124                if (rd == null) {
125                        throw new IllegalStateException("A RequestDispatcher could not be located for the default servlet '" +
126                                        this.defaultServletName + "'");
127                }
128                rd.forward(request, response);
129        }
130
131}