001/*
002 * Copyright 2002-2015 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.view;
018
019import org.springframework.util.ClassUtils;
020
021/**
022 * Convenient subclass of {@link UrlBasedViewResolver} that supports
023 * {@link InternalResourceView} (i.e. Servlets and JSPs) and subclasses
024 * such as {@link JstlView}.
025 *
026 * <p>The view class for all views generated by this resolver can be specified
027 * via {@link #setViewClass}. See {@link UrlBasedViewResolver}'s javadoc for details.
028 * The default is {@link InternalResourceView}, or {@link JstlView} if the
029 * JSTL API is present.
030 *
031 * <p>BTW, it's good practice to put JSP files that just serve as views under
032 * WEB-INF, to hide them from direct access (e.g. via a manually entered URL).
033 * Only controllers will be able to access them then.
034 *
035 * <p><b>Note:</b> When chaining ViewResolvers, an InternalResourceViewResolver
036 * always needs to be last, as it will attempt to resolve any view name,
037 * no matter whether the underlying resource actually exists.
038 *
039 * @author Juergen Hoeller
040 * @since 17.02.2003
041 * @see #setViewClass
042 * @see #setPrefix
043 * @see #setSuffix
044 * @see #setRequestContextAttribute
045 * @see InternalResourceView
046 * @see JstlView
047 */
048public class InternalResourceViewResolver extends UrlBasedViewResolver {
049
050        private static final boolean jstlPresent = ClassUtils.isPresent(
051                        "javax.servlet.jsp.jstl.core.Config", InternalResourceViewResolver.class.getClassLoader());
052
053        private Boolean alwaysInclude;
054
055
056        /**
057         * Sets the default {@link #setViewClass view class} to {@link #requiredViewClass}:
058         * by default {@link InternalResourceView}, or {@link JstlView} if the JSTL API
059         * is present.
060         */
061        public InternalResourceViewResolver() {
062                Class<?> viewClass = requiredViewClass();
063                if (InternalResourceView.class == viewClass && jstlPresent) {
064                        viewClass = JstlView.class;
065                }
066                setViewClass(viewClass);
067        }
068
069        /**
070         * A convenience constructor that allows for specifying {@link #setPrefix prefix}
071         * and {@link #setSuffix suffix} as constructor arguments.
072         * @param prefix the prefix that gets prepended to view names when building a URL
073         * @param suffix the suffix that gets appended to view names when building a URL
074         * @since 4.3
075         */
076        public InternalResourceViewResolver(String prefix, String suffix) {
077                this();
078                setPrefix(prefix);
079                setSuffix(suffix);
080        }
081
082
083        /**
084         * This resolver requires {@link InternalResourceView}.
085         */
086        @Override
087        protected Class<?> requiredViewClass() {
088                return InternalResourceView.class;
089        }
090
091        /**
092         * Specify whether to always include the view rather than forward to it.
093         * <p>Default is "false". Switch this flag on to enforce the use of a
094         * Servlet include, even if a forward would be possible.
095         * @see InternalResourceView#setAlwaysInclude
096         */
097        public void setAlwaysInclude(boolean alwaysInclude) {
098                this.alwaysInclude = alwaysInclude;
099        }
100
101
102        @Override
103        protected AbstractUrlBasedView buildView(String viewName) throws Exception {
104                InternalResourceView view = (InternalResourceView) super.buildView(viewName);
105                if (this.alwaysInclude != null) {
106                        view.setAlwaysInclude(this.alwaysInclude);
107                }
108                view.setPreventDispatchLoop(true);
109                return view;
110        }
111
112}