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 java.util.Enumeration; 020import java.util.Map; 021import javax.servlet.ServletException; 022import javax.servlet.http.HttpServletRequest; 023import javax.servlet.http.HttpServletResponse; 024import javax.servlet.http.HttpSession; 025 026import org.springframework.web.servlet.support.RequestContext; 027 028/** 029 * Adapter base class for template-based view technologies such as 030 * Velocity and FreeMarker, with the ability to use request and session 031 * attributes in their model and the option to expose helper objects 032 * for Spring's Velocity/FreeMarker macro library. 033 * 034 * <p>JSP/JSTL and other view technologies automatically have access to the 035 * HttpServletRequest object and thereby the request/session attributes 036 * for the current user. Furthermore, they are able to create and cache 037 * helper objects as request attributes themselves. 038 * 039 * @author Juergen Hoeller 040 * @author Darren Davison 041 * @since 1.0.2 042 * @see AbstractTemplateViewResolver 043 * @see org.springframework.web.servlet.view.velocity.VelocityView 044 * @see org.springframework.web.servlet.view.freemarker.FreeMarkerView 045 */ 046public abstract class AbstractTemplateView extends AbstractUrlBasedView { 047 048 /** 049 * Variable name of the RequestContext instance in the template model, 050 * available to Spring's macros: e.g. for creating BindStatus objects. 051 */ 052 public static final String SPRING_MACRO_REQUEST_CONTEXT_ATTRIBUTE = "springMacroRequestContext"; 053 054 055 private boolean exposeRequestAttributes = false; 056 057 private boolean allowRequestOverride = false; 058 059 private boolean exposeSessionAttributes = false; 060 061 private boolean allowSessionOverride = false; 062 063 private boolean exposeSpringMacroHelpers = true; 064 065 066 /** 067 * Set whether all request attributes should be added to the 068 * model prior to merging with the template. Default is "false". 069 */ 070 public void setExposeRequestAttributes(boolean exposeRequestAttributes) { 071 this.exposeRequestAttributes = exposeRequestAttributes; 072 } 073 074 /** 075 * Set whether HttpServletRequest attributes are allowed to override (hide) 076 * controller generated model attributes of the same name. Default is "false", 077 * which causes an exception to be thrown if request attributes of the same 078 * name as model attributes are found. 079 */ 080 public void setAllowRequestOverride(boolean allowRequestOverride) { 081 this.allowRequestOverride = allowRequestOverride; 082 } 083 084 /** 085 * Set whether all HttpSession attributes should be added to the 086 * model prior to merging with the template. Default is "false". 087 */ 088 public void setExposeSessionAttributes(boolean exposeSessionAttributes) { 089 this.exposeSessionAttributes = exposeSessionAttributes; 090 } 091 092 /** 093 * Set whether HttpSession attributes are allowed to override (hide) 094 * controller generated model attributes of the same name. Default is "false", 095 * which causes an exception to be thrown if session attributes of the same 096 * name as model attributes are found. 097 */ 098 public void setAllowSessionOverride(boolean allowSessionOverride) { 099 this.allowSessionOverride = allowSessionOverride; 100 } 101 102 /** 103 * Set whether to expose a RequestContext for use by Spring's macro library, 104 * under the name "springMacroRequestContext". Default is "true". 105 * <p>Currently needed for Spring's Velocity and FreeMarker default macros. 106 * Note that this is <i>not</i> required for templates that use HTML 107 * forms <i>unless</i> you wish to take advantage of the Spring helper macros. 108 * @see #SPRING_MACRO_REQUEST_CONTEXT_ATTRIBUTE 109 */ 110 public void setExposeSpringMacroHelpers(boolean exposeSpringMacroHelpers) { 111 this.exposeSpringMacroHelpers = exposeSpringMacroHelpers; 112 } 113 114 115 @Override 116 protected final void renderMergedOutputModel( 117 Map<String, Object> model, HttpServletRequest request, HttpServletResponse response) throws Exception { 118 119 if (this.exposeRequestAttributes) { 120 for (Enumeration<String> en = request.getAttributeNames(); en.hasMoreElements();) { 121 String attribute = en.nextElement(); 122 if (model.containsKey(attribute) && !this.allowRequestOverride) { 123 throw new ServletException("Cannot expose request attribute '" + attribute + 124 "' because of an existing model object of the same name"); 125 } 126 Object attributeValue = request.getAttribute(attribute); 127 if (logger.isDebugEnabled()) { 128 logger.debug("Exposing request attribute '" + attribute + 129 "' with value [" + attributeValue + "] to model"); 130 } 131 model.put(attribute, attributeValue); 132 } 133 } 134 135 if (this.exposeSessionAttributes) { 136 HttpSession session = request.getSession(false); 137 if (session != null) { 138 for (Enumeration<String> en = session.getAttributeNames(); en.hasMoreElements();) { 139 String attribute = en.nextElement(); 140 if (model.containsKey(attribute) && !this.allowSessionOverride) { 141 throw new ServletException("Cannot expose session attribute '" + attribute + 142 "' because of an existing model object of the same name"); 143 } 144 Object attributeValue = session.getAttribute(attribute); 145 if (logger.isDebugEnabled()) { 146 logger.debug("Exposing session attribute '" + attribute + 147 "' with value [" + attributeValue + "] to model"); 148 } 149 model.put(attribute, attributeValue); 150 } 151 } 152 } 153 154 if (this.exposeSpringMacroHelpers) { 155 if (model.containsKey(SPRING_MACRO_REQUEST_CONTEXT_ATTRIBUTE)) { 156 throw new ServletException( 157 "Cannot expose bind macro helper '" + SPRING_MACRO_REQUEST_CONTEXT_ATTRIBUTE + 158 "' because of an existing model object of the same name"); 159 } 160 // Expose RequestContext instance for Spring macros. 161 model.put(SPRING_MACRO_REQUEST_CONTEXT_ATTRIBUTE, 162 new RequestContext(request, response, getServletContext(), model)); 163 } 164 165 applyContentType(response); 166 167 renderMergedTemplateModel(model, request, response); 168 } 169 170 /** 171 * Apply this view's content type as specified in the "contentType" 172 * bean property to the given response. 173 * <p>Only applies the view's contentType if no content type has been 174 * set on the response before. This allows handlers to override the 175 * default content type beforehand. 176 * @param response current HTTP response 177 * @see #setContentType 178 */ 179 protected void applyContentType(HttpServletResponse response) { 180 if (response.getContentType() == null) { 181 response.setContentType(getContentType()); 182 } 183 } 184 185 /** 186 * Subclasses must implement this method to actually render the view. 187 * @param model combined output Map, with request attributes and 188 * session attributes merged into it if required 189 * @param request current HTTP request 190 * @param response current HTTP response 191 * @throws Exception if rendering failed 192 */ 193 protected abstract void renderMergedTemplateModel( 194 Map<String, Object> model, HttpServletRequest request, HttpServletResponse response) throws Exception; 195 196}