1 /*
2 * $Id: FreeMarkerAttributeRenderer.java 821299 2009-10-03 12:15:05Z apetrelli $
3 *
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
19 * under the License.
20 */
21
22 package org.apache.tiles.freemarker.renderer;
23
24 import java.io.IOException;
25 import java.util.Enumeration;
26 import java.util.HashMap;
27 import java.util.Map;
28
29 import javax.servlet.ServletConfig;
30 import javax.servlet.ServletContext;
31 import javax.servlet.ServletException;
32 import javax.servlet.http.HttpServletRequest;
33 import javax.servlet.http.HttpServletResponse;
34
35 import org.apache.tiles.Attribute;
36 import org.apache.tiles.context.TilesRequestContext;
37 import org.apache.tiles.freemarker.FreeMarkerTilesException;
38 import org.apache.tiles.freemarker.servlet.TilesFreemarkerServlet;
39 import org.apache.tiles.impl.InvalidTemplateException;
40 import org.apache.tiles.renderer.impl.AbstractTypeDetectingAttributeRenderer;
41 import org.apache.tiles.servlet.context.ExternalWriterHttpServletResponse;
42 import org.apache.tiles.servlet.context.ServletTilesRequestContext;
43 import org.apache.tiles.servlet.context.ServletUtil;
44 import org.apache.tiles.util.IteratorEnumeration;
45
46 /**
47 * FreeMarker renderer for rendering FreeMarker templates as Tiles attributes.
48 * It is only usable under a Servlet environment, because it uses
49 * {@link TilesFreemarkerServlet} internally to forward the request.<br/>
50 * To initialize it correctly, call {@link #setParameter(String, String)} for all the
51 * parameters that you want to set, and then call {@link #commit()}.
52 *
53 * @version $Rev: 821299 $ $Date: 2009-10-03 14:15:05 +0200 (sab, 03 ott 2009) $
54 * @since 2.2.0
55 */
56 public class FreeMarkerAttributeRenderer extends AbstractTypeDetectingAttributeRenderer {
57
58 /**
59 * The servlet that is used to forward the request to.
60 */
61 private AttributeValueFreemarkerServlet servlet;
62
63 /**
64 * The initialization parameters.
65 */
66 private Map<String, String> params = new HashMap<String, String>();
67
68 /**
69 * Sets a parameter for the internal servlet.
70 *
71 * @param key The name of the parameter.
72 * @param value The value of the parameter.
73 * @since 2.2.0
74 */
75 public void setParameter(String key, String value) {
76 params.put(key, value);
77 }
78
79 /**
80 * Commits the parameters and makes this renderer ready for the use.
81 *
82 * @since 2.2.0
83 */
84 public void commit() {
85 servlet = new AttributeValueFreemarkerServlet();
86 try {
87 servlet.init(new InitParamsServletConfig());
88 } catch (ServletException e) {
89 throw new FreeMarkerTilesException(
90 "Cannot initialize internal servlet", e);
91 }
92 }
93
94 /** {@inheritDoc} */
95 @Override
96 public void write(Object value, Attribute attribute,
97 TilesRequestContext request) throws IOException {
98 if (value != null) {
99 if (value instanceof String) {
100 ServletTilesRequestContext servletRequest = ServletUtil.getServletRequest(request);
101 HttpServletRequest httpRequest = servletRequest.getRequest();
102 HttpServletResponse httpResponse = servletRequest.getResponse();
103 servlet.setValue((String) value);
104 try {
105 servlet.doGet(httpRequest,
106 new ExternalWriterHttpServletResponse(httpResponse,
107 request.getPrintWriter()));
108 } catch (ServletException e) {
109 throw new FreeMarkerTilesException("Exception when rendering a FreeMarker attribute", e);
110 }
111 } else {
112 throw new InvalidTemplateException(
113 "Cannot render a template that is not a string: "
114 + value.toString());
115 }
116 } else {
117 throw new InvalidTemplateException("Cannot render a null template");
118 }
119 }
120
121 /** {@inheritDoc} */
122 public boolean isRenderable(Object value, Attribute attribute,
123 TilesRequestContext request) {
124 if (value instanceof String) {
125 String string = (String) value;
126 return string.startsWith("/") && string.endsWith(".ftl");
127 }
128 return false;
129 }
130
131 /**
132 * Extends {@link TilesFreemarkerServlet} to use the attribute value as the template name.
133 *
134 * @since 2.2.0
135 */
136 private static class AttributeValueFreemarkerServlet extends TilesFreemarkerServlet {
137
138 /**
139 * Holds the value that should be used as the template name.
140 */
141 private ThreadLocal<String> valueHolder = new ThreadLocal<String>();
142
143 /**
144 * Sets the value to use as the template name.
145 *
146 * @param value The template name.
147 * @since 2.2.0
148 */
149 public void setValue(String value) {
150 valueHolder.set(value);
151 }
152
153 /** {@inheritDoc} */
154 @Override
155 protected String requestUrlToTemplatePath(HttpServletRequest request) {
156 return valueHolder.get();
157 }
158 }
159
160 /**
161 * Implements {@link ServletConfig} to initialize the internal servlet using parameters
162 * set through {@link FreeMarkerAttributeRenderer#setParameter(String, String)}.
163 *
164 * @version $Rev: 821299 $ $Date: 2009-10-03 14:15:05 +0200 (sab, 03 ott 2009) $
165 * @since 2.2.0
166 */
167 private class InitParamsServletConfig implements ServletConfig {
168
169 /** {@inheritDoc} */
170 public String getInitParameter(String name) {
171 return params.get(name);
172 }
173
174 /** {@inheritDoc} */
175 @SuppressWarnings("unchecked")
176 public Enumeration getInitParameterNames() {
177 return new IteratorEnumeration(params.keySet().iterator());
178 }
179
180 /** {@inheritDoc} */
181 public ServletContext getServletContext() {
182 return ServletUtil.getServletContext(applicationContext);
183 }
184
185 /** {@inheritDoc} */
186 public String getServletName() {
187 return "FreeMarker Attribute Renderer";
188 }
189 }
190 }