1 /*
2 * $Source: /usr/cvsroot/melati/melati/src/main/java/org/melati/template/TemplateEngine.java,v $
3 * $Revision: 1.40 $
4 *
5 * Copyright (C) 2005 Tim Pizey
6 *
7 * Part of Melati (http://melati.org), a framework for the rapid
8 * development of clean, maintainable web applications.
9 *
10 * Melati is free software; Permission is granted to copy, distribute
11 * and/or modify this software under the terms either:
12 *
13 * a) the GNU General Public License as published by the Free Software
14 * Foundation; either version 2 of the License, or (at your option)
15 * any later version,
16 *
17 * or
18 *
19 * b) any version of the Melati Software License, as published
20 * at http://melati.org
21 *
22 * You should have received a copy of the GNU General Public License and
23 * the Melati Software License along with this program;
24 * if not, write to the Free Software Foundation, Inc.,
25 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA to obtain the
26 * GNU General Public License and visit http://melati.org to obtain the
27 * Melati Software License.
28 *
29 * Feel free to contact the Developers of Melati (http://melati.org),
30 * if you would like to work out a different arrangement than the options
31 * outlined here. It is our intention to allow Melati to be used by as
32 * wide an audience as possible.
33 *
34 * This program is distributed in the hope that it will be useful,
35 * but WITHOUT ANY WARRANTY; without even the implied warranty of
36 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
37 * GNU General Public License for more details.
38 *
39 * Contact details for copyright holder:
40 *
41 * Tim Pizey <timp At paneris.org>
42 * http://paneris.org/~timp
43 */
44 package org.melati.template;
45
46 import java.util.Enumeration;
47
48 import org.melati.Melati;
49 import org.melati.MelatiConfig;
50 import org.melati.util.MelatiStringWriter;
51 import org.melati.util.MelatiWriter;
52
53 /**
54 * A TemplateEngine typically evaluates a template containing variables
55 * against a context containing values for those variables.
56 *
57 * The canonical java Template Engines are WebMacro and Velocity.
58 *
59 * @author timp At paneris.org
60 */
61 public interface TemplateEngine {
62
63 /**
64 * Initialise the Engine.
65 *
66 * @param melatiConfig a {@link MelatiConfig}
67 * @throws TemplateEngineException if any problem occurs with the engine
68 */
69 void init(MelatiConfig melatiConfig) throws TemplateEngineException;
70
71 /**
72 * Create a new Context for this engine.
73 *
74 * @param melati the {@link Melati}
75 * @throws TemplateEngineException if any problem occurs with the engine
76 * @return a {@link TemplateContext}
77 */
78 TemplateContext getTemplateContext(Melati melati)
79 throws TemplateEngineException;
80
81 /**
82 * The name of the template engine (used to find the templets).
83 * @return the name of the current configured template engine
84 */
85 String getName();
86
87 /**
88 * @return the extension of the templates used by this template engine,
89 * including the dot.
90 */
91 String templateExtension();
92
93 /**
94 * A root should not end in a slash.
95 *
96 * @return an Enumeration of string roots, always at least the empty string
97 */
98 Enumeration<String> getRoots();
99
100 /**
101 * Add a template root directory.
102 * NOTE A root should not start or end in a slash.
103 *
104 * @param root the root to add
105 */
106 void addRoot(String root);
107
108 /**
109 * Get a template given it's full name.
110 *
111 * @param templateName the name of the template to find
112 * @throws NotFoundException if template not found
113 * @return a template
114 */
115 Template template(String templateName)
116 throws NotFoundException;
117
118 /**
119 * The name of a template which exists.
120 *
121 * @param key short name, without path or extension
122 * @param classifier a purpose or database name or similar qualifier
123 * @return the name of a template, null if none found
124 */
125 String getTemplateName(String key, String classifier);
126
127 /**
128 * Expand the Template against the context.
129 *
130 * @param out a {@link MelatiWriter} to output on
131 * @param templateName the name of the template to expand
132 * @param templateContext the {@link ServletTemplateContext} to expand
133 * the template against
134 * @throws NotFoundException if template not found
135 */
136 void expandTemplate(MelatiWriter out, String templateName,
137 TemplateContext templateContext) throws NotFoundException;
138
139 /**
140 * Expand the Template against the context, unwrapping any Access Exceptions.
141 *
142 * @param out a {@link MelatiWriter} to output on
143 * @param template the {@link Template} to expand
144 * @param templateContext the {@link ServletTemplateContext} to expand
145 * the template against
146 */
147 void expandTemplate(MelatiWriter out, Template template,
148 TemplateContext templateContext);
149
150 /**
151 * Expand the Template against the context and return the expansion as a string.
152 *
153 * @param template the {@link Template} to expand
154 * @param templateContext the {@link ServletTemplateContext} to expand
155 * the template against
156 * @return the interpolated template as a String
157 */
158 String expandedTemplate(Template template, TemplateContext templateContext);
159
160 /**
161 * @return a {@link MelatiStringWriter}.
162 * @see Melati#getStringWriter()
163 */
164 MelatiStringWriter getStringWriter();
165
166 /**
167 * Get the underlying engine.
168 *
169 * @return the configured template engine
170 */
171 Object getEngine();
172
173 }
174