001 // Copyright (c) 2001 Hursh Jain (http://www.mollypages.org)
002 // The Molly framework is freely distributable under the terms of an
003 // MIT-style license. For details, see the molly pages web site at:
004 // http://www.mollypages.org/. Use, modify, have fun !
005
006 package fc.web.page;
007
008 import java.io.*;
009 import java.util.*;
010
011 import javax.servlet.*;
012 import javax.servlet.http.*;
013
014 /**
015 A page is a cool and sane replacement for JSP's with much better syntax.
016 <p>
017 Server side pages implement this interface via the concrete {@link PageImpl}
018 class. This class has some additional utility methods as well that page
019 authors may find useful.
020
021 @author hursh jain
022 */
023 public interface Page
024 {
025 //all pages result in java files with this package name;
026 public static String PACKAGE_NAME = "molly.pages";
027
028 //not used: public static String DEFAULT_ERROR_PAGE = "/molly/error.mp";
029 public static int DEFAULT_BUFFER_SIZE = 8048;
030
031 /**
032 The default mime-type for each page. Usually, there should be no reason
033 to change this. However, if need be, this can be changed via a page
034 compiler directive or turned off entirely. If it's turned off, then the
035 mime-type should be manually specified via the {@link
036 javax.servlet.ServletResponse.setContentType} method.
037 */
038 public static String DEFAULT_MIME_TYPE = "text/html";
039
040 /**
041 The default encoding of the page, specified in the header sent back to
042 the client. This can be changed to utf-8, utf-16 or any other coding by
043 a page directive. Alternately, this can be set to an empty string and a
044 different encoding can also be specified in the <head> section of
045 the html document, for example:
046 <pre>
047 <head><meta http-equiv=content-type content='text/html; charset=UTF-8'></head>
048 </pre>
049 <font color=red>Encodings can be tricky. We are first compiling
050 a page into a java source file, then running the source file and
051 sending it's output to the browser. <b>Read the page
052 <a href="http://www.mollypages.org/page/charset.mp">encoding
053 and charsets</a> if you are using any non-us-ascii or non-
054 ISO-8859-1</b> characters in your molly source page.</font>
055 */
056 public static String DEFAULT_ENCODING = "ISO-8859-1";
057
058 public void render(HttpServletRequest req, HttpServletResponse res) throws Exception;
059
060 /**
061 This method is invoked whenever a page is created and before it
062 is run.
063 <p>
064 Pages should override this method to instantiate/set-up page
065 variables as needed. (pages have no-arg constructors so like
066 most of the servlet API, setup and initialization of variables
067 is done in a init method instead).
068 <p>
069 When overriding this class, you must remember to
070 call: <tt>super.init</tt>
071 <p>
072 The page class is reloaded if the page is modified. Variables
073 should therefore be cleaned up in the {@link destory} method
074 as needed.
075 */
076 public void init(PageServlet servlet, String contextRelativePagePath) throws ServletException;
077
078 /**
079 This method is invoked whenever a page is destoryed/unloaded
080 */
081 public void destroy();
082
083 /**
084 Returns the path to this page from the web servers <i>document root</i>.
085 <p>So for example, if the page is at <code>foo/bar.mp</code> and is running
086 under the webapp context of <code>context1</code>, then the page path
087 will be: <code>/context1/foo/bar.mp</code>. If there is no specific
088 web app (i.e., the most common case of a default "" webapp), then the page
089 path will be <code>/foo/bar.mp</code>
090 <p>
091 This page path is essentially what needs to be typed in the browsers
092 URL window to invoke the page. It's also useful as form action parameters.
093 For example, in a molly page:
094 <blockquote>
095 <pre>
096 ..
097 <form action="[=getPagePath(req)]" method="post">
098 ..
099 </form>
100 </pre>
101 </blockquote>
102 This will submit the form to the same page where the form is defined. This
103 can be hard coded of course but by using <code>getPagePath</code>, the html
104 does not have to be changed if the name of the page changes on disk.
105 */
106 public String getPagePath(HttpServletRequest req);
107
108 /**
109 Returns the real absolute directory path for the {@link #getPagePath PagePath}.
110 <p>
111 So, for example, for a webserver document root at
112 <code>/web/sites/default/</code> and a page located in
113 <code>foo/bar.mp</code>, the real path will be:
114 <code>/web/sites/default/foo/bar.mp</code>
115 */
116 public String getRealPath(HttpServletRequest req);
117
118 /**
119 Redirects the client to the new page location. This is a thin (possibly
120 easier to remember) wrapper around the {@link HttpServletResponse.sendRedirect} method.
121 <p>
122 The location parameter can be relative to the specified request's URI or
123 relative to the context root if it contains a leading '/'. The webapp name
124 (if any) does <b>not</b> have to be specified, the redirect will creates a
125 full URL <u>(including the webapp context path)</u> suitable for this
126 purpose.
127 <p>
128 For example:
129 <style>
130 #redirects {background: #cccccc; }
131 #redirects tr {background: white; }
132 #redirects .head {font-weight: bold; }
133 </style>
134 <table id=redirects border=0 cellspacing=1 cellpadding=7>
135 <tr class=head>
136 <td width="25%">webapp context</td>
137 <td width="25%">current page</td>
138 <td width="25%">location parameter</td>
139 <td width="25%">resulting page</td>
140 </tr>
141 <tr>
142 <td>default web app ("/")</td>
143 <td>foo/bar.mp</td>
144 <td>baz.mp</td>
145 <td>foo/baz.mp</td>
146 </tr>
147 <tr>
148 <td>default web app ("/")</td>
149 <td>foo/bar.mp</td>
150 <td>/baz.mp</td>
151 <td>baz.mp</td>
152 </tr>
153 <tr>
154 <td>/myapp</td>
155 <td>foo/bar.mp</td>
156 <td>baz.mp</td>
157 <td>/myapp/foo/baz.mp</td>
158 </tr>
159 <tr>
160 <td>/myapp</td>
161 <td>foo/bar.mp</td>
162 <td>/baz.mp</td>
163 <td>/myapp/baz.mp</td>
164 </tr>
165 </table>
166
167 @param req the current request
168 @param res the current response
169 @param location location to redirect to.
170 */
171 public void clientRedirect(HttpServletRequest req, HttpServletResponse res, String newLocation) throws IOException;
172
173 /**
174 Returns a thread specific CharArrayWriter that can be passed to this method
175 as various points in the page. The contents of this writer can then be
176 printed on the page when desired.
177 <p>
178 Note: The writer is <b>not</b> reset or flushed when it is retrieved. It
179 must be <font color=blue>reset manually</font> via calling the {@link
180 java.io.CharArrayWriter#reset} method. This design-decision allows request
181 threads to collect debugging data across multiple pages.
182 <p>
183 The suggested usage idiom is:
184 <blockquote>
185 <pre>
186 dbg(true);
187 CharArrayWriter <font color=blue>cw</font> = getThreadLocalWriter():
188 bug(<font color=blue>cw</font>, "some message");
189 ...
190 bug(<font color=blue>cw</font>, "other message");
191 ...
192 <font color=blue>
193 cw.writeTo(out);
194 cw.reset();
195 </font>
196 </pre>
197 </blockquote>
198 */
199 public CharArrayWriter getThreadLocalWriter();
200
201 /*
202 These are in PageImpl but do they need to be in the Page interface as well ?
203 Subject to change so prolly not, thus commented out. hj
204
205 public void startTimer();
206 public long getTime();
207 public void dbg(boolean val);
208 public void dbgPrefix(String dbg_prefix);
209 public void dbgSuffix(String dbg_suffix);
210 public void bug(final Writer writer, final Object str1) throws IOException;
211 public void bug(final Writer writer, final Object str1, final Object str2) throws IOException;
212 public void bug(final Writer writer, final Object str1, final Object str2, final Object str3) throws IOException;
213 public void bug(final Writer writer, final Object str1, final Object str2, final Object str3, final Object... args) throws IOException;
214 */
215 }