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From jkuhn...@apache.org
Subject svn commit: r420925 [4/9] - /tapestry/tapestry4/trunk/src/site/xdoc/UsersGuide/
Date Tue, 11 Jul 2006 16:54:18 GMT
Modified: tapestry/tapestry4/trunk/src/site/xdoc/UsersGuide/localization.xml
URL: http://svn.apache.org/viewvc/tapestry/tapestry4/trunk/src/site/xdoc/UsersGuide/localization.xml?rev=420925&r1=420924&r2=420925&view=diff
==============================================================================
--- tapestry/tapestry4/trunk/src/site/xdoc/UsersGuide/localization.xml (original)
+++ tapestry/tapestry4/trunk/src/site/xdoc/UsersGuide/localization.xml Tue Jul 11 09:54:16 2006
@@ -1,330 +1,480 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!-- 
-   Copyright 2005 The Apache Software Foundation
-
-   Licensed under the Apache License, Version 2.0 (the "License");
-   you may not use this file except in compliance with the License.
-   You may obtain a copy of the License at
-
-       http://www.apache.org/licenses/LICENSE-2.0
-
-   Unless required by applicable law or agreed to in writing, software
-   distributed under the License is distributed on an "AS IS" BASIS,
-   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-   See the License for the specific language governing permissions and
-   limitations under the License.
--->
-<document>
-<properties>
-<title>Localization</title>
-</properties>
-<body>
-    <p> Proper localization is a pervasive aspect of web application development. Supporting users from different countries, with different languages, can be a tricky proposition ... it is more than just text that must be localized, but more subtle aspects of the application such as date and currency formats. It is also more than text ... in some cases, a localized application will want to change images or even color schemes. </p>
-    <p> Localization support in Tapestry is likewise pervasive. </p>
-    <section name="Component Message Catalogs">
-      
-      <p> The most fundamental aspect of localization in Tapestry are component message catalogs (remember that pages are components too). A message catalog is a mapping from a logical key (that may appear in Java code or in OGNL expressions) to a literal string. Tapestry message catalogs are similar to Java's ResourceBundle class, except there is more flexibility in the character set of the files, and the location of the files. </p>
-      <p> Each component <em>may</em> have a message catalog, consisting of a set of localized message properties files. </p>
-      <p> These files are stored with the page or component specification file. They are named the same as the specification file, but with a different extension (".properties" instead of ".jwc" or ".page"). </p>
-      <p> In addition, this is a <em>set</em> of files; a locale string may be inserted just before the extension. For example, <code>WEB-INF/Home_fr.properties</code> to contain the French language localization of the keys. </p>
-      <p> As with Java's ResourceBundle, resolution of a key to a message starts with the most 
-        <em>specific</em> properties file. Any key not found there will be searched for in less specific files.  For example,
-        the search path could be <code>Home_fr_BE.properties</code>, <code>Home_fr.properties</code>, <code>Home.properties</code>.</p>
-        <p>If a properties file does not exist, that's perfectly ok, the search will continue.</p>
-      <p>
-        When a key can not be found even in the most general properties file, a search occurs in the
-        <a href="#localization.namespace">namespace</a>. In this way, very common strings can be
-        stored and localized once, and used throughout a library or application.
-      </p>
-      <p> We'll describe how to use the message catalog shortly, but first some notes on how the message catalogs are read. </p>
-      <subsection name="Properties file encoding">
-        
-        <p> For Java's ResourceBundle, the properties files must be in UTF-8 character set. This can be problematic, as in non-western languages it is necessary to use Java's native2ascii tool to convert from non-native files into an ASCII encoding of UTF-8. </p>
-        <p> Tapestry can read properties files in alternate character sets, but must be told what character set the file is encoded in (internally, the contents must be converted into standard multi-byte Unicode). </p>
-        <p> This is accomplished by providing some metadata inside the component (or page) specification. Metadata is specified using the <a href="spec.html#spec.meta">&lt;meta&gt;</a> element. </p>
-        <p> The resolution of the character set is somewhat complicated; it is  possible that each properties file will use a different 
-          character set. At the same time, repetition is bad ... therefore it is possible to specify some of this information
-          in the namespace meta data (in the containing application or library specification) so that it can apply to all pages
-          and components within the namespace.</p>
-          
-        <p>
-          The basic meta-data  property name searched for is <code>org.apache.tapestry.messages-encoding</code>.  The value for this name
-          is the name of the charset for the properties file.
-        </p>
-        
-        <p>
-          However, the base name is modified to reflect the locale for the file being read; the locale string is appended
-          to the key, thus <code>org.apache.tapestry.messages-encoding_fr</code> will define the character set for
-          the file <code>WEB-INF/Home_fr.properties</code>
-        </p>
-        
-        <p>
-          For each localization of the base property name, a search of the following locations takes place.
-        </p>
-        <ul>
-          <li>The page or component specification.</li>
-          <li>The namespace (library or application) specification for the namespace containing the page or component.</li>
-          <li>The <a href="configuration.html#configuration.global-property-source">global property source</a>.</li>
-        </ul>
-        
-        <p>
-          Because localization of templates is similar to
-          localization of message properties files,
-          a second search occurs if the search for (variations of)
-          <code>org.apache.tapestry.messages-encoding</code> fails; this time for
-          <code>org.apache.tapestry.template-encoding</code> occurs (again, with variations
-          for each locale).
-        </p>
-        
-        <p>
-          The ultimate default for encoding character set is
-          ISO-8859-1; in other words, the same behavior as reading an ordinary
-          Java ResourceBundle.
-        </p>
-          
-      </subsection>
-    </section>
-    <section name="Missing keys">
-      
-      
-      <p>
-        While developing, you may occasionally reference a key that does not exist. Rather than fail  with an exception,
-        Tapestry will fabricate a missing key value.  This is the key, converted to upper-case, and surrounded with brackets.  For example,
-        <code>[A-MISSING-KEY]</code>.  This allows missing key values to stand out an demand to be fixed, without
-        completely subverting your application.
-      </p>
-      
-    </section> <!-- localization.missing-keys -->
-    <section name="Namespace message catalogs">
-      
-      
-      <p>
-      It is very likely that you'll have a number of strings that are used, and re-used, throughout
-      your application. Rather than duplicate the same message keys and localized values in all your page
-      and component message catalogs, you can put these into your <em>namespace</em> catalog.
-      </p>
-      
-      <p>
-        Each page and component is part of a <code>namespace</code>, identified by
-        a library specification or component specification.
-      </p>
-      
-      <p>
-        The specification may also have a message catalog; for instance, for <code>WEB-INF/myapp.application</code>,
-        the files would be named <code>WEB-INF/myapp.properties</code>, etc. Again, the 
-        name of the file  is based on the servlet name ("myapp").
-      </p>
-      
-      <p>
-        Very simple applications may not have an application specification, but may still have
-        properties, just as if the application specification existed.
-      </p>
-      
-    </section> <!-- localization.namespace -->
-    <!-- localization.component-catalog -->
-    <section name="Template text localization">
-      
-      <p>As described in <a href="template.html#template.directives.l10n">the discussion of Tapestry templates</a>, 
-        static text in an HTML template can be enclosed in a specialized &lt;span&gt; tag. </p>
-      
-    </section>
+    Copyright 2005 The Apache Software Foundation
     
-    <section name="Localized templates">
-      
-      
-      <p>
-        In some cases, the entire layout of a page (or component) must change due to locale. For example,
-        because of differences between western languages (which read left to right) and many eastern
-        languages (which read right to left).
-      </p>
-      
-      <p>
-        In this case, it is possible to have multiple HTML templates. If a localized template (e.g.,
-        <code>Home_jp.html</code> for a Japanese locale) exists, it will be used as appropriate.
-      </p>
-      
-      <p>
-        Page and component <em>specifications</em> are never localized, just <em>templates</em>.
-      </p>
-      
-      <p>
-        It is a good idea to make use of declared components, rather than implicit components, when
-        using localized templates ... it reduces duplication in the templates.
-      </p>
-    </section>
+    Licensed under the Apache License, Version 2.0 (the "License");
+    you may not use this file except in compliance with the License.
+    You may obtain a copy of the License at
     
-    <section name="Template encoding">
-      
-      
-      <p>
-        Like <a href="#localization.component-catalog.encoding">message catalogs</a>,
-        each template may be written in a different character set.  
-      </p>
-      
-        <p>
-          For each localization of the base key (<code>org.apache.tapestry.template-encoding</code>, a search of the following locations takes place.
-        </p>
-        <ul>
-          <li>The page or component specification.</li>
-          <li>The namespace specification for the namespace containing the page or component.</li>
-          <li>The <a href="configuration.html#configuration.search-path">application property search path</a>
-</li>
-        </ul>
-    </section>
+    http://www.apache.org/licenses/LICENSE-2.0
     
-    <section name="Using the message: binding prefix">
-      
-      
-      <p>
-        When specifying a parameter binding, the <code>message:</code> prefix
-        is used to reference a localized message key.  For example:
-      </p>
-      
-<source xml:space="preserve">
+    Unless required by applicable law or agreed to in writing, software
+    distributed under the License is distributed on an "AS IS" BASIS,
+    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+    See the License for the specific language governing permissions and
+    limitations under the License.
+-->
+<document>
+    <properties>
+        <title>Localization</title>
+    </properties>
+    <body>
+        <section name="Localization">
+            <p>
+                Proper localization is a pervasive aspect of web application development. Supporting
+                users from different countries, with different languages, can be a tricky
+                proposition ... it is more than just text that must be localized, but more subtle
+                aspects of the application such as date and currency formats. It is also more than
+                text ... in some cases, a localized application will want to change images or even
+                color schemes.
+            </p>
+            <p>Localization support in Tapestry is likewise pervasive.</p>
+            <section name="Component Message Catalogs">
+
+                <p>
+                    The most fundamental aspect of localization in Tapestry are component message
+                    catalogs (remember that pages are components too). A message catalog is a
+                    mapping from a logical key (that may appear in Java code or in OGNL expressions)
+                    to a literal string. Tapestry message catalogs are similar to Java's
+                    ResourceBundle class, except there is more flexibility in the character set of
+                    the files, and the location of the files.
+                </p>
+                <p>
+                    Each component
+                    <em>may</em>
+                    have a message catalog, consisting of a set of localized message properties
+                    files.
+                </p>
+                <p>
+                    These files are stored with the page or component specification file. They are
+                    named the same as the specification file, but with a different extension
+                    (".properties" instead of ".jwc" or ".page").
+                </p>
+                <p>
+                    In addition, this is a
+                    <em>set</em>
+                    of files; a locale string may be inserted just before the extension. For
+                    example,
+                    <code>WEB-INF/Home_fr.properties</code>
+                    to contain the French language localization of the keys.
+                </p>
+                <p>
+                    As with Java's ResourceBundle, resolution of a key to a message starts with the
+                    most
+                    <em>specific</em>
+                    properties file. Any key not found there will be searched for in less specific
+                    files. For example, the search path could be
+                    <code>Home_fr_BE.properties</code>
+                    ,
+                    <code>Home_fr.properties</code>
+                    ,
+                    <code>Home.properties</code>
+                    .
+                </p>
+                <p>
+                    If a properties file does not exist, that's perfectly ok, the search will
+                    continue.
+                </p>
+                <p>
+                    When a key can not be found even in the most general properties file, a search
+                    occurs in the
+                    <a href="#localization.namespace">namespace</a>
+                    . In this way, very common strings can be stored and localized once, and used
+                    throughout a library or application.
+                </p>
+                <p>
+                    We'll describe how to use the message catalog shortly, but first some notes on
+                    how the message catalogs are read.
+                </p>
+                <subsection name="Properties file encoding">
+
+                    <p>
+                        For Java's ResourceBundle, the properties files must be in UTF-8 character
+                        set. This can be problematic, as in non-western languages it is necessary to
+                        use Java's native2ascii tool to convert from non-native files into an ASCII
+                        encoding of UTF-8.
+                    </p>
+                    <p>
+                        Tapestry can read properties files in alternate character sets, but must be
+                        told what character set the file is encoded in (internally, the contents
+                        must be converted into standard multi-byte Unicode).
+                    </p>
+                    <p>
+                        This is accomplished by providing some metadata inside the component (or
+                        page) specification. Metadata is specified using the
+                        <a href="spec.html#spec.meta">&lt;meta&gt;</a>
+                        element.
+                    </p>
+                    <p>
+                        The resolution of the character set is somewhat complicated; it is possible
+                        that each properties file will use a different character set. At the same
+                        time, repetition is bad ... therefore it is possible to specify some of this
+                        information in the namespace meta data (in the containing application or
+                        library specification) so that it can apply to all pages and components
+                        within the namespace.
+                    </p>
+
+                    <p>
+                        The basic meta-data property name searched for is
+                        <code>org.apache.tapestry.messages-encoding</code>
+                        . The value for this name is the name of the charset for the properties
+                        file.
+                    </p>
+
+                    <p>
+                        However, the base name is modified to reflect the locale for the file being
+                        read; the locale string is appended to the key, thus
+                        <code>org.apache.tapestry.messages-encoding_fr</code>
+                        will define the character set for the file
+                        <code>WEB-INF/Home_fr.properties</code>
+                    </p>
+
+                    <p>
+                        For each localization of the base property name, a search of the following
+                        locations takes place.
+                    </p>
+                    <ul>
+                        <li>The page or component specification.</li>
+                        <li>
+                            The namespace (library or application) specification for the namespace
+                            containing the page or component.
+                        </li>
+                        <li>
+                            The
+                            <a href="configuration.html#configuration.global-property-source">
+                                global property source
+                            </a>
+                            .
+                        </li>
+                    </ul>
+
+                    <p>
+                        Because localization of templates is similar to localization of message
+                        properties files, a second search occurs if the search for (variations of)
+                        <code>org.apache.tapestry.messages-encoding</code>
+                        fails; this time for
+                        <code>org.apache.tapestry.template-encoding</code>
+                        occurs (again, with variations for each locale).
+                    </p>
+
+                    <p>
+                        The ultimate default for encoding character set is ISO-8859-1; in other
+                        words, the same behavior as reading an ordinary Java ResourceBundle.
+                    </p>
+
+                </subsection>
+            </section>
+            <section name="Missing keys">
+
+
+                <p>
+                    While developing, you may occasionally reference a key that does not exist.
+                    Rather than fail with an exception, Tapestry will fabricate a missing key value.
+                    This is the key, converted to upper-case, and surrounded with brackets. For
+                    example,
+                    <code>[A-MISSING-KEY]</code>
+                    . This allows missing key values to stand out an demand to be fixed, without
+                    completely subverting your application.
+                </p>
+
+            </section><!-- localization.missing-keys -->
+            <section name="Namespace message catalogs">
+
+
+                <p>
+                    It is very likely that you'll have a number of strings that are used, and
+                    re-used, throughout your application. Rather than duplicate the same message
+                    keys and localized values in all your page and component message catalogs, you
+                    can put these into your
+                    <em>namespace</em>
+                    catalog.
+                </p>
+
+                <p>
+                    Each page and component is part of a
+                    <code>namespace</code>
+                    , identified by a library specification or component specification.
+                </p>
+
+                <p>
+                    The specification may also have a message catalog; for instance, for
+                    <code>WEB-INF/myapp.application</code>
+                    , the files would be named
+                    <code>WEB-INF/myapp.properties</code>
+                    , etc. Again, the name of the file is based on the servlet name ("myapp").
+                </p>
+
+                <p>
+                    Very simple applications may not have an application specification, but may
+                    still have properties, just as if the application specification existed.
+                </p>
+
+            </section><!-- localization.namespace -->
+            <!-- localization.component-catalog -->
+            <section name="Template text localization">
+
+                <p>
+                    As described in
+                    <a href="template.html#template.directives.l10n">
+                        the discussion of Tapestry templates
+                    </a>
+                    , static text in an HTML template can be enclosed in a specialized &lt;span&gt;
+                    tag.
+                </p>
+
+            </section>
+
+            <section name="Localized templates">
+
+
+                <p>
+                    In some cases, the entire layout of a page (or component) must change due to
+                    locale. For example, because of differences between western languages (which
+                    read left to right) and many eastern languages (which read right to left).
+                </p>
+
+                <p>
+                    In this case, it is possible to have multiple HTML templates. If a localized
+                    template (e.g.,
+                    <code>Home_jp.html</code>
+                    for a Japanese locale) exists, it will be used as appropriate.
+                </p>
+
+                <p>
+                    Page and component
+                    <em>specifications</em>
+                    are never localized, just
+                    <em>templates</em>
+                    .
+                </p>
+
+                <p>
+                    It is a good idea to make use of declared components, rather than implicit
+                    components, when using localized templates ... it reduces duplication in the
+                    templates.
+                </p>
+            </section>
+
+            <section name="Template encoding">
+
+
+                <p>
+                    Like
+                    <a href="#localization.component-catalog.encoding">message catalogs</a>
+                    , each template may be written in a different character set.
+                </p>
+
+                <p>
+                    For each localization of the base key (
+                    <code>org.apache.tapestry.template-encoding</code>
+                    , a search of the following locations takes place.
+                </p>
+                <ul>
+                    <li>The page or component specification.</li>
+                    <li>
+                        The namespace specification for the namespace containing the page or
+                        component.
+                    </li>
+                    <li>
+                        The
+                        <a href="configuration.html#configuration.search-path">
+                            application property search path
+                        </a>
+                    </li>
+                </ul>
+            </section>
+
+            <section name="Using the message: binding prefix">
+
+
+                <p>
+                    When specifying a parameter binding, the
+                    <code>message:</code>
+                    prefix is used to reference a localized message key. For example:
+                </p>
+
+                <source xml:space="preserve">
 &lt;html jwcid="@<a href="site:Shell">Shell</a>" title="message:page-title"&gt;
  . . .
 &lt;/html&gt;
-</source>      
-      
-    </section>
-    
-    <section name="Localization of Assets">
-      
-      
-      <p>
-Assets may also be localized.  Classpath and context assets will  automatically search for a
-locale-specific match (this is very similar to how localized templates work).
-      </p>
-    </section>  <!-- localization.assets -->
-    
-    <section name="Formatting messages">
-      
-      
-<p>
-Messages may contain <em>arguments</em>, strings of the form <code>{0}</code> (or
-some other number). The argument are handled exactly the same as with Java's MessageFormat
-class (in fact, under the covers, MessageFormat does the work).
-</p>      
-
-<p>
-Components include a <code>messages</code> property for accessing localized messages.
-This property is of type Messages, and includes two methods:
-</p>
-
-<ul>
-  <li>
-<code>getMessage()</code> takes a string parameter and returns a localized message</li>
-  <li>
-<code>format()</code> takes a string parameter (the key) and then takes a number of
-    additional parameters as arguments.  The arguments are just objects.  If you have more
-    than three arguments, then specify them as an object array.</li>
-</ul>
-
-<p>
-It is common to format messages using OGNL expessions, i.e.:
-</p>
+</source>
 
-<source xml:space="preserve">
+            </section>
+
+            <section name="Localization of Assets">
+
+
+                <p>
+                    Assets may also be localized. Classpath and context assets will automatically
+                    search for a locale-specific match (this is very similar to how localized
+                    templates work).
+                </p>
+            </section><!-- localization.assets -->
+
+            <section name="Formatting messages">
+
+
+                <p>
+                    Messages may contain
+                    <em>arguments</em>
+                    , strings of the form
+                    <code>{0}</code>
+                    (or some other number). The argument are handled exactly the same as with Java's
+                    MessageFormat class (in fact, under the covers, MessageFormat does the work).
+                </p>
+
+                <p>
+                    Components include a
+                    <code>messages</code>
+                    property for accessing localized messages. This property is of type Messages,
+                    and includes two methods:
+                </p>
+
+                <ul>
+                    <li>
+                        <code>getMessage()</code>
+                        takes a string parameter and returns a localized message
+                    </li>
+                    <li>
+                        <code>format()</code>
+                        takes a string parameter (the key) and then takes a number of additional
+                        parameters as arguments. The arguments are just objects. If you have more
+                        than three arguments, then specify them as an object array.
+                    </li>
+                </ul>
+
+                <p>It is common to format messages using OGNL expessions, i.e.:</p>
+
+                <source xml:space="preserve">
 &lt;span jwcid="@<a href="site:Insert">Insert</a>" value="ognl:messages.format('billing-info', amountDue)"/&gt;
 </source>
 
-<p>
-The above example would get the amountDue property and pass it in as argument 0 to the message
-format retrieved from the message catalog as key 'billing-info'.
-</p>
-      
-    </section>
-    
-<section name="Changing the locale">
-   
-  
-<p>
-In order to change the locale, you must obtain the <a href="../tapestry-framework/apidocs/org/apache/tapestry/IEngine.html">IEngine</a> and invoke <code>setLocale()</code> on it.
-This will change the value stored in the engine (which is used when loading new pages), and:
-</p>
-
-<ul>
-  <li>Update the hivemind.ThreadLocale service, allowing localized messages from services to be generated
-    in the correct locale</li>
-  <li>Cause an HTTP Cookie to be added to the request so that future requests from the same client
-    will be in the same locale</li>
-</ul>
-
-<p>
-  Changing the locale <a href="#localization.engine-locale">does not affect any pages loaded
-    in the current request.</a>
-</p>
- 
-  
-</section>    
-    
-    <section name="Engine locale vs. page locale">
-      
-      
-<p>
-When pages are created, or obtained from the page pool, the engine's locale is
-taken into account.  Pages are obtained when they are used by a service,
-or when accessed via <a href="../tapestry-framework/apidocs/org/apache/tapestry/IRequestCycle.html">IRequestCycle</a>.getPage().
-</p>      
-      
-<p>
-A page is loaded for a particular locale, and the page's locale never changes.
-This is because of the degree to which localization creeps into the properties
-of the page and the components within the page.
-</p>      
-
-<p>
-Additionally, once a page  is loaded during a request cycle, it is kept
-for the duration of the cycle ... even if the engine locale changes.
-</p>
-
-<p>
-If you have a listener method on a page that changes the engine's locale, it is necessary to activate a <em>different</em>
-page to render the response.  This new page will be loaded in the new locale.
-</p>
-
-<p>
-<strong>Note:</strong>
-<br/>
-This may be addressed somewhat in Tapestry 4.0.  Two options are possible: a service for
-changing the locale before rendering a page, and a way to force Tapestry to re-load a page, in a new
-locale.
-</p>
-      
-    </section>
-    
-<section name="Limiting accepted locales">
-  
-  
-<p>
-By default, Tapestry accepts incoming locales (as specified in the request HTTP header) as-is. The requested
-locale is used as-is.  This has some implications, primarily in terms of resource usage.  
-</p>  
-
-<p>
-Imagine an application that is being accessed by users in the US, the UK and in Canada. The incoming request
-locales will be "en_US", "en_UK" and "en_CA" (respectively). However, it is likely that you will only have
-created a single localization, for English in general (locale "en").  Despite this, there will be several different
-versions of each page in the page pool: one for each of the above locales, even though they will be functionally identical.
-</p>
-
-<p>
-Ideally, what we want is to limit incoming requests so that all of the listed locales ("en_US", "en_UK" and "en_CA") will
-be 'filtered down' to just "en".
-</p>
-
-<p>
-That functionality is controlled by the org.apache.tapestry.accepted-locales <a href="configuration.html#configuration.properties">configuration property</a>. By setting
-this property to a comma-seperated list of local names, incoming requests will be converted
-to the closest match.  For example, the the property could be configured to "en,fr,de" to support English, French and German.
-</p>
-
-<p>
-Matching takes place by stripping off "terms" (the locale variant, then the locale country code) from the locale name.  So "en_US" would be stripped to "en" (which would match).
-When no match can be found, the <em>first</em> locale in the list is treated as the default.  In the prior example, Russian users
-would be matched to the "en" locale.
-</p>
-
-</section>    
-  </body>
+                <p>
+                    The above example would get the amountDue property and pass it in as argument 0
+                    to the message format retrieved from the message catalog as key 'billing-info'.
+                </p>
+
+            </section>
+
+            <section name="Changing the locale">
+
+
+                <p>
+                    In order to change the locale, you must obtain the
+                    <a href="../tapestry-framework/apidocs/org/apache/tapestry/IEngine.html">
+                        IEngine
+                    </a>
+                    and invoke
+                    <code>setLocale()</code>
+                    on it. This will change the value stored in the engine (which is used when
+                    loading new pages), and:
+                </p>
+
+                <ul>
+                    <li>
+                        Update the hivemind.ThreadLocale service, allowing localized messages from
+                        services to be generated in the correct locale
+                    </li>
+                    <li>
+                        Cause an HTTP Cookie to be added to the request so that future requests from
+                        the same client will be in the same locale
+                    </li>
+                </ul>
+
+                <p>
+                    Changing the locale
+                    <a href="#localization.engine-locale">
+                        does not affect any pages loaded in the current request.
+                    </a>
+                </p>
+
+
+            </section>
+
+            <section name="Engine locale vs. page locale">
+
+
+                <p>
+                    When pages are created, or obtained from the page pool, the engine's locale is
+                    taken into account. Pages are obtained when they are used by a service, or when
+                    accessed via
+                    <a
+                        href="../tapestry-framework/apidocs/org/apache/tapestry/IRequestCycle.html">
+                        IRequestCycle
+                    </a>
+                    .getPage().
+                </p>
+
+                <p>
+                    A page is loaded for a particular locale, and the page's locale never changes.
+                    This is because of the degree to which localization creeps into the properties
+                    of the page and the components within the page.
+                </p>
+
+                <p>
+                    Additionally, once a page is loaded during a request cycle, it is kept for the
+                    duration of the cycle ... even if the engine locale changes.
+                </p>
+
+                <p>
+                    If you have a listener method on a page that changes the engine's locale, it is
+                    necessary to activate a
+                    <em>different</em>
+                    page to render the response. This new page will be loaded in the new locale.
+                </p>
+
+                <span class="info">
+                    <strong>Note:</strong>
+                    <p>
+                        This may be addressed somewhat in Tapestry 4.0. Two options are possible: a
+                        service for changing the locale before rendering a page, and a way to force
+                        Tapestry to re-load a page, in a new locale.
+                    </p>
+                </span>
+
+            </section>
+
+            <section name="Limiting accepted locales">
+
+
+                <p>
+                    By default, Tapestry accepts incoming locales (as specified in the request HTTP
+                    header) as-is. The requested locale is used as-is. This has some implications,
+                    primarily in terms of resource usage.
+                </p>
+
+                <p>
+                    Imagine an application that is being accessed by users in the US, the UK and in
+                    Canada. The incoming request locales will be "en_US", "en_UK" and "en_CA"
+                    (respectively). However, it is likely that you will only have created a single
+                    localization, for English in general (locale "en"). Despite this, there will be
+                    several different versions of each page in the page pool: one for each of the
+                    above locales, even though they will be functionally identical.
+                </p>
+
+                <p>
+                    Ideally, what we want is to limit incoming requests so that all of the listed
+                    locales ("en_US", "en_UK" and "en_CA") will be 'filtered down' to just "en".
+                </p>
+
+                <p>
+                    That functionality is controlled by the org.apache.tapestry.accepted-locales
+                    <a href="configuration.html#configuration.properties">configuration property</a>
+                    . By setting this property to a comma-seperated list of local names, incoming
+                    requests will be converted to the closest match. For example, the the property
+                    could be configured to "en,fr,de" to support English, French and German.
+                </p>
+
+                <p>
+                    Matching takes place by stripping off "terms" (the locale variant, then the
+                    locale country code) from the locale name. So "en_US" would be stripped to "en"
+                    (which would match). When no match can be found, the
+                    <em>first</em>
+                    locale in the list is treated as the default. In the prior example, Russian
+                    users would be matched to the "en" locale.
+                </p>
+
+            </section>
+        </section>
+    </body>
 </document>

Modified: tapestry/tapestry4/trunk/src/site/xdoc/UsersGuide/page-class.xml
URL: http://svn.apache.org/viewvc/tapestry/tapestry4/trunk/src/site/xdoc/UsersGuide/page-class.xml?rev=420925&r1=420924&r2=420925&view=diff
==============================================================================
--- tapestry/tapestry4/trunk/src/site/xdoc/UsersGuide/page-class.xml (original)
+++ tapestry/tapestry4/trunk/src/site/xdoc/UsersGuide/page-class.xml Tue Jul 11 09:54:16 2006
@@ -1,116 +1,159 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!-- 
-   Copyright 2005 The Apache Software Foundation
-
-   Licensed under the Apache License, Version 2.0 (the "License");
-   you may not use this file except in compliance with the License.
-   You may obtain a copy of the License at
-
-       http://www.apache.org/licenses/LICENSE-2.0
-
-   Unless required by applicable law or agreed to in writing, software
-   distributed under the License is distributed on an "AS IS" BASIS,
-   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-   See the License for the specific language governing permissions and
-   limitations under the License.
+    Copyright 2005 The Apache Software Foundation
+    
+    Licensed under the Apache License, Version 2.0 (the "License");
+    you may not use this file except in compliance with the License.
+    You may obtain a copy of the License at
+    
+    http://www.apache.org/licenses/LICENSE-2.0
+    
+    Unless required by applicable law or agreed to in writing, software
+    distributed under the License is distributed on an "AS IS" BASIS,
+    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+    See the License for the specific language governing permissions and
+    limitations under the License.
 -->
 <document>
-<properties>
-<title>Determining the Page Class</title>
-</properties>
-<body>
-<p>
-  When it comes time for Tapestry to instantiate a page, it must identify the Java class
-  to instantiate.
-</p>
-
-<p>
-Tapestry pages implement the <a href="../tapestry-framework/apidocs/org/apache/tapestry/IPage.html">IPage</a> interface.  Because this is a large interface,
-you will typically extends the <a href="../tapestry-framework/apidocs/org/apache/tapestry/html/BasePage.html">BasePage</a> base class (for HTML pages).
-</p>
-
-<p>
-Typically, you will identify the page class within the page's specification, using
-the <a href="spec.html#spec.page-specification">&lt;page-specification&gt;</a> element's class attribute.
-</p>
-
-<p>
-In many cases, however, the page specification is optional.  Alternately, the class
-attribute may be omitted from the page specification.  Tapestry takes the following steps
-to find the class for a page:
-</p>
-
-<ul>
-  <li>As indicated in the page specification</li>
-  <li>By searching the packages listed in the application specification (more below)</li>
-  <li>The application specification's org.apache.tapestry.default-page-class property</li>
-  <li>The global property org.apache.tapestry.default-page-class</li>
-</ul>
-
-<p>
-The most useful of these is the second option, to search.  For this step,
-Tapestry looks in the application specification
-for the org.apache.tapestry.page-class-packages <a href="spec.html#spec.meta">&lt;meta&gt;</a> property. This
-is a comma-seperated list of package names to search.  The list of packages is
-optional, and the default Java package is searched last.
-</p>
-
-<p>
-Also, for this search, the page name is converted into a partial class name. For pages
-inside folders, the folder names are part of the package name, so page name
-<code>admin/EditUser</code> will be become <code>admin.EditUser</code>.
-</p>
-
-<p>
-So, if the prefix list is <code>org.example.pages</code>, then Tapestry will search
-for <code>org.example.pages.admin.EditUser</code>, then
-<code>admin.EditUser</code> (that is, in the default package).
-</p>
-
-<p>
-Only if those searches fail to locate a class  does Tapestry continue to the next steps, using
-default page class names in the application specification and beyond.
-</p>
-
-<p>
-<strong>Note:</strong>
-<br/>
-These steps are specified in the
-<a href="../tapestry/hivedocs/config/tapestry.page.PageClassProviderChain.html">tapestry.page.PageClassProviderChain</a>
-configuration point.
-</p>
-
-<p>
-For simplicity, we described the search for application pages. For pages within a library, the process
-is the same, but it is the library's specification which is searched for the list of packages,
-and later, for the default page class name.
-</p>
-
-<section name="Component Classes">
-  
-  
-<p>
-A similar search occurs for components (again, with the express desire that the class attribute of the
-<a href="spec.html#spec.component-specification">&lt;component-specification&gt;</a> <em>not</em> be used).  
-</p>
-
-<ul>
-  <li>As defined by the component specification</li>
-  <li>In any package defined by the containing namespace's org.apache.tapestry.component-class-packages
-    meta data property (if any)</li>
-  <li>In the default package</li>
-  <li>
-<a href="../tapestry-framework/apidocs/org/apache/tapestry/BaseComponent.html">BaseComponent</a> is the final default</li>
-</ul>
-
-<p>
-<strong>Note:</strong>
-<br/>
-These steps are specified in the
-<a href="../tapestry/hivedocs/config/tapestry.page.ComponentClassProviderChain.html">tapestry.page.ComponentClassProviderChain</a>
-configuration point.
-</p>
-</section>
-
-</body>
+    <properties>
+        <title>Determining the Page Class</title>
+    </properties>
+    <body>
+    
+        <section name="Determining the Page Class">
+            <p>
+                When it comes time for Tapestry to instantiate a page, it must identify the Java
+                class to instantiate.
+            </p>
+
+            <p>
+                Tapestry pages implement the
+                <a href="../tapestry-framework/apidocs/org/apache/tapestry/IPage.html">IPage</a>
+                interface. Because this is a large interface, you will typically extends the
+                <a href="../tapestry-framework/apidocs/org/apache/tapestry/html/BasePage.html">
+                    BasePage
+                </a>
+                base class (for HTML pages).
+            </p>
+
+            <p>
+                Typically, you will identify the page class within the page's specification, using
+                the
+                <a href="spec.html#spec.page-specification">&lt;page-specification&gt;</a>
+                element's class attribute.
+            </p>
+
+            <p>
+                In many cases, however, the page specification is optional. Alternately, the class
+                attribute may be omitted from the page specification. Tapestry takes the following
+                steps to find the class for a page:
+            </p>
+
+            <ul>
+                <li>As indicated in the page specification</li>
+                <li>
+                    By searching the packages listed in the application specification (more below)
+                </li>
+                <li>
+                    The application specification's org.apache.tapestry.default-page-class property
+                </li>
+                <li>The global property org.apache.tapestry.default-page-class</li>
+            </ul>
+
+            <p>
+                The most useful of these is the second option, to search. For this step, Tapestry
+                looks in the application specification for the
+                org.apache.tapestry.page-class-packages
+                <a href="spec.html#spec.meta">&lt;meta&gt;</a>
+                property. This is a comma-seperated list of package names to search. The list of
+                packages is optional, and the default Java package is searched last.
+            </p>
+
+            <p>
+                Also, for this search, the page name is converted into a partial class name. For
+                pages inside folders, the folder names are part of the package name, so page name
+                <code>admin/EditUser</code>
+                will be become
+                <code>admin.EditUser</code>
+                .
+            </p>
+
+            <p>
+                So, if the prefix list is
+                <code>org.example.pages</code>
+                , then Tapestry will search for
+                <code>org.example.pages.admin.EditUser</code>
+                , then
+                <code>admin.EditUser</code>
+                (that is, in the default package).
+            </p>
+
+            <p>
+                Only if those searches fail to locate a class does Tapestry continue to the next
+                steps, using default page class names in the application specification and beyond.
+            </p>
+
+            <span class="info">
+                <strong>Note:</strong>
+                <p>
+                    These steps are specified in the
+                    <a
+                        href="../tapestry/hivedocs/config/tapestry.page.PageClassProviderChain.html">
+                        tapestry.page.PageClassProviderChain
+                    </a>
+                    configuration point.
+                </p>
+            </span>
+
+            <p>
+                For simplicity, we described the search for application pages. For pages within a
+                library, the process is the same, but it is the library's specification which is
+                searched for the list of packages, and later, for the default page class name.
+            </p>
+
+            <section name="Component Classes">
+
+
+                <p>
+                    A similar search occurs for components (again, with the express desire that the
+                    class attribute of the
+                    <a href="spec.html#spec.component-specification">
+                        &lt;component-specification&gt;
+                    </a>
+                    <em>not</em>
+                    be used).
+                </p>
+
+                <ul>
+                    <li>As defined by the component specification</li>
+                    <li>
+                        In any package defined by the containing namespace's
+                        org.apache.tapestry.component-class-packages meta data property (if any)
+                    </li>
+                    <li>In the default package</li>
+                    <li>
+                        <a
+                            href="../tapestry-framework/apidocs/org/apache/tapestry/BaseComponent.html">
+                            BaseComponent
+                        </a>
+                        is the final default
+                    </li>
+                </ul>
+
+                <span class="info">
+                    <strong>Note:</strong>
+                    <p>
+                        These steps are specified in the
+                        <a
+                            href="../tapestry/hivedocs/config/tapestry.page.ComponentClassProviderChain.html">
+                            tapestry.page.ComponentClassProviderChain
+                        </a>
+                        configuration point.
+                    </p>
+                </span>
+            </section>
+            
+        </section>
+        
+    </body>
 </document>



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