Choices in i18n web pages

Choices

To create a locale-aware set of web pages, the choices are

• Using a server such as Apache with type-maps
• Using a server such as Apache with multi-views
• Using a servlet only
• Using a JSP with scripting commands and expressions
• Using a JSP with standard tags and expression language
• Using a JSP with custom-built and standard tags and expression language
• Using a servlet and JSP (with scripting or tags)

Server negotiation using Apache type-map

• The server decides on the web page based on the Accept-language HTTP header
• It uses a type-map such as hello.var
• The URI's are interpreted as URLs relative to the map file; they must be on the same server (!), and they must refer to files to which the client would be granted access if they were to be requested directly.
• The directory structure can keep different language files in the same directory or in separate directories. Here we choose separate directories en and fr

  
        ..../hello.var
        ..../en/hello.html
        ..../fr/hello.html
        

• The English hello.html is
• The French hello.html is
• This can be tested here

Server negotiation using Apache multiviews

• A directory is marked for multiviews in the Apache configuration file e.g.

  
        <Directory "/home/httpd/html/i18n/webchoices/server-multiviews">
            Options MultiViews
        </Directory>
        

  or by having a file .htaccess in the directory with contents

  
        options MultiViews
        

• The directory contains files

  
        .htaccess
        hello.en.html
        hello.fr.html
        

• The pages are accessed by e.g server-multiviews/hello Note: no .html extension!

Apache server negotiation callng JSP/servlets?

• The above call HTML pages. Could they call servlets?
• The URLs appear to be relative to the current directory
• An Apache server couldn't call a Tomcat servlet because it would need an absolute URL
• If you integrate Tomcat into Apache (possible) then maybe it could be done

Server-side negotiation using servlets

• A servlet can examine the Accept-Language header and return a preferred locale or a list of all locales
• Given a locale, it could create a JSP name e.g. from hello and fr_FR it could create a name of fr_FR/hello.jsp
• If the JSP exists, then you can forward to it
• If the JSP does not exist, then an error is raised which normally returns a "404 not found". To remove this, you need to install an error handler, which will return say a page in a default locale
• The above program only handles the preferred locale, and does not fallback to less preferred ones. It should be possible to test if a JSP exists before calling it, but this needs use of ServletContext.getNamedDispatcher() which uses the name of a JSP
• The web.xml file in WEB-INF can map names to JSP compiled classes

  
      <servlet>
          <servlet-name>hello_fr_jsp</servlet-name>
          <servlet-class>org.apache.jsp.jsp.hello_fr_jsp</servlet-class>
      </servlet>
  
      <servlet-mapping>
          <servlet-name>fr_hello_jsp</servlet-name>
          <url-pattern>/jsp/fr/hello.jsp</url-pattern>
      </servlet-mapping>
        

• A servlet such as this should be able to call the JSP page
• It forwards to servlets by name ok, but doesn't seem to work for JSP names :-(

User negotiation

• The first page presents a choice of languages to continue.
• The language for this first page may be chosen by e.g. server-side negotiation or be multilingual
• e.g. the page firstpage.html may be
• This calls HTML pages in the en and fr directories - it could call servlets or JSP pages, and there could be different directory structures

Passing the locale in a session

• There may be a set of HTML pages/servlets/JSP for each locale
• This is high maintenance, and dosesn't encourage reuse of material from one locale to another
• An alternative may be to have a single set of pages where the locale is passed as a parameter to each of them
• This can work if the principal differences can be captured in resource bundles or localised using the locale (e.g. for dates)
• The single JSP page referenced would need to get the locale parameter and then could set its own locale for e.g. date formatting
• The JSP page could also store the locale in the session object if there are more pages in this session