How to Properly Implement UTF-8 Encoding in a Java Web Application?

Getting UTF-8 Encoding in Java Webapps

Problem: Implementing UTF-8 encoding to support non-Latin characters for text and specific alphabets.

Environment:

• Development: Windows XP
• Production: Debian
• Database: MySQL 5.x
• Browsers: Firefox2, Opera 9.x, FF3, IE7, Google Chrome

Solution:

1. Configure Tomcat's server.xml:

   • Enable UTF-8 encoding for GET parameters:

2. CharsetFilter:

   • Force Java app to handle all requests and responses in UTF-8.

   • Add this filter to the web.xml:

     <filter>
       <filter-name>CharsetFilter</filter-name>
       <filter-class>fi.foo.filters.CharsetFilter</filter-class>
       <init-param>
         <param-name>requestEncoding</param-name>
         <param-value>UTF-8</param-value>
       </init-param>
     </filter>
     <filter-mapping>
       <filter-name>CharsetFilter</filter-name>
       <url-pattern>/*</url-pattern>
     </filter-mapping>

3. JSP Page Encoding:

   • Specify encoding for JSP pages in web.xml or add the following meta tag to each page:
     

4. JDBC Connection:

   • Use ?useEncoding=true&characterEncoding=UTF-8 in connection URL.

5. MySQL Database and Tables:

   • Create database and tables with DEFAULT CHARACTER SET=utf8 COLLATE=utf8_swedish_ci.

6. MySQL Server Configuration:

   • Set default-character-set=utf8 in my.ini (Windows) or my.cnf (Linux).

7. MySQL Procedures and Functions:

   • Specify UTF-8 character set explicitly, e.g.:
     CREATE FUNCTION ... RETURNS TEXT CHARACTER SET utf8

Handling GET Requests:

• By default, URLs are encoded in Latin1, causing problems with non-ASCII characters.
• To address this, define URL encoding in server.xml as UTF-8.
• Instruct browsers to read pages in UTF-8 using meta-tags and request headers.

UTF-8 vs. Latin1 in GET Requests:

• POST requests are encoded in UTF-8 by browsers.
• For GET requests, while the page is defined as UTF-8, some characters may still be encoded in Latin1. This results in mixed encoding, making it difficult for the webapp to handle request parameters correctly.

References:

• http://tagunov.tripod.com/i18n/i18n.html
• http://wiki.apache.org/tomcat/Tomcat/UTF-8
• http://java.sun.com/developer/technicalArticles/Intl/HTTPCharset/
• http://dev.mysql.com/doc/refman/5.0/en/charset-syntax.html
• http://cagan327.blogspot.com/2006/05/utf-8-encoding-fix-tomcat-jsp-etc.html
• http://cagan327.blogspot.com/2006/05/utf-8-encoding-fix-for-mysql-tomcat.html
• http://jeppesn.dk/utf-8.html
• http://www.nabble.com/request-parameters-mishandle-utf-8-encoding-td18720039.html
• http://www.utoronto.ca/webdocs/HTMLdocs/NewHTML/iso_table.html
• http://www.utf8-chartable.de/

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