How to Guarantee UTF-8 Encoding Throughout a Java Web Application?

How to Ensure UTF-8 Encoding in Java Web Applications

To enable UTF-8 encoding in your Java webapp, follow these steps:

1. Configure Tomcat's server.xml

Add the following line to enable UTF-8 encoding for URL (GET request) parameters:

<Connector port="8080" ... URIEncoding="UTF-8" ... />

2. Implement a Character Set Filter

Define a filter to force the webapp to handle all requests and responses as UTF-8 encoded:

import javax.servlet.*;

public class CharsetFilter implements Filter {

    private String encoding = "UTF-8";

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain next) throws ServletException, IOException {
        request.setCharacterEncoding(encoding);
        response.setContentType("text/html; charset=UTF-8");
        response.setCharacterEncoding("UTF-8");
        next.doFilter(request, response);
    }
}

3. Add the Filter to web.xml

Register the filter in the deployment descriptor:

<filter>
    <filter-name>CharsetFilter</filter-name>
    <filter-class>fi.foo.filters.CharsetFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>CharsetFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

4. Set JSP Page Encoding

Specify the page encoding in web.xml:

<jsp-config>
    <jsp-property-group>
        <url-pattern>*.jsp</url-pattern>
        <page-encoding>UTF-8</page-encoding>
    </jsp-property-group>
</jsp-config>

5. Use HTML-Meta Tags

Indicate the encoding used by HTML pages:

<meta http-equiv='Content-Type' content='text/html; charset=UTF-8' />

6. Configure JDBC Connection

Specify UTF-8 encoding for the database connection:

<Resource ... url="jdbc:mysql://localhost:3306/ID_development?useEncoding=true&amp;amp;characterEncoding=UTF-8"
... />

7. Create Tables with UTF-8 Collation

Ensure that all database tables have UTF-8 collation:

CREATE TABLE  `Users` (
    `id` int(10) unsigned NOT NULL auto_increment,
    `name` varchar(30) collate utf8_swedish_ci default NULL
    PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_swedish_ci ROW_FORMAT=DYNAMIC;

8. Check MySQL Server Configuration

Verify that the server is configured to use UTF-8 as the default character set:

[client]
default-character-set=utf8

[mysql]
default-character-set=utf8

Note:

While Cyrillic characters like "ж" can be handled through GET requests with UTF-8 encoding, characters like "ä" may be encoded in Latin1 (ISO-8859-1), causing inconsistencies.

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