Question

I face this problem. I have a filter that sets the character encoding of the request according to the filter’s config (for example, to UTF-8). This works with forms coded using the struts html:form tag. However, if I use the ordinary HTML form tag, the data are not encoded correctly.

This is the filter definition in the web.xml:

<filter>
    <filter-name>Encoding Filter</filter-name>
    <filter-class>EncodingFilter</filter-class>
    <init-param>
        <param-name>encoding</param-name>
        <param-value>UTF-8</param-value>
    </init-param>
 </filter>
 <filter-mapping>
    <filter-name>Encoding Filter</filter-name>
    <url-pattern>/*</url-pattern>
 </filter-mapping>

Here’s the filter :

public class EncodingFilter implements javax.servlet.Filter {
private String encoding;
public void init(FilterConfig filterConfig) throws ServletException {
    this.encoding = filterConfig.getInitParameter("encoding");
}
public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException, ServletException {
    request.setCharacterEncoding(encoding);
    filterChain.doFilter(request, response);
}
public void destroy() {
}

}

Answer 1

If you use a Struts tag <html:form> and omit the METHOD attribute it defaults to POST.
If you use a standard HTML <form> and omit the METHOD attribute it defaults to GET.

Tomcat will process your POST and GET parameters differently:

POST: your filter will be used. Note that you should really only set the request character encoding if it has not been specified by the client (your filter is always setting it to UTF-8). Tomcat comes with a filter SetCharacterEncodingFilter.java that does this.

GET: Tomcat will use ISO-8859-1 as the default character encoding. There are two ways to specify how GET parameters are interpreted:

• Set the URIEncoding attribute on the element in server.xml to something specific (e.g. URIEncoding=”UTF-8″).
• Set the useBodyEncodingForURI attribute on the element in server.xml to true. This will cause the Connector to use the request body’s encoding for GET parameters.

This is all in: http://wiki.apache.org/tomcat/FAQ/CharacterEncoding