How to change the character encoding for Servlet 3.0 Spring MVC multipart upload forms?

Question

I have a pretty simple JSP/Servlet 3.0/Spring MVC 3.1 application.

On one of my pages, I have multiple forms. One of these forms allows the user to upload a file and

Answer 1

I also had the problem with encoding when using the Servlet 3 API. After some research, I have found that there is a bug in Tomcat 7 which makes the parameters not to be read with the correct encoding under certain conditions. There is a work-around. First, you need to tell which encoding it actually is (if it is not default iso-8859-1):

request.setCharacterEncoding("UTF-8");

This is basically what the CharacterEncodingFilter in Spring does. Nothing strange so far. Now the trick. Call this:

request.getParameterNames()

Make sure this method is invoked before getParts(). If you are using Spring I guess you need to do this in a filter before the request ends up in Spring. The order which the methods are invoked are crucial.

Update: The Tomcat bug has been fixed in 7.0.41 onwards, so if you use a recent version of Tomcat you only need to set the character encoding to get correct result.

Answer 2

Since I found no way to set the default encoding using the StandardMultipartResolver, I dumped the servlet 3.0 config and went for the good old CommonsMultipartResolver.

I configured it like this in my spring servlet context:

<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <!-- one of the properties available; the maximum file size in bytes -->
    <property name="maxUploadSize" value="157286400" />
    <property name="maxInMemorySize" value="5242880"/>
    <property name="defaultEncoding" value="utf-8"/>
</bean>

In the end, there isn't much difference, since under the hood of the StandardMultipartResolver, it just delegates to CommonsMultipartResolver.

I actually find the servlet 3.0 approach more troublesome, since it requires configuration in both web.xml and your servlet context, and you lose the ability to set the default encoding.

Answer 3

I created my own multipart filter as holmis83 suggested, and worked fine

    public class MyMultiPartFilter extends MultipartFilter {

    Logger logger = LoggerFactory.getLogger(MyMultiPartFilter.class);

    @Override
    protected void doFilterInternal(HttpServletRequest request,
            HttpServletResponse response, FilterChain filterChain)
            throws ServletException, IOException {

        request.setCharacterEncoding("UTF-8");
        request.getParameterNames();

        super.doFilterInternal(request, response, filterChain);
    }
}