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 it is thus configured with enctype="multipart/form-data". I configured the multipart upload in the web.xml file with the multipart-config element that is available since Servlet 3.0, combined with <bean id="multipartResolver" class="org.springframework.web.multipart.support.StandardServletMultipartResolver"/> in my spring configuration.

I also have Spring's org.springframework.web.filter.CharacterEncodingFilter configured.

The problem I have is that I cannot find a way to set the StandardServletMultipartResolver's default encoding to UTF-8, which often causes the contents of the textfields in the multipart form to be all garbled up.

Is there any way to fix this?

Thanks in advance.

web.xml config:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
                  http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
version="3.0">
<display-name>foo-web</display-name>
<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>
        WEB-INF\applicationContext.xml
    </param-value>
</context-param>
<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

<servlet>
    <servlet-name>foo</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <load-on-startup>0</load-on-startup>
    <multipart-config>
        <max-file-size>52428800</max-file-size>
        <file-size-threshold>5242880</file-size-threshold>
    </multipart-config>
</servlet>
<servlet-mapping>
    <servlet-name>foo</servlet-name>
    <url-pattern>/</url-pattern>
</servlet-mapping>

<filter>
    <filter-name>CharacterEncodingFilter</filter-name>
    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    <init-param>
        <param-name>encoding</param-name>
        <param-value>UTF-8</param-value>
    </init-param>
</filter>
<filter-mapping>
    <filter-name>CharacterEncodingFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

<filter>
    <filter-name>springSecurityFilterChain</filter-name>
    <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
</filter>
<filter-mapping>
    <filter-name>springSecurityFilterChain</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>
<welcome-file-list>
    <welcome-file>login</welcome-file>
</welcome-file-list>

Answer 1

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 2

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 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);
    }
}