How to use servlet filter to forward request and change body data request from formdataparam to formparam?

I'm working on a web application (Java) server side and I want to use servlet filter to filter client requests. I created a class that implements Filter, like this:

public class ServletFilter implements Filter{
  private ServletContext context;

  @Override
  public void init(FilterConfig filterConfig) throws ServletException {
    ...
  }

  @Override
  public void destroy(){
    ...
  }

  @Override
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain){
    HttpServletRequest req = (HttpServletRequest) request;
    HttpServletResponse resp = (HttpServletResponse) response;
    
    if(req.getContentType() != null && req.getContentType().toLowerCase().contains("multipart/form-data")){
      RequestDispatcher rd = request.getRequestDispatcher("servlet/called");
      rd.forward(request, response);
    }
    chain.doFilter(request,response);
  }

}

In this case, there is only one filter, so when request arrived, it is intercepted from filter and if the Content-Type of the request is multipart/form-data, call a specific servlet via RequestDispatcher. It works.

Then, since there are no other filters, the command chain.doFilter(request,response) call myMethod (the method which is called from client request).

myMethod like as:

@POST
@Path("example1")
@Consumes("application/x-www-form-urlencoded")
public void myMethod(@FormParam("element") String entity){
  ...
}

The problem is that this method is never called from filter. But, if client make a request for otherMethod, like this:

@POST
@Path("example2")
@Consumes("multipart/form-data")
public void otherMethod(@FormDataParam("element") String entity){
  ...
}

the request is forwarded and the method is called.

myMethod and otherMethod belong to the same class, that has annotation: @Path(value="ws").

This is my web.xml:

<filter>
  <filter-name>FilterServlet</filter-name>
  <filter-class>packages.servlets.FilterServlet</filter-class>
</filter>
    
<filter-mapping>
  <filter-name>FilterServlet</filter-name>
  <url-pattern>/ws/*</url-pattern>
  <dispatcher>REQUEST</dispatcher>
</filter-mapping>

Body data are sent as FormDataParam in client request.

I think the problem is represented by different media type (multipart or form-urlencoded) consumed by webservices. So, can I convert Content-Type of the request from multipart to form-urlencoded? How can I solve it? What am I doing wrong?

Thanks!