java - Tomcat CORS filter

Question

I want to enable tomcat CORS filter, i added this to web.xml:

<filter>
    <filter-name>CorsFilter</filter-name>
    <filter-class>org.apache.catalina.filters.CorsFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>CorsFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

But it doesn't work. I tried with a custom filter:

<filter>
    <filter-name>SimpleCORSFilter</filter-name>
    <filter-class>com.common.SimpleCORSFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>SimpleCORSFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

With this Class:

public class SimpleCORSFilter implements Filter {

    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
        HttpServletResponse response = (HttpServletResponse) res;
        response.setHeader("Access-Control-Allow-Origin", "*");
        response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");
        response.setHeader("Access-Control-Max-Age", "3600");
        response.setHeader("Access-Control-Allow-Headers", "x-requested-with");
        chain.doFilter(req, res);
    }
}

And this well works, can you tell me why? I don't know if it is important but I'm usign Spring Framework.

Answer 1

The filter org.apache.catalina.filters.CorsFilter seek first a header in the request: Origin. If this header does not exist, the filter does not add any header in the response. Perhaps for that reason does not work.

Additionally, in a POST request, look for the header Content-Type. Something similar happens to other methods. May you want to see the code of this filter. In another way, there is a flowchart: