Question

I’m trying to setup CORS support in grails, and I’m using the following filter:

class CorsFilters {
    def filters = {
        all(controller:'*', action:'*') {
            before = {
                response.setHeader("Access-Control-Allow-Origin", "*")
            }
        }
    }
}

From testing, it looks like the response header is set properly for all requests, but when I make a request externally against localhost or some server available to me, I get the following error:

XMLHttpRequest cannot load http://server:8080. Origin http://jsbin.com is not allowed by Access-Control-Allow-Origin.

This live example works in my instance of Chrome, so I don’t know what could be happening here. In the requests that fail, I’m trying to hit tomcat directly.

What could be happening to cause this to fail?

Answer 1

It looks like Grails Filters, by default, run too late in the filter chain to be of use.

If you generate the web.xml template and add a filter beneath sitemesh, this works.

<filter>
    <filter-name>CORSFilter</filter-name>
    <filter-class>com.blah.CorsFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>CORSFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

and

class CorsFilter implements Filter {
    public void init(FilterConfig fConfig) throws ServletException { }

    public void destroy() { }

    public void doFilter(
            ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {

        ((HttpServletResponse) response).addHeader(
                "Access-Control-Allow-Origin", "*"
        )
        chain.doFilter(request, response)
    }
}