public static CharSequence getMimeType(HttpMessage message) {
        CharSequence contentTypeValue = message.headers().get(HttpHeaderNames.CONTENT_TYPE);
        if (contentTypeValue != null) {
            return getMimeType(contentTypeValue);
        } else {
            return null;
        }
    }
@Test
    public void testGetMimeType() {
        final String SIMPLE_CONTENT_TYPE = "text/html";
        final String NORMAL_CONTENT_TYPE = "text/html; charset=utf-8";

        HttpMessage message = new DefaultHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK);
        assertNull(HttpUtil.getMimeType(message));
        message.headers().set(HttpHeaderNames.CONTENT_TYPE, "");
        assertNull(HttpUtil.getMimeType(message));
        assertNull(HttpUtil.getMimeType(""));
        message.headers().set(HttpHeaderNames.CONTENT_TYPE, SIMPLE_CONTENT_TYPE);
        assertEquals("text/html", HttpUtil.getMimeType(message));
        assertEquals("text/html", HttpUtil.getMimeType(SIMPLE_CONTENT_TYPE));

        message.headers().set(HttpHeaderNames.CONTENT_TYPE, NORMAL_CONTENT_TYPE);
        assertEquals("text/html", HttpUtil.getMimeType(message));
        assertEquals("text/html", HttpUtil.getMimeType(NORMAL_CONTENT_TYPE));
    }