public String getCharset() {
        String acceptCharset = getValue(HttpHeaderConsts.ACCEPT_CHARSET);
        if (acceptCharset == null) {
            String contentType = getValue(HttpHeaderConsts.CONTENT_TYPE);
            acceptCharset = StringUtils.isNotBlank(contentType) ? analysisCharset(contentType) : Constants.ENCODE;
        }
        return acceptCharset;
    }
@Test
    void testGetCharset() {
        Header header = Header.newInstance();
        assertEquals("UTF-8", header.getCharset());
        header.addParam(HttpHeaderConsts.ACCEPT_CHARSET, null);
        header.setContentType(MediaType.APPLICATION_JSON);
        assertEquals("UTF-8", header.getCharset());
        header.setContentType("application/json;charset=GBK");
        assertEquals("GBK", header.getCharset());
        header.setContentType("application/json");
        assertEquals("UTF-8", header.getCharset());
        header.setContentType("");
        assertEquals("UTF-8", header.getCharset());
    }