Java 调用 webservice 接口，为什么这么慢

Java 调用 webservice 接口，为什么这么慢，有没有好的优化方案，本人目前改成 http 方式发 soap 消息调用，速度依旧很慢，维持在平均 100ms 下不来。 之前用 cxf 的 JaxWsDynamicClientFactory 速度更加慢，400ms 、500ms 都出现过。

这是现在使用 httpClient 的调用代码

public static String callWebSV(String urlWsdl,String soap,String soapAction){
        String result=null;
        try {
            CloseableHttpClient httpClient = HttpClients.createDefault();
            HttpPost httpPost = new HttpPost(urlWsdl);
            httpPost.setHeader("Content-Type", "text/xml;charset=UTF-8");
            httpPost.setHeader("SOAPAction", soapAction);
            InputStreamEntity entity = new InputStreamEntity(new ByteArrayInputStream(soap.getBytes()));
            httpPost.setEntity(entity);
            CloseableHttpResponse response = httpClient.execute( httpPost);
            if (response.getStatusLine().getStatusCode() == org.apache.http.HttpStatus.SC_OK) {
                HttpEntity responseEntity = response.getEntity();
                String back = EntityUtils.toString(responseEntity);
                //log.info("httpClient 返回 soap：" + back);
                result=parseResult(back);
                log.info("httpClient 返回结果：" + result);
            } else {
                log.error("HttpClinet 返回状态码：" + response.getStatusLine().getStatusCode());
            }
        } catch (Exception e) {
            log.error("调用错误：",e);
        }
        return result;
    }