專案生產環境往往會有這樣的需求，內網的生產環境的應用需要訪問網際網路上第三方的服務，但又出於安全考慮，不允許該生產機直接訪問網際網路，這時我們往往通過代理方式來實現網外服務的訪問：我們可以在可訪問網際網路的機器上，使用nginx或者apache做代理，然後通過httpClient的代理機制實現。

以下是httpClient使用代理的程式碼片段：

        String document = objectMapper.writeValueAsString(requestObj);
        HttpClient httpClient = clientBuilder.build();
        // 依次是代理地址，代理埠號，協議型別  
 

        HttpHost proxy = new HttpHost(代理地址, 代理埠, "http");
        RequestConfig config = RequestConfig.custom().setProxy(proxy).build();  
        HttpPost httpPost = new HttpPost(url);
        httpPost.setEntity(new StringEntity(document, "UTF-8"));
        httpPost.addHeader("Content-Type", "application/xml;charset=utf-8"
 
);
        httpPost.setConfig(config); 

        CloseableHttpResponse response = null;
        try{
            response = (CloseableHttpResponse)httpClient.execute(target,httpPost);
        }finally{
            if(response != null){
                response.close();
            }
            if(httpPost != null
 
){
                httpPost.abort();
            }
        }