前言： 当你处于公司内网无法对外网的接口访问，但是我们有一些第三方的接口处于外网，所以这个时候就需要配置代理服务器发出请求达到我们想要的目的。

通过代理服务器访问外网：
通过HttpClient官网提供的文档，发现HttpClient4.5的代理服务器做如下配置(附上HttpClient官网提供的文档的地址) --------官网地址

public static String postHttp(String url,String timestamp,String sign) {String result = "";CloseableHttpClient httpclient = null;CloseableHttpResponse res = null;try {HttpClientContext context = HttpClientContext.create();// 创建一个httpClient对象httpclient = HttpClients.createDefault();//登陆 从配置文件中读取url(也可以写成参数)HttpPost httpPost = new HttpPost(url); // 设置代理HttpHostHttpHost proxy = new HttpHost("proxy01.cnooc", 8080, "http");// 设置认证CredentialsProvider credsProvider = new BasicCredentialsProvider();// 添加代理用户认证-用户名和密码credsProvider.setCredentials(new AuthScope(proxy), new UsernamePasswordCredentials("****","****"));HttpClients.custom().setDefaultCredentialsProvider(credsProvider).build();RequestConfig config = RequestConfig.custom().setProxy(proxy).build();// 设置参数List<NameValuePair> formparams = new ArrayList<NameValuePair>();formparams.add(new BasicNameValuePair("timestamp", timestamp));formparams.add(new BasicNameValuePair("sign", sign));UrlEncodedFormEntity uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8");httpPost.setEntity(uefEntity);httpPost.setConfig(config);// 得到响应状态码res = httpclient.execute(httpPost,context);//  获取返回对象HttpEntity entity = res.getEntity();// 通过EntityUtils获取返回结果内容result = EntityUtils.toString(entity);} catch (Exception e) {e.printStackTrace();} finally {//  最后一定要释放资源if(httpclient!=null) {try {httpclient.close();} catch (Exception e) {e.printStackTrace();}}}return result;}