HTTPS通过proxy访问服务器接口

RestTemplate restTemplate = new RestTemplate();

     CredentialsProvider credsProvider = new BasicCredentialsProvider();
     credsProvider.setCredentials( new AuthScope("172.21.21.18", 8080),new UsernamePasswordCredentials("huangrong", "Firewall123") );
     HttpClientBuilder clientBuilder = HttpClientBuilder.create();

     clientBuilder.useSystemProperties();
     clientBuilder.setProxy(new HttpHost("172.21.21.18", 8080));
     clientBuilder.setDefaultCredentialsProvider(credsProvider);
     clientBuilder.setProxyAuthenticationStrategy(new ProxyAuthenticationStrategy());
     CloseableHttpClient client = clientBuilder.build();
     HttpComponentsClientHttpRequestFactory factory = new HttpComponentsClientHttpRequestFactory();
     factory.setHttpClient(client);
     restTemplate.setRequestFactory(factory);
     String re = restTemplate.getForObject("http://172.22.1.55:8080/asdfa/test", String.class);
     System.out.println(re);

这段代码可以访问http的接口 通过172.21.21.18:8080代理服务器。但是如果想访问https的接口应该怎么处理？ 试 了很久一直没有通。有没有高手来补充一下完成的代码

http://www.open-open.com/lib/view/open1326367644687.html