RPC还是HTTP？HttpClient还是OKHttp？

RPC

远程过程调用
自定义数据格式
速度快
效率高

典型代表：webservice、dubbo

HTTP

网络传输协议
规定数据传输格式
服务调用和提供方没有技术限定
消息封装臃肿

典型代表：RestFul。

HTTP客户端工具：HttpClient、OKHttp、URLConnection。他们之间的优缺点对比：

HttpClient

网络框架
网络请求封装完善
api多，难扩展
稳定

OKHttp

支持jdk1.7以上
网络连接效率高。同一IP和端口请求重用一个socket
网络请求成熟
网络切换在线程，不能直接刷新UI

URLConnection

轻量级HTTP客户端
api少，易扩展

原生HttpClient

 1 public class HttpTests {
 2 
 3     CloseableHttpClient httpClient;
 4 
 5     // 序列化与反序列化
 6     private static final ObjectMapper MAPPER = new ObjectMapper();
 7 
 8     @Before
 9     public void init() {
10         httpClient = HttpClients.createDefault();
11     }
12 
13     @Test
14     public void testGet() throws IOException {
15         HttpGet request = new HttpGet("http://www.baidu.com/s?ie=UTF-8&wd=java");
16         String response = this.httpClient.execute(request, new BasicResponseHandler());
17         User user = MAPPER.readValue(response, User.class);
18         String usertToString = MAPPER.writeValueAsString(user);
19     }
20 }

原生OkHttp

 1 private OkHttpClient client = new OkHttpClient();
 2 
 3 @Test
 4 public void testGet() throws IOException {
 5     String api = "/api/files/1";
 6     String url = String.format("%s%s", BASE_URL, api);
 7     Request request = new Request.Builder()
 8             .url(url)
 9             .get() 
10             .build();
11     final Call call = client.newCall(request);
12     Response response = call.execute();
13     System.out.println(response.body().string());
14 }

详细可以参考https://www.cnblogs.com/zk-blog/p/12465951.html

RestTemplate

Spring的RestTemplate，对基于HTTP的客户端进行封装，实现对象与json的序列化与反序列化。支持HttpClient、OkHttp、URLConnection（默认的）。

 1 @SpringBootApplication
 2 public class HttpDemoApplication {
 3 
 4     public static void main(String[] args) {
 5         SpringApplication.run(HttpDemoApplication.class, args);
 6     }
 7 
 8     @Bean
 9     public RestTemplate restTemplate() {
10         return new RestTemplate();
11     }
12 }

 1 @RunWith(SpringRunner.class)
 2 @SpringBootTest(classes = HttpDemoApplication.class)
 3 public class HttpDemoApplicationTests {
 4 
 5     @Autowired
 6     private RestTemplate restTemplate;
 7 
 8     @Test
 9     public void httpGet() {
10         User user = this.restTemplate.getForObject("http://localhost:8888/user/42", User.class);
11         System.out.println(user);
12     }
13 
14 }