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

public class HttpTests {

    CloseableHttpClient httpClient;

    // 序列化与反序列化
    private static final ObjectMapper MAPPER = new ObjectMapper();

    @Before
    public void init() {
        httpClient = HttpClients.createDefault();
    }

    @Test
    public void testGet() throws IOException {
        HttpGet request = new HttpGet("http://www.baidu.com/s?ie=UTF-8&wd=java");
        String response = this.httpClient.execute(request, new BasicResponseHandler());
        User user = MAPPER.readValue(response, User.class);
        String usertToString = MAPPER.writeValueAsString(user);
    }
}

原生OkHttp

private OkHttpClient client = new OkHttpClient();

@Test
public void testGet() throws IOException {
    String api = "/api/files/1";
    String url = String.format("%s%s", BASE_URL, api);
    Request request = new Request.Builder()
            .url(url)
            .get() 
            .build();
    final Call call = client.newCall(request);
    Response response = call.execute();
    System.out.println(response.body().string());
}

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）。

@SpringBootApplication
public class HttpDemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(HttpDemoApplication.class, args);
    }

    @Bean
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

@RunWith(SpringRunner.class)
@SpringBootTest(classes = HttpDemoApplication.class)
public class HttpDemoApplicationTests {

    @Autowired
    private RestTemplate restTemplate;

    @Test
    public void httpGet() {
        User user = this.restTemplate.getForObject("http://localhost:8888/user/42", User.class);
        System.out.println(user);
    }

}