客户端 RestTemplate的使用，自定义KeepAlive策略策略

本文链接：https://blog.youkuaiyun.com/haponchang/article/details/94435419

本文详细介绍了如何在客户端使用RestTemplate进行HTTP请求，并重点讨论了如何实现自定义的KeepAlive连接策略，以优化网络连接的复用和管理，提升性能。

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RestTemplate的使用代码（客户端）：
（spring 启动类 和 keepalive策略）

/**
 * SpringBoot启动类
 */
@SpringBootApplication
@Slf4j
public class CustomerServiceApplication implements ApplicationRunner {
   @Autowired
   private RestTemplate restTemplate;

   public static void main(String[] args) {
      new SpringApplicationBuilder()
            .sources(CustomerServiceApplication.class)
            .bannerMode(Banner.Mode.OFF)
            .web(WebApplicationType.NONE)
            .run(args);
   }

   @Bean
   public HttpComponentsClientHttpRequestFactory requestFactory() {
      PoolingHttpClientConnectionManager connectionManager =
            new PoolingHttpClientConnectionManager(30, TimeUnit.SECONDS);
      connectionManager.setMaxTotal(200);
      connectionManager.setDefaultMaxPerRoute(20);

      CloseableHttpClient httpClient = HttpClients.custom()
            .setConnectionManager(connectionManager)
            .evictIdleConnections(30, TimeUnit.SECONDS)
            .disableAutomaticRetries()
            // 有 Keep-Alive 认里面的值，没有的话永久有效
            //.setKeepAliveStrategy(DefaultConnectionKeepAliveStrategy.INSTANCE)
            // 换成自定义的
            .setKeepAliveStrategy(new CustomConnectionKeepAliveStrategy())
            .build();

      HttpComponentsClientHttpRequestFactory requestFactory =
            new HttpComponentsClientHttpRequestFactory(httpClient);

      return requestFactory;
   }

   @Bean
   public RestTemplate restTemplate(RestTemplateBuilder builder) {
//    return new RestTemplate();

      return builder
            .setConnectTimeout(Duration.ofMillis(100))
            .setReadTimeout(Duration.ofMillis(500))
            .requestFactory(this::requestFactory)
            .build();
   }

   @Override
   public void run(ApplicationArguments args) throws Exception {
      URI uri = UriComponentsBuilder
            .fromUriString("http://localhost:8080/coffee/?name={name}")
            .build("mocha");
      RequestEntity<Void> req = RequestEntity.get(uri)
//          .accept(MediaType.APPLICATION_XML)
            .build();
      ResponseEntity<String> resp = restTemplate.exchange(req, String.class);
      log.info("Response Status: {}, Response Headers: {}", resp.getStatusCode(), resp.getHeaders().toString());
      log.info("Coffee: {}", resp.getBody());
   }
}


/**
 * KeepAlive策略
 */
public class CustomConnectionKeepAliveStrategy implements ConnectionKeepAliveStrategy {
    private final long DEFAULT_SECONDS = 30;

    @Override
    public long getKeepAliveDuration(HttpResponse response, HttpContext context) {
        return Arrays.asList(response.getHeaders(HTTP.CONN_KEEP_ALIVE))
                .stream()
                .filter(h -> StringUtils.equalsIgnoreCase(h.getName(), "timeout")
                        && StringUtils.isNumeric(h.getValue()))
                .findFirst()
                .map(h -> NumberUtils.toLong(h.getValue(), DEFAULT_SECONDS))
                .orElse(DEFAULT_SECONDS) * 1000;
    }
}

运行结果：