采用Apache的httpclient作为RestTemplate的连接池配置，同时增加重试功能。

依赖

<dependency>
    <groupId>org.springframework.retry</groupId>
    <artifactId>spring-retry</artifactId>
</dependency>
<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
</dependency>
<dependency>
    <groupId>commons-collections</groupId>
    <artifactId>commons-collections</artifactId>
</dependency>

httpclient配置

@Data
@ConfigurationProperties(prefix = "http-client.conn-pool")
public class HttpClientConfig {
    private Integer maxTotal = 600;
    private Integer defaultMaxPerRoute = 300;
    private List<HttpHostConfiguration> maxPerRoutes;

    private Integer connectionRequestTimeout = 1000;
    private Integer connectTimeout = 10000;
    private Integer socketTimeout = 30000;

    @Data
    static class HttpHostConfiguration {
        private String scheme;
        private String host;
        private Integer port;
        private Integer maxPerRoute;
    }
}

添加日志拦截器

@Slf4j
public class LoggingClientHttpRequestInterceptor implements ClientHttpRequestInterceptor {

    @Override
    public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {
        traceRequest(request, body);
        long start = System.currentTimeMillis();
        ClientHttpResponse response = execution.execute(request, body);
        log.info("LoggingClientHttpRequestInterceptor traceRequest {} total spend {} ms", request.getURI(), System.currentTimeMillis() - start);
        traceResponse(response);
        return response;
    }

    private void traceRequest(HttpRequest request, byte[] body) throws IOException {
        log.info("LoggingClientHttpRequestInterceptor traceRequest. URI:{},Method:{},Request body:{},Headers:{}",
                request.getURI(), request.getMethod(), new String(body, StandardCharsets.UTF_8), request.getHeaders());
    }

    private void traceResponse(ClientHttpResponse response) throws IOException {
        StringBuilder inputStringBuilder = new StringBuilder();
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(response.getBody(), StandardCharsets.UTF_8));
        String line = bufferedReader.readLine();
        while (line != null) {
            inputStringBuilder.append(line);
            inputStringBuilder.append('\n');
            line = bufferedReader.readLine();
        }
        log.info("LoggingClientHttpRequestInterceptor traceResponse. Status code:{},Status text:{},Response body:{},Headers:{}",
                response.getStatusCode(), response.getStatusText(), inputStringBuilder.toString(), response.getHeaders());
    }

}

连接池配置

@Slf4j
@Configuration
@ConditionalOnClass(value = {RestTemplate.class, CloseableHttpClient.class})
@EnableConfigurationProperties(HttpClientConfig.class)
public class RestTemplateConfig {

    @Bean
    public RestTemplate restTemplate(ClientHttpRequestFactory httpRequestFactory) {
        RestTemplate restTemplate = new RestTemplate(new BufferingClientHttpRequestFactory(httpRequestFactory));
        restTemplate.getInterceptors().add(new LoggingClientHttpRequestInterceptor());
        log.info("初始化restTemplate完成");
        return restTemplate;
    }

    @Bean
    public ClientHttpRequestFactory httpRequestFactory(HttpClient httpClient) {
        return new HttpComponentsClientHttpRequestFactory(httpClient);
    }

    @Bean
    public CloseableHttpClient httpClient(PoolingHttpClientConnectionManager poolingHttpClientConnectionManager, RequestConfig requestConfig) {
        return HttpClientBuilder.create()
                .setDefaultRequestConfig(requestConfig)
                .setConnectionManager(poolingHttpClientConnectionManager)
                .build();
    }

    @Bean
    public PoolingHttpClientConnectionManager poolingHttpClientConnectionManager(HttpClientConfig httpClientConfig) {
        PoolingHttpClientConnectionManager result = new PoolingHttpClientConnectionManager();
        result.setMaxTotal(httpClientConfig.getMaxTotal());
        result.setDefaultMaxPerRoute(httpClientConfig.getDefaultMaxPerRoute());
        if (CollectionUtils.isNotEmpty(httpClientConfig.getMaxPerRoutes())) {
            for (HttpClientConfig.HttpHostConfiguration httpHostConfig : httpClientConfig.getMaxPerRoutes()) {
                HttpHost host = new HttpHost(httpHostConfig.getHost(), httpHostConfig.getPort(), httpHostConfig.getScheme());
                result.setMaxPerRoute(new HttpRoute(host), httpHostConfig.getMaxPerRoute());
            }
        }
        return result;
    }

    @Bean
    public RequestConfig requestConfig(HttpClientConfig httpClientConfig) {
        return RequestConfig.custom()
                .setConnectionRequestTimeout(httpClientConfig.getConnectionRequestTimeout())
                .setConnectTimeout(httpClientConfig.getConnectTimeout())
                .setSocketTimeout(httpClientConfig.getSocketTimeout())
                .build();
    }
}

对post请求添加retry操作

@Service
@EnableRetry
public class RestTemplateService {
   @Resource
   private RestTemplate restTemplate;

   @Retryable(value = {RestClientException.class, ResourceAccessException.class}, maxAttempts = 2,
         backoff = @Backoff(delay = 500L))
   public <T> T postForObject(String url, Object request, Class<T> responseType){
      return restTemplate.postForObject(url, request, responseType);
   }

    public RestTemplate getRestTemplate(){
        return this.restTemplate;
    }
}