问题
项目中有个远程服务因为某些原因会访问不通，于是就在调用的那一步挂起无法结束了。
查看代码
代码大概如下
CloseableHttpClient closeableHttpClient = HttpClients.custom()
.setConnectionManager(manager)
.build();
HttpComponentsClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory();
requestFactory.setHttpClient(httpClient);
clientHttpRequestFactory.setConnectTimeout(1000);
RestTemplate restTemplate = new RestTemplate();
restTemplate.setRequestFactory(requestFactory);
分析
HttpComponentsClientHttpRequestFactory底层默认使用了apache的HttpClient，超时设置就针对其设置的。其实我们只需要设置ReadTimeout就好了。
CloseableHttpClient closeableHttpClient = HttpClients.custom() .setConnectionManager(manager) .build(); HttpComponentsClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory(); requestFactory.setHttpClient(httpClient); clientHttpRequestFactory.setConnectTimeout(1000); clientHttpRequestFactory.setReadTimeout(50); RestTemplate restTemplate = new RestTemplate(); restTemplate.setRequestFactory(requestFactory);
但我们发现，我们并没有使用默认的HttpClient，而是显式的指定了Client，我们在创建Client的时候也可以指定其的各种超时属性：
RequestConfig defaultRequestConfig = RequestConfig.custom() .setConnectTimeout(2 * 1000) .setSocketTimeout(5 * 1000) .setConnectionRequestTimeout(2 * 1000) .build(); CloseableHttpClient closeableHttpClient = HttpClients.custom() .setDefaultRequestConfig(getRequestConfig()) .setConnectionManager(manager) .build(); HttpComponentsClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory(); requestFactory.setHttpClient(httpClient); clientHttpRequestFactory.setConnectTimeout(1000); clientHttpRequestFactory.setReadTimeout(50); RestTemplate restTemplate = new RestTemplate(); restTemplate.setRequestFactory(requestFactory);
上面可以看到，我们在创建Client的时候指定了超时时间，也在创建HttpComponentsClientHttpRequestFactory的时候指定了超时时间，那么到底以哪个为准呢？
一探究竟
项目中使用的是spring web 4.3.5, 我们看看源代码的实现，以下是HttpComponentsClientHttpRequestFactory类的部分方法：
/** * Set the socket read timeout for the underlying HttpClient. * A timeout value of 0 specifies an infinite timeout. * <p>Additional properties can be configured by specifying a * {@link RequestConfig} instance on a custom {@link HttpClient}. * @param timeout the timeout value in milliseconds * @see RequestConfig#getSocketTimeout() */ public void setReadTimeout(int timeout) { Assert.isTrue(timeout >= 0, "Timeout must be a non-negative value"); this.requestConfig = requestConfigBuilder().setSocketTimeout(timeout).build(); setLegacySocketTimeout(getHttpClient(), timeout); }
@Override public ClientHttpRequest createRequest(URI uri, HttpMethod httpMethod) throws IOException { HttpUriRequest httpRequest = createHttpUriRequest(httpMethod, uri); postProcessHttpRequest(httpRequest); HttpContext context = createHttpContext(httpMethod, uri); if (context == null) { context = HttpClientContext.create(); } // Request configuration not set in the context if (context.getAttribute(HttpClientContext.REQUEST_CONFIG) == null) { // Use request configuration given by the user, when available RequestConfig config = null; if (httpRequest instanceof Configurable) { config = ((Configurable) httpRequest).getConfig(); } if (config == null) { config = createRequestConfig(getHttpClient()); } if (config != null) { context.setAttribute(HttpClientContext.REQUEST_CONFIG, config); } } if (this.bufferRequestBody) { return new HttpComponentsClientHttpRequest(getHttpClient(), httpRequest, context); } else { return new HttpComponentsStreamingClientHttpRequest(getHttpClient(), httpRequest, context); } }
/** * Create a default {@link RequestConfig} to use with the given client. * Can return {@code null} to indicate that no custom request config should * be set and the defaults of the {@link HttpClient} should be used. * <p>The default implementation tries to merge the defaults of the client * with the local customizations of this factory instance, if any. * @param client the {@link HttpClient} (or {@code HttpAsyncClient}) to check * @return the actual RequestConfig to use (may be {@code null}) * @since 4.2 * @see #mergeRequestConfig(RequestConfig) */ protected RequestConfig createRequestConfig(Object client) { if (client instanceof Configurable) { RequestConfig clientRequestConfig = ((Configurable) client).getConfig(); return mergeRequestConfig(clientRequestConfig); } return this.requestConfig; }
/** * Merge the given {@link HttpClient}-level {@link RequestConfig} with * the factory-level {@link RequestConfig}, if necessary. * @param clientConfig the config held by the current * @return the merged request config * @since 4.2 */ protected RequestConfig mergeRequestConfig(RequestConfig clientConfig) { if (this.requestConfig == null) { // nothing to merge return clientConfig; } RequestConfig.Builder builder = RequestConfig.copy(clientConfig); int connectTimeout = this.requestConfig.getConnectTimeout(); if (connectTimeout >= 0) { builder.setConnectTimeout(connectTimeout); } int connectionRequestTimeout = this.requestConfig.getConnectionRequestTimeout(); if (connectionRequestTimeout >= 0) { builder.setConnectionRequestTimeout(connectionRequestTimeout); } int socketTimeout = this.requestConfig.getSocketTimeout(); if (socketTimeout >= 0) { builder.setSocketTimeout(socketTimeout); } return builder.build(); }
我们可以看到，版本4.2之后，如果二者都进行了参数指定，会有一个mergeRequestConfig的操作，超时以HttpComponentsClientHttpRequestFactory类指定为为准。
结论
所以，针对本文一开始的问题，我们只需要设置HttpComponentsClientHttpRequestFactory实例的setReadTimeout方法即可。
参考
https://leokongwq.github.io/2018/11/21/springboot-resttempate-timout.html
https://www.cnblogs.com/softidea/p/6964347.html
但我们发现，我们显式的指定了Client，我们在创建Client的时候可以指定其的各种超时属性：