SpringBoot集成HttpClient_springboot requestconfig-优快云博客

##HttpClient几个主要概念

CloseableHttpClient
用于发送请求，因为是线程安全的，所以只需要在程序中创建一个单例。
RequestConfig
用于配置每个请求的各项timeout等等
PoolingHttpClientConnectionManager
用于配置连接池
ConnetionKeepAliveStrategy
用于创建KeepAlive策略。
HTTP 1.1长连接
HTTP 1.1默认支持长连接，在header中会带有keep-alive。
使用HttpClient的线程池，可以利用开启的长连接来减少创建连接的开销。

在整个集成HttpClient的过程中，主要顺序是：
配置KeepAlive策略 -> 配置连接池 -> 配置RequestConfig -> 配置HttpClient

另外也可以通HttpClient来配置自己的RestTemplate

##HttpClient集成
依赖：org.apache.httpcomponents:httpclient:4.5.7

集成配置（Kotlin）

@Configuration
class HttpConfig {

    @Primary
    @Bean
    fun httpClient(requestConfig: RequestConfig, httpClientConnectionManager: HttpClientConnectionManager): CloseableHttpClient {
        return HttpClientBuilder
                .create()
                //.addInterceptorFirst(LogbookHttpRequestInterceptor(OutgoingLogbook.logbook()))
                //.addInterceptorFirst(LogbookHttpResponseInterceptor())
                .setConnectionManager(httpClientConnectionManager)
                .setDefaultRequestConfig(requestConfig)
                .setKeepAliveStrategy(KeepAliveStrategy())
                .build()
    }

    @Primary
    @Bean
    fun sslRestTemplate(httpClient: CloseableHttpClient, objectMapper: ObjectMapper): RestTemplate {
        return restTemplateFor(httpClient, objectMapper)
    }

    private fun restTemplateFor(httpClient: CloseableHttpClient,
                                objectMapper: ObjectMapper): RestTemplate {
        return RestTemplateBuilder()
                .requestFactory { BufferingClientHttpRequestFactory(HttpComponentsClientHttpRequestFactory(httpClient)) }
                .messageConverters(
                        MappingJackson2HttpMessageConverter(objectMapper),
                        ByteArrayHttpMessageConverter(),
                        StringHttpMessageConverter(),
                        ResourceHttpMessageConverter()
                )
                .build()
    }

    @Bean
    fun httpClientConnectionManager(sslContext: SSLContext): HttpClientConnectionManager {
        // 此处是关于SSL的配置，如果需要请求https且需要用连接池，需要将该factory配置于此处
        val sslConnectionSocketFactory = SSLConnectionSocketFactory(sslContext, NoopHostnameVerifier.INSTANCE)
        val socketFactoryRegistry = RegistryBuilder.create<ConnectionSocketFactory>()
                .register("http", PlainConnectionSocketFactory.INSTANCE)
                .register("https", sslConnectionSocketFactory)
                .build()

        val connectionManager = PoolingHttpClientConnectionManager(socketFactoryRegistry)
        connectionManager.maxTotal = 100
        connectionManager.defaultMaxPerRoute = 2
        return connectionManager
    }

    @Bean
    fun requestConfig(): RequestConfig {
        return RequestConfig.custom().setConnectTimeout(3000).setSocketTimeout(1000).setConnectionRequestTimeout(500).build()
    }

    private class KeepAliveStrategy : ConnectionKeepAliveStrategy {
        override fun getKeepAliveDuration(response: HttpResponse, context: HttpContext): Long {

            val it = BasicHeaderElementIterator(response.headerIterator(HTTP.CONN_KEEP_ALIVE))
            while (it.hasNext()) {
                val headerElement = it.nextElement()
                val param = headerElement.name
                val value = headerElement.value
                if (value != null && "timeout".equals(param, ignoreCase = true)) {
                    return value.toLong()
                }
            }

            return 60 * 1000
        }
    }
}

##HttpClient使用