七大主流的HttpClient程序比较
Java中主流的HttpClient程序包括Apache HttpClient、OkHttp和Java自带的HttpURLConnection。Apache HttpClient是一个开源的Java HTTP客户端库，提供了一种高效、灵活、可扩展的方式来发送HTTP请求和处理HTTP响应。OkHttp具有简单的API、高效的连接管理和请求缓存机制，以及对SPDY和HTTP/2的支持。HttpURLConnection是Java自带的HTTP客户端，提供了基本的HTTP请求和响应功能。这些HttpClient程序都可以用于在Java应用程序中发送HTTP请求并处理HTTP响应。
在你刚刚选择从HttpURLConnection转成Apache Httpclient时，发现好像新出了个okHttp了。你还在犹豫要不要换成okHttp时，Android已经废除了Apache Httpclient改用okHttp了。那这时你开始纠结继续用Apache Httpclient还是改用okHttp时，okHttp的公司Square又出了Retrofit，网友已经在说既然你都用了okHttp为何不直接使用Retrofit？
1 HttpURLConnection
HttpURLConnection是java的标准类，什么都没封装，用起来太原始，不方便，比如重访问的自定义，以及一些高级功能等。
2 java.net.http.HttpClient
jdk11正式启用自带HttpClient，代替之前比较旧的HttpURLConnection。其实从java9的jdk.incubator.httpclient模块迁移到java.net.http模块，包名由jdk.incubator.http改为java.net.http。
3 Apache HttpClient
在Android中，AndroidSDK中集成了Apache的HttpClient模块，HttpClient就是一个增强版的HttpURLConnection，它只是关注于如何发送请求、接收响应，以及管理HTTP连接。如果做好封装或者使用android-async-http，Afinal，Xutils也能挺简单的完成http请求，但是Android6.0谷歌因为和Apache更新难以同步等原因吧已经放弃了HttpClient，改于了okHttp。
//httpclient官网示例 ClientMultiThreadedExecution.java
PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
cm.setMaxTotal(100);
CloseableHttpClient httpclient = HttpClients.custom()
.setConnectionManager(cm)
.build();
.........
} finally {
httpclient.close();
}
//超时配置到Request级
RequestConfig requestConfig = RequestConfig.copy(defaultRequestConfig)
.setSocketTimeout(5000)
.setConnectTimeout(5000)
.setConnectionRequestTimeout(5000)
.setProxy(new HttpHost("myotherproxy", 8080))
.build();
4 okHttp
OkHttp 是 Square 公司开源的针对 Java 和 Android 程序，封装的一个高性能 http 请求库。OKHttp 类似于 HttpUrlConnection， 是基于传输层实现应用层协议的网络框架。 而不止是一个 Http 请求应用的库。
okHttp的优势：
链接复用
Response 缓存和 Cookie
默认 GZIP
请求失败自动重连
DNS 扩展
Http2/SPDY/WebSocket 协议支持
默认情况下，OKHttp会自动处理常见的网络问题：像二次连接、SSL的握手问题。
从4开始HttpURLConnection的底层实现采用的是okHttp.
5 Retrofit
Retrofit 是 Square 公司出品的默认基于 OkHttp 封装的一套 RESTful 网络请求框架，RESTful 可以说是目前流行的一套 api 设计的风格，并不是标准。Retrofit 的封装可以说是很强大，里面涉及到一堆的设计模式，你可以通过注解直接配置请求，你可以使用不同的 http 客户端，虽然默认是用 OKhttp ，可以使用不同 Json Converter 来序列化数据，同时提供对 RxJava 的支持，使用 Retrofit + OkHttp + RxJava + Dagger2 可以说是目前比较潮的一套框架，但是需要有比较高的门槛。
Retrofit retrofit =
new Retrofit.Builder()
.baseUrl(API_URL)
.addConverterFactory(GsonConverterFactory.create())
.build();
5.1 如何信任自签或过期的SSL证书？
以下以https://futurestud.io/tutorials/retrofit-2-how-to-trust-unsafe-ssl-certificates-self-signed-expired网站提供的一个用例做简要说明。
package okhttp3.recipes;
import java.io.IOException;
import java.security.cert.X509Certificate;
import okhttp3.Headers;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import okhttp3.tls.Certificates;
import okhttp3.tls.HandshakeCertificates;
public final class CustomTrust {
// PEM files for root certificates of Comodo and Entrust. These two CAs are sufficient to view
// https://publicobject.com (Comodo) and https://squareup.com (Entrust). But they aren't
// sufficient to connect to most HTTPS sites including https://godaddy.com and https://visa.com.
// Typically developers will need to get a PEM file from their organization's TLS administrator.
final X509Certificate comodoRsaCertificationAuthority = Certificates.decodeCertificatePem(""
+ "-----BEGIN CERTIFICATE-----\n"
+ "MIIF2DCCA8CgAwIBAgIQTKr5yttjb+Af907YWwOGnTANBgkqhkiG9w0BAQwFADCB\n"
+ "hTELMAkGA1UEBhMCR0IxGzAZBgNVBAgTEkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4G\n"
+ "A1UEBxMHU2FsZm9yZDEaMBgGA1UEChMRQ09NT0RPIENBIExpbWl0ZWQxKzApBgNV\n"
+ "BAMTIkNPTU9ETyBSU0EgQ2VydGlmaWNhdGlvbiBBdXRob3JpdHkwHhcNMTAwMTE5\n"
+ "MDAwMDAwWhcNMzgwMTE4MjM1OTU5WjCBhTELMAkGA1UEBhMCR0IxGzAZBgNVBAgT\n"
+ "EkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4GA1UEBxMHU2FsZm9yZDEaMBgGA1UEChMR\n"
+ "Q09NT0RPIENBIExpbWl0ZWQxKzApBgNVBAMTIkNPTU9ETyBSU0EgQ2VydGlmaWNh\n"
+ "dGlvbiBBdXRob3JpdHkwggIiMA0GCSqGSIb3DQEBAQUAA4ICDwAwggIKAoICAQCR\n"
+ "6FSS0gpWsawNJN3Fz0RndJkrN6N9I3AAcbxT38T6KhKPS38QVr2fcHK3YX/JSw8X\n"
+ "pz3jsARh7v8Rl8f0hj4K+j5c+ZPmNHrZFGvnnLOFoIJ6dq9xkNfs/Q36nGz637CC\n"
+ "9BR++b7Epi9Pf5l/tfxnQ3K9DADWietrLNPtj5gcFKt+5eNu/Nio5JIk2kNrYrhV\n"
+ "/erBvGy2i/MOjZrkm2xpmfh4SDBF1a3hDTxFYPwyllEnvGfDyi62a+pGx8cgoLEf\n"
+ "Zd5ICLqkTqnyg0Y3hOvozIFIQ2dOciqbXL1MGyiKXCJ7tKuY2e7gUYPDCUZObT6Z\n"
+ "+pUX2nwzV0E8jVHtC7ZcryxjGt9XyD+86V3Em69FmeKjWiS0uqlWPc9vqv9JWL7w\n"
+ "qP/0uK3pN/u6uPQLOvnoQ0IeidiEyxPx2bvhiWC4jChWrBQdnArncevPDt09qZah\n"
+ "SL0896+1DSJMwBGB7FY79tOi4lu3sgQiUpWAk2nojkxl8ZEDLXB0AuqLZxUpaVIC\n"
+ "u9ffUGpVRr+goyhhf3DQw6KqLCGqR84onAZFdr+CGCe01a60y1Dma/RMhnEw6abf\n"
+ "Fobg2P9A3fvQQoh/ozM6LlweQRGBY84YcWsr7KaKtzFcOmpH4MN5WdYgGq/yapiq\n"
+ "crxXStJLnbsQ/LBMQeXtHT1eKJ2czL+zUdqnR+WEUwIDAQABo0IwQDAdBgNVHQ4E\n"
+ "FgQUu69+Aj36pvE8hI6t7jiY7NkyMtQwDgYDVR0PAQH/BAQDAgEGMA8GA1UdEwEB\n"
+ "/wQFMAMBAf8wDQYJKoZIhvcNAQEMBQADggIBAArx1UaEt65Ru2yyTUEUAJNMnMvl\n"
+ "wFTPoCWOAvn9sKIN9SCYPBMtrFaisNZ+EZLpLrqeLppysb0ZRGxhNaKatBYSaVqM\n"
+ "4dc+pBroLwP0rmEdEBsqpIt6xf4FpuHA1sj+nq6PK7o9mfjYcwlYRm6mnPTXJ9OV\n"
+ "2jeDchzTc+CiR5kDOF3VSXkAKRzH7JsgHAckaVd4sjn8OoSgtZx8jb8uk2Intzna\n"
+ "FxiuvTwJaP+EmzzV1gsD41eeFPfR60/IvYcjt7ZJQ3mFXLrrkguhxuhoqEwWsRqZ\n"
+ "CuhTLJK7oQkYdQxlqHvLI7cawiiFwxv/0Cti76R7CZGYZ4wUAc1oBmpjIXUDgIiK\n"
+ "boHGhfKppC3n9KUkEEeDys30jXlYsQab5xoq2Z0B15R97QNKyvDb6KkBPvVWmcke\n"
+ "jkk9u+UJueBPSZI9FoJAzMxZxuY67RIuaTxslbH9qh17f4a+Hg4yRvv7E491f0yL\n"
+ "S0Zj/gA0QHDBw7mh3aZw4gSzQbzpgJHqZJx64SIDqZxubw5lT2yHh17zbqD5daWb\n"
+ "QOhTsiedSrnAdyGN/4fy3ryM7xfft0kL0fJuMAsaDk527RH89elWsn2/x20Kk4yl\n"
+ "0MC2Hb46TpSi125sC8KKfPog88Tk5c0NqMuRkrF8hey1FGlmDoLnzc7ILaZRfyHB\n"
+ "NVOFBkpdn627G190\n"
+ "-----END CERTIFICATE-----\n");
final X509Certificate entrustRootCertificateAuthority = Certificates.decodeCertificatePem(""
+ "-----BEGIN CERTIFICATE-----\n"
+ "MIIEkTCCA3mgAwIBAgIERWtQVDANBgkqhkiG9w0BAQUFADCBsDELMAkGA1UEBhMC\n"
+ "VVMxFjAUBgNVBAoTDUVudHJ1c3QsIEluYy4xOTA3BgNVBAsTMHd3dy5lbnRydXN0\n"
+ "Lm5ldC9DUFMgaXMgaW5jb3Jwb3JhdGVkIGJ5IHJlZmVyZW5jZTEfMB0GA1UECxMW\n"
+ "KGMpIDIwMDYgRW50cnVzdCwgSW5jLjEtMCsGA1UEAxMkRW50cnVzdCBSb290IENl\n"
+ "cnRpZmljYXRpb24gQXV0aG9yaXR5MB4XDTA2MTEyNzIwMjM0MloXDTI2MTEyNzIw\n"
+ "NTM0MlowgbAxCzAJBgNVBAYTAlVTMRYwFAYDVQQKEw1FbnRydXN0LCBJbmMuMTkw\n"
+ "NwYDVQQLEzB3d3cuZW50cnVzdC5uZXQvQ1BTIGlzIGluY29ycG9yYXRlZCBieSBy\n"
+ "ZWZlcmVuY2UxHzAdBgNVBAsTFihjKSAyMDA2IEVudHJ1c3QsIEluYy4xLTArBgNV\n"
+ "BAMTJEVudHJ1c3QgUm9vdCBDZXJ0aWZpY2F0aW9uIEF1dGhvcml0eTCCASIwDQYJ\n"
+ "KoZIhvcNAQEBBQADggEPADCCAQoCggEBALaVtkNC+sZtKm9I35RMOVcF7sN5EUFo\n"
+ "Nu3s/poBj6E4KPz3EEZmLk0eGrEaTsbRwJWIsMn/MYszA9u3g3s+IIRe7bJWKKf4\n"
+ "4LlAcTfFy0cOlypowCKVYhXbR9n10Cv/gkvJrT7eTNuQgFA/CYqEAOwwCj0Yzfv9\n"
+ "KlmaI5UXLEWeH25DeW0MXJj+SKfFI0dcXv1u5x609mhF0YaDW6KKjbHjKYD+JXGI\n"
+ "rb68j6xSlkuqUY3kEzEZ6E5Nn9uss2rVvDlUccp6en+Q3X0dgNmBu1kmwhH+5pPi\n"
+ "94DkZfs0Nw4pgHBNrziGLp5/V6+eF67rHMsoIV+2HNjnogQi+dPa2MsCAwEAAaOB\n"
+ "sDCBrTAOBgNVHQ8BAf8EBAMCAQYwDwYDVR0TAQH/BAUwAwEB/zArBgNVHRAEJDAi\n"
+ "gA8yMDA2MTEyNzIwMjM0MlqBDzIwMjYxMTI3MjA1MzQyWjAfBgNVHSMEGDAWgBRo\n"
+ "kORnpKZTgMeGZqTx90tD+4S9bTAdBgNVHQ4EFgQUaJDkZ6SmU4DHhmak8fdLQ/uE\n"
+ "vW0wHQYJKoZIhvZ9B0EABBAwDhsIVjcuMTo0LjADAgSQMA0GCSqGSIb3DQEBBQUA\n"
+ "A4IBAQCT1DCw1wMgKtD5Y+iRDAUgqV8ZyntyTtSx29CW+1RaGSwMCPeyvIWonX9t\n"
+ "O1KzKtvn1ISMY/YPyyYBkVBs9F8U4pN0wBOeMDpQ47RgxRzwIkSNcUesyBrJ6Zua\n"
+ "AGAT/3B+XxFNSRuzFVJ7yVTav52Vr2ua2J7p8eRDjeIRRDq/r72DQnNSi6q7pynP\n"
+ "9WQcCk3RvKqsnyrQ/39/2n3qse0wJcGE2jTSW3iDVuycNsMm4hH2Z0kdkquM++v/\n"
+ "eu6FSqdQgPCnXEqULl8FmTxSQeDNtGPPAUO6nIPcj2A781q0tHuu2guQOHXvgR1m\n"
+ "0vdXcDazv/wor3ElhVsT/h5/WrQ8\n"
+ "-----END CERTIFICATE-----\n");
final X509Certificate letsEncryptCertificateAuthority = Certificates.decodeCertificatePem(""
+ "-----BEGIN CERTIFICATE-----\n"
+ "MIIEkjCCA3qgAwIBAgIQCgFBQgAAAVOFc2oLheynCDANBgkqhkiG9w0BAQsFADA/\n"
+ "MSQwIgYDVQQKExtEaWdpdGFsIFNpZ25hdHVyZSBUcnVzdCBDby4xFzAVBgNVBAMT\n"
+ "DkRTVCBSb290IENBIFgzMB4XDTE2MDMxNzE2NDA0NloXDTIxMDMxNzE2NDA0Nlow\n"
+ "SjELMAkGA1UEBhMCVVMxFjAUBgNVBAoTDUxldCdzIEVuY3J5cHQxIzAhBgNVBAMT\n"
+ "GkxldCdzIEVuY3J5cHQgQXV0aG9yaXR5IFgzMIIBIjANBgkqhkiG9w0BAQEFAAOC\n"
+ "AQ8AMIIBCgKCAQEAnNMM8FrlLke3cl03g7NoYzDq1zUmGSXhvb418XCSL7e4S0EF\n"
+ "q6meNQhY7LEqxGiHC6PjdeTm86dicbp5gWAf15Gan/PQeGdxyGkOlZHP/uaZ6WA8\n"
+ "SMx+yk13EiSdRxta67nsHjcAHJyse6cF6s5K671B5TaYucv9bTyWaN8jKkKQDIZ0\n"
+ "Z8h/pZq4UmEUEz9l6YKHy9v6Dlb2honzhT+Xhq+w3Brvaw2VFn3EK6BlspkENnWA\n"
+ "a6xK8xuQSXgvopZPKiAlKQTGdMDQMc2PMTiVFrqoM7hD8bEfwzB/onkxEz0tNvjj\n"
+ "/PIzark5McWvxI0NHWQWM6r6hCm21AvA2H3DkwIDAQABo4IBfTCCAXkwEgYDVR0T\n"
+ "AQH/BAgwBgEB/wIBADAOBgNVHQ8BAf8EBAMCAYYwfwYIKwYBBQUHAQEEczBxMDIG\n"
+ "CCsGAQUFBzABhiZodHRwOi8vaXNyZy50cnVzdGlkLm9jc3AuaWRlbnRydXN0LmNv\n"
+ "bTA7BggrBgEFBQcwAoYvaHR0cDovL2FwcHMuaWRlbnRydXN0LmNvbS9yb290cy9k\n"
+ "c3Ryb290Y2F4My5wN2MwHwYDVR0jBBgwFoAUxKexpHsscfrb4UuQdf/EFWCFiRAw\n"
+ "VAYDVR0gBE0wSzAIBgZngQwBAgEwPwYLKwYBBAGC3xMBAQEwMDAuBggrBgEFBQcC\n"
+ "ARYiaHR0cDovL2Nwcy5yb290LXgxLmxldHNlbmNyeXB0Lm9yZzA8BgNVHR8ENTAz\n"
+ "MDGgL6AthitodHRwOi8vY3JsLmlkZW50cnVzdC5jb20vRFNUUk9PVENBWDNDUkwu\n"
+ "Y3JsMB0GA1UdDgQWBBSoSmpjBH3duubRObemRWXv86jsoTANBgkqhkiG9w0BAQsF\n"
+ "AAOCAQEA3TPXEfNjWDjdGBX7CVW+dla5cEilaUcne8IkCJLxWh9KEik3JHRRHGJo\n"
+ "uM2VcGfl96S8TihRzZvoroed6ti6WqEBmtzw3Wodatg+VyOeph4EYpr/1wXKtx8/\n"
+ "wApIvJSwtmVi4MFU5aMqrSDE6ea73Mj2tcMyo5jMd6jmeWUHK8so/joWUoHOUgwu\n"
+ "X4Po1QYz+3dszkDqMp4fklxBwXRsW10KXzPMTZ+sOPAveyxindmjkW8lGy+QsRlG\n"
+ "PfZ+G6Z6h7mjem0Y+iWlkYcV4PIWL1iwBi8saCbGS5jN2p8M+X+Q7UNKEkROb3N6\n"
+ "KOqkqm57TH2H3eDJAkSnh6/DNFu0Qg==\n"
+ "-----END CERTIFICATE-----");
private final OkHttpClient client;
public CustomTrust() {
// This implementation just embeds the PEM files in Java strings; most applications will
// instead read this from a resource file that gets bundled with the application.
HandshakeCertificates certificates = new HandshakeCertificates.Builder()
.addTrustedCertificate(letsEncryptCertificateAuthority)
.addTrustedCertificate(entrustRootCertificateAuthority)
.addTrustedCertificate(comodoRsaCertificationAuthority)
// Uncomment if standard certificates are also required.
//.addPlatformTrustedCertificates()
.build();
client = new OkHttpClient.Builder()
.sslSocketFactory(certificates.sslSocketFactory(), certificates.trustManager())
.build();
}
public void run() throws Exception {
Request request = new Request.Builder()
.url("https://publicobject.com/helloworld.txt")
.build();
try (Response response = client.newCall(request).execute()) {
if (!response.isSuccessful()) {
Headers responseHeaders = response.headers();
for (int i = 0; i < responseHeaders.size(); i++) {
System.out.println(responseHeaders.name(i) + ": " + responseHeaders.value(i));
}
throw new IOException("Unexpected code " + response);
}
System.out.println(response.body().string());
}
}
public static void main(String... args) throws Exception {
new CustomTrust().run();
}
}
5.2 安卓程序中如何实现授权？
https://medium.com/@thoolab/how-to-implement-retrofit-basic-authentication-in-android-kotlin-9f25abe34dda
6 RestTemplate
RestTemplate是 Spring 提供的用于访问Rest服务的客户端， RestTemplate 提供了多种便捷访问远程Http服务的方法,能够大大提高客户端的编写效率。
7 OpenFeign
可插拔的注解支持，包括Feign注解和JAX-RS注解。
支持可插拔的HTTP编码器和解码器（Gson，Jackson，Sax，JAXB，JAX-RS，SOAP）。
支持Hystrix和它的Fallback。
支持Ribbon的负载均衡。
支持HTTP请求和响应的压缩。
灵活的配置：基于 name 粒度进行配置
支持多种客户端：JDK URLConnection、apache httpclient、okhttp，ribbon）
支持日志
支持错误重试
url支持占位符
可以不依赖注册中心独立运行
8 总结
在你还在纠结选择apache httpclient时，Android已经不用它了，改用okhttp了
当你还在纠结选择apache httpclient还是okhttp时，Square已经出了Retrofit，网友已经在说既然你都用了okhttp为何不直接使用Retrofit
总的来说技术变化更新都比较快，得跟上技术的发展。一般来说没有使用springcloud话可以选择Retrofit，如果使用了springcloud可以使用OpenFeign+okHttp。