浏览器可以作为客户端向服务器发送Http请求，当需要访问后台或第三方Restful接口时，也可以用java实现客户端直接发get/post请求，获取数据。

https客户端

import javax.net.ssl.HttpsURLConnection;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.URL;
import java.security.KeyManagementException;
import java.security.NoSuchAlgorithmException;/*** 基于HttpsURLConnection实现客户端https请求**/
public class HttpsClientDemo {private static final String METHOD_GET = "GET";private static final String METHOD_POST = "POST";/*** doGet*/private static void httpsGet(String url) throws NoSuchAlgorithmException, KeyManagementException, IOException {// 创建连接对象HttpsURLConnection connection = getHttpsURLConnection(url, METHOD_GET);connection.connect();System.out.println("cipersuit used:" + connection.getCipherSuite());// 读取连接响应内容getresponse(connection);}/*** doPost*/private static void httpsPost(String url, String params) throws NoSuchAlgorithmException, IOException, KeyManagementException {// 创建连接对象HttpsURLConnection connection = getHttpsURLConnection(url, METHOD_POST);// 发送POST请求必须设置如下两行connection.setDoOutput(true);connection.setDoInput(true);connection.connect();// 获取URLConnection对象对应的输出流PrintWriter out = null;try {out = new PrintWriter(connection.getOutputStream());// 发送请求参数out.print(params);out.flush();} finally {if (out != null) {out.close();}}getresponse(connection);}/*** 读取连接响应内容*/private static void getresponse(HttpsURLConnection connection) throws IOException {BufferedReader br = null;try {br = new BufferedReader(new InputStreamReader(connection.getInputStream(), "UTF-8"));String inputLine;StringBuilder sb = new StringBuilder();while ((inputLine = br.readLine()) != null) {sb.append(inputLine);}System.out.println(sb.toString());System.out.println("responseMsg:" + connection.getResponseMessage() + "; responseCode:" + connection.getResponseCode());} finally {if (br != null) {br.close();}}}/*** 获取连接对象*/private static HttpsURLConnection getHttpsURLConnection(String url, String method) throws IOException, NoSuchAlgorithmException, KeyManagementException {URL myUrl = new URL(url);// 创建连接对象HttpsURLConnection connection = (HttpsURLConnection) myUrl.openConnection();connection.setRequestMethod(method);// 设置SSLSocketFactory对象（若不指定算法套，getSslContext().getSocketFactory()即可）connection.setSSLSocketFactory(new MySSLSocketFactory());// 验证hostname,全部允许connection.setHostnameVerifier((hostname, sslSession) -> true);// 设置通用请求属性connection.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.84 Safari/537.36");connection.setRequestProperty("Connection", "Keep-Alive");connection.setRequestProperty("Charset", "UTF-8");return connection;}public static void main(String[] args) throws Exception {String url = "https://***";httpsGet(url);
//        httpsPost(url, "username=admin&password=admin@1234&forceLogin=false");}
}

指定ssl算法套

如果是需要设置客户端算法套，可以通过继承SSLSocketFactory重写其createSocket()方法，自行设置SSL算法套。

import javax.net.ssl.*;
import java.io.IOException;
import java.net.InetAddress;
import java.net.Socket;
import java.security.KeyManagementException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;/*** 重写createSocket方法，设置算法套*/
public class MySSLSocketFactory extends SSLSocketFactory {private static final String[] cipherSuites = new String[]{"TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384","TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256"};private static SSLContext sslContext = null;// 设置算法套private void setSSLParams(SSLSocket sslSocket) {sslSocket.setUseClientMode(true);sslSocket.setEnabledCipherSuites(cipherSuites);}/*** 创建SSLContext对象，使用默认信任管理器初始化*/private static SSLContext getSslContext() {if (sslContext == null) {try {sslContext = SSLContext.getInstance("TLSv1.2");sslContext.init(new KeyManager[0], new TrustManager[]{new DefaultTrustManager()}, new SecureRandom());} catch (NoSuchAlgorithmException | KeyManagementException e) {e.printStackTrace();}SSLContext.setDefault(sslContext);}return sslContext;}@Overridepublic String[] getDefaultCipherSuites() {return cipherSuites;}@Overridepublic String[] getSupportedCipherSuites() {return cipherSuites;}@Overridepublic Socket createSocket(Socket socket, String host, int port, boolean b) throws IOException {SSLSocket sslSocket = (SSLSocket) getSslContext().getSocketFactory().createSocket(socket, host, port, b);setSSLParams(sslSocket);return sslSocket;}@Overridepublic Socket createSocket(String host, int port) throws IOException {SSLSocket sslSocket = (SSLSocket) getSslContext().getSocketFactory().createSocket(host, port);setSSLParams(sslSocket);return sslSocket;}@Overridepublic Socket createSocket(String host, int port, InetAddress localHost, int localPort) throws IOException {SSLSocket sslSocket = (SSLSocket) getSslContext().getSocketFactory().createSocket(host, port, localHost, localPort);setSSLParams(sslSocket);return sslSocket;}@Overridepublic Socket createSocket(InetAddress host, int port) throws IOException {SSLSocket sslSocket = (SSLSocket) getSslContext().getSocketFactory().createSocket(host, port);setSSLParams(sslSocket);return sslSocket;}@Overridepublic Socket createSocket(InetAddress address, int port, InetAddress localAddress, int localPort) throws IOException {SSLSocket sslSocket = (SSLSocket) getSslContext().getSocketFactory().createSocket(address, port, localAddress, localPort);setSSLParams(sslSocket);return sslSocket;}/*** SSL信任管理类*/private static class DefaultTrustManager implements X509TrustManager {@Overridepublic void checkClientTrusted(X509Certificate[] arg0, String arg1) throws CertificateException {}@Overridepublic void checkServerTrusted(X509Certificate[] arg0, String arg1) throws CertificateException {}@Overridepublic X509Certificate[] getAcceptedIssuers() {return null;}}}