这个问题的全称是：unable to find valid certification path to requested target原因是：缺少安全证书。
方法/步骤
2package test.keystore;import java.io.BufferedReader;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.InputStream;import java.io.InputStreamReader;import java.io.OutputStream;import java.security.KeyStore;import java.security.MessageDigest;import java.security.cert.CertificateException;import java.security.cert.X509Certificate;import javax.net.ssl.SSLContext;import javax.net.ssl.SSLException;import javax.net.ssl.SSLSocket;import javax.net.ssl.SSLSocketFactory;import javax.net.ssl.TrustManager;import javax.net.ssl.TrustManagerFactory;import javax.net.ssl.X509TrustManager;/** * 安装证书 * * @author 单红宇(365384722) * @myblog http://blog.csdn.net/catoop/ * @create 2016年4月14日 */public class InstallCert { // 我们要访问的HTTPS服务，如访问 https://www.shanhy.com public static final String hostName = 'www.bttt.la'; public static void main(String[] args) throws Exception { args = new String[]{hostName}; String host; int port; char[] passphrase; if ((args.length == 1) || (args.length == 2)) { String[] c = args[0].split(':'); host = c[0]; port = (c.length == 1) ? 443 : Integer.parseInt(c[1]); String p = (args.length == 1) ? 'changeit' : args[1]; passphrase = p.toCharArray(); } else { System.out.println('Usage: java InstallCert [:port] [passphrase]'); return; } File file = new File('jssecacerts'); if (file.isFile() == false) { char SEP = File.separatorChar; File dir = new File(System.getProperty('java.home') + SEP + 'lib' + SEP + 'security'); file = new File(dir, 'jssecacerts'); if (file.isFile() == false) { file = new File(dir, 'cacerts'); } } System.out.println('Loading KeyStore ' + file + '...'); InputStream in = new FileInputStream(file); KeyStore ks = KeyStore.getInstance(KeyStore.getDefaultType()); ks.load(in, passphrase); in.close(); SSLContext context = SSLContext.getInstance('TLS'); TrustManagerFactory tmf = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm()); tmf.init(ks); X509TrustManager defaultTrustManager = (X509TrustManager) tmf.getTrustManagers()[0]; SavingTrustManager tm = new SavingTrustManager(defaultTrustManager); context.init(null, new TrustManager[] { tm }, null); SSLSocketFactory factory = context.getSocketFactory(); System.out.println('Opening connection to ' + host + ':' + port + '...'); SSLSocket socket = (SSLSocket) factory.createSocket(host, port); socket.setSoTimeout(10000); try { System.out.println('Starting SSL handshake...'); socket.startHandshake(); socket.close(); System.out.println(); System.out.println('No errors, certificate is already trusted'); } catch (SSLException e) { System.out.println(); e.printStackTrace(System.out); } X509Certificate[] chain = tm.chain; if (chain == null) { System.out.println('Could not obtain server certificate chain'); return; } BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); System.out.println(); System.out.println('Server sent ' + chain.length + ' certificate(s):'); System.out.println(); MessageDigest sha1 = MessageDigest.getInstance('SHA1'); MessageDigest md5 = MessageDigest.getInstance('MD5'); for (int i = 0; i < chain.length; i++) { X509Certificate cert = chain[i]; System.out.println(' ' + (i + 1) + ' Subject ' + cert.getSubjectDN()); System.out.println(' Issuer ' + cert.getIssuerDN()); sha1.update(cert.getEncoded()); System.out.println(' sha1 ' + toHexString(sha1.digest())); md5.update(cert.getEncoded()); System.out.println(' md5 ' + toHexString(md5.digest())); System.out.println(); } System.out.println('Enter certificate to add to trusted keystore or 'q' to quit: [1]'); String line = reader.readLine().trim(); int k; try { k = (line.length() == 0) ? 0 : Integer.parseInt(line) - 1; } catch (NumberFormatException e) { System.out.println('KeyStore not changed'); return; } X509Certificate cert = chain[k]; String alias = host + '-' + (k + 1); ks.setCertificateEntry(alias, cert); OutputStream out = new FileOutputStream('jssecacerts'); ks.store(out, passphrase); out.close(); System.out.println(); System.out.println(cert); System.out.println(); System.out.println('Added certificate to keystore 'jssecacerts' using alias '' + alias + '''); } private static final char[] HEXDIGITS = 'abcdef'.toCharArray(); private static String toHexString(byte[] bytes) { StringBuilder sb = new StringBuilder(bytes.length * 3); for (int b : bytes) { b &= 0xff; sb.append(HEXDIGITS[b >> 4]); sb.append(HEXDIGITS[b & 15]); sb.append(' '); } return sb.toString(); } private static class SavingTrustManager implements X509TrustManager { private final X509TrustManager tm; private X509Certificate[] chain; SavingTrustManager(X509TrustManager tm) { this.tm = tm; } public X509Certificate[] getAcceptedIssuers() { throw new UnsupportedOperationException(); } public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException { throw new UnsupportedOperationException(); } public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException { this.chain = chain; tm.checkServerTrusted(chain, authType); } }}
4然后输入1并回车，也会打印一些信息，然后文件就生成了。我是在eclipse中运行的，生成的证书是在workspace中的项目目录中文件名：jssecacerts
5复制该文件到%JAVA_HONME%\\jre\\lib\\security\\目录中。jssecacerts 其实是一个证书库，根据上面的代码生成后里面只有一个网站的证书，如果还要加入其它网站的证书，需要要到java keytool命令
6keytool -import -alias 别名 -file cer证书路径 -keystore '/usr/lib/jdk1.8/jre/lib/security/jssecacerts'执行之后会让输入密码：默认是changeit
7查看：keytool -list -keystore '/usr/lib/jdk1.8/jre/lib/security/jssecacerts' | findstr /i 别名在linux 下 findstr命令好像不管用，只知道是这样用，也不是很明白其中的原理，也希望知道的朋友可以指导一下
