方法一(修改cacerts文件)
java 把证书都放在了 D:\jdks\1.8\jre\lib\security 这个路径下的cacerts 文件里面。
我们进入jdk/bin这个路径，使用keytool工具。
输入以下命令 keytool -import -aliias [证书名字] -keystore [cacerts路径] -file [证书地址] 即可。
keytool -import -alias clientkey -file C:\ssl\xxx.pem -keystore D:\jdks\1.8\jre\lib\security\cacerts -trustcacerts如果是自己的网站可以从服务商那里下载，如果是别人的网站那么需要从浏览器导出。
或者到方法二那里通过代码生成证书。
接下来输入密钥口令：changeit 。提示是否信任证书的时候输入y，即可成功导入。
后续注意：
最后需要注意的是，证书是有时间限制的。记得看下证书的到期时间，下次还是需要更新的。
删除原来的证书，更新新证书的方法：
展示所有证书
keytool -list -keystore cacerts
删除指定证书
keytool -delete -alias akazam_email -keystore cacerts
重新添加新证书
keytool -import -alias akazam_email -file akazam_email.cer -keystore cacerts -trustcacerts
原文：用HttpClient请求对方网站数据报unable to find valid certification path to requested target_xfjs
方法二(新增jssecacerts证书文件)
首先也是下载访问的SSL站点的证书。
写一个安全程序专门用于获取安全证书：
import java.io.*;import java.net.URL; import java.security.*;import java.security.cert.*; import javax.net.ssl.*; public class InstallCert { public static void main(String[] args) throws Exception { 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 = "0123456789abcdef".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); } } } 将代码保存为InstallCert.java文件，并通过javac InstallCert.java 命令编译Java程序
执行 java InstallCert hostname 命令，如：java InstallCert 192.168.1.137:8443（要访问的目标程序的IP地址和端口）或者是java InstallCert baidu.com:443，然后会看到如下信息：
java InstallCert ecc.fedora.redhat.comLoading KeyStore /usr/jdk/instances/jdk1.5.0/jre/lib/security/cacerts...Opening connection to ecc.fedora.redhat.com:443...Starting SSL handshake... javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested targetat com.sun.net.ssl.internal.ssl.Alerts.getSSLException(Alerts.java:150)at com.sun.net.ssl.internal.ssl.SSLSocketImpl.fatal(SSLSocketImpl.java:1476)at com.sun.net.ssl.internal.ssl.Handshaker.fatalSE(Handshaker.java:174)at com.sun.net.ssl.internal.ssl.Handshaker.fatalSE(Handshaker.java:168)at com.sun.net.ssl.internal.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:846)at com.sun.net.ssl.internal.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:106)at com.sun.net.ssl.internal.ssl.Handshaker.processLoop(Handshaker.java:495)at com.sun.net.ssl.internal.ssl.Handshaker.process_record(Handshaker.java:433)at com.sun.net.ssl.internal.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:815)at com.sun.net.ssl.internal.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1025)at com.sun.net.ssl.internal.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1038)at InstallCert.main(InstallCert.java:63)Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested targetat sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:221)at sun.security.validator.PKIXValidator.engineValidate(PKIXValidator.java:145)at sun.security.validator.Validator.validate(Validator.java:203)at com.sun.net.ssl.internal.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:172)at InstallCert$SavingTrustManager.checkServerTrusted(InstallCert.java:158)at com.sun.net.ssl.internal.ssl.JsseX509TrustManager.checkServerTrusted(SSLContextImpl.java:320)at com.sun.net.ssl.internal.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:839)... 7 moreCaused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested targetat sun.security.provider.certpath.SunCertPathBuilder.engineBuild(SunCertPathBuilder.java:236)at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:194)at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:216)... 13 more Server sent 2 certificate(s): 1 Subject CN=ecc.fedora.redhat.com, O=example.com, C=US Issuer CN=Certificate Shack, O=example.com, C=US sha1 2e 7f 76 9b 52 91 09 2e 5d 8f 6b 61 39 2d 5e 06 e4 d8 e9 c7 md5 dd d1 a8 03 d7 6c 4b 11 a7 3d 74 28 89 d0 67 54 2 Subject CN=Certificate Shack, O=example.com, C=US Issuer CN=Certificate Shack, O=example.com, C=US sha1 fb 58 a7 03 c4 4e 3b 0e e3 2c 40 2f 87 64 13 4d df e1 a1 a6 md5 72 a0 95 43 7e 41 88 18 ae 2f 6d 98 01 2c 89 68 Enter certificate to add to trusted keystore or 'q' to quit: [1]直接输入1，然后会在相应的目录下产生一个名为‘jssecacerts’的证书，将证书copy到$JAVA_HOME/jre/lib/security目录下，
或者通过执行：
System.setProperty("javax.net.ssl.trustStore", "D:\\UTA\\DOC_E_Health_XML\\Keystore\\jssecacerts重启程序即可解决。
来源：解决 sun.security.validator.ValidatorException: PKIX path building failed
来源地址：https://blog.csdn.net/qq_34626094/article/details/128917682
