本文主要討論的是java開發https請求ssl不受信任的解決方法，具體分析及實現代碼如下。
在java代碼中請求https鏈接的時候，可能會報下面這個錯誤
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 target
原因是沒有證書。在瀏覽器中直接使用url訪問是可以的，應該是瀏覽器之前就保存過對應的.cer證書。
解決方法有兩種，從目標機器獲得有效證書或者忽略證書信任問題。
一、獲得目標機器有效證書
1、編譯安裝證書程序javac InstallCert.java（代碼如下）
/* * Copyright 2006 Sun Microsystems, Inc. All Rights Reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * - Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * - Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * - Neither the name of Sun Microsystems nor the names of its * contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. *//** * http://blogs.sun.com/andreas/resource/InstallCert.java * Use: * java InstallCert hostname * Example: *% java InstallCert ecc.fedora.redhat.com */import javax.net.ssl.*;import java.io.*;import java.security.KeyStore;import java.security.MessageDigest;import java.security.cert.CertificateException;import java.security.cert.X509Certificate;/** * Class used to add the server's certificate to the KeyStore * with your trusted certificates. */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 <host>[: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);}}} 2、運行安裝證書程序生成證書
java InstallCert my.hoolai.com
例如： java InstalCert smtp.zhangsan.com:465 admin如果不加參數password和host的端口號，上面的獲取證書程序中默認給的端口號是：443，密碼是:changeit
3、根據運行提示信息，輸入1，回車，在當前目錄下生成名為： jssecacerts 的證書
將證書放置到$JAVA_HOME/jre/lib/security目錄下， 切記該JDK的jre是工程所用的環境！ ！ ！
或者：
System.setProperty("javax.net.ssl.trustStore", "你的jssecacerts证书路径");
可以更改密碼，在security目錄下運行命令
keytool -storepasswd -new xxxcom -keystore cacerts
就可以修改密碼，修改後使用命令
keytool -list -v -keystore cacerts
查看文件的信息，會提示需要密碼才能查看，如果輸入密碼與修改後的密碼匹配，說明修改成功了。
PS：至此這種方式可以成功使用ssl了，另外再補充一下，根據剛才生成的文件jssecacerts，可以生成cer文件，
命令如下
keytool -export -alias xxx.com-1 -keystore jssecacerts -rfc -file xxx.cer
如上，之前的工具類中默認命名別名是加上"-1"。使用InstallCert設置的密碼需要跟cacerts文件中的密碼一致，
如果修改過密碼，就需要修改InstallCert類中對應的密碼字符串，否則會有下面這個異常：
java.security.UnrecoverableKeyException: Password verification failed
二、忽略證書信任問題
源碼：http://mengyang.iteye.com/blog/575671
一定要注意需要在connection創建之前調用文章裡所述的方法，像這個樣子：
trustAllHttpsCertificates();HostnameVerifier hv = new HostnameVerifier() { public boolean verify(String urlHostName, SSLSession session) { return true; } };HttpsURLConnection.setDefaultHostnameVerifier(hv);connection = (HttpURLConnection) url.openConnection();好吧，兩種方法都試過有效。
總結
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