java获取https网站证书

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;  
 /**
  * 从网站获取java所需的证书，调用时传入域名。
  */
public class zs {  
  
    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);  
    }  
    }  
  
}