签字证书例子

  
import java.io.FileInputStream;       
import java.io.FileOutputStream;       
import java.io.IOException;       
import java.io.InputStream;       
import java.io.InputStreamReader;       
import java.io.PushbackReader;       
import java.security.KeyStore;       
import java.security.Principal;       
import java.security.PrivateKey;       
import java.security.cert.CertificateFactory;       
import java.security.cert.X509Certificate;       
import java.util.Arrays;       
      
import sun.security.x509.CertificateIssuerName;       
import sun.security.x509.X500Name;       
import sun.security.x509.X509CertImpl;       
import sun.security.x509.X509CertInfo;     
  
  
public class CertificateSigner {       
  public static void main(String[] args) {       
    String ksname = null; // the keystore name       
    String alias = null; // the private key alias       
    String inname = null; // the input file name       
    String outname = null; // the output file name       
    for (int i = 0; i < args.length; i += 2) {       
      if (args[i].equals("-keystore"))       
        ksname = args[i + 1];       
      else if (args[i].equals("-alias"))       
        alias = args[i + 1];       
      else if (args[i].equals("-infile"))       
        inname = args[i + 1];       
      else if (args[i].equals("-outfile"))       
        outname = args[i + 1];       
      else      
        usage();       
    }       
      
    if (ksname == null || alias == null || inname == null      
        || outname == null)       
      usage();       
      
    try {       
      PushbackReader console = new PushbackReader(new InputStreamReader(       
          System.in));       
      
      KeyStore store = KeyStore.getInstance("JKS", "SUN");       
      InputStream in = new FileInputStream(ksname);       
      char[] password = readPassword(console, "Keystore password");       
      store.load(in, password);       
      Arrays.fill(password, ' ');       
      in.close();       
      
      char[] keyPassword = readPassword(console, "Key password for "      
          + alias);       
      PrivateKey issuerPrivateKey = (PrivateKey) store.getKey(alias,       
          keyPassword);       
      Arrays.fill(keyPassword, ' ');       
      
      if (issuerPrivateKey == null)       
        error("No such private key");       
      
      in = new FileInputStream(inname);       
      
      CertificateFactory factory = CertificateFactory       
          .getInstance("X.509");       
      
      X509Certificate inCert = (X509Certificate) factory       
          .generateCertificate(in);       
      in.close();       
      byte[] inCertBytes = inCert.getTBSCertificate();       
      
      X509Certificate issuerCert = (X509Certificate) store       
          .getCertificate(alias);       
      Principal issuer = issuerCert.getSubjectDN();       
      String issuerSigAlg = issuerCert.getSigAlgName();       
      
      FileOutputStream out = new FileOutputStream(outname);       
      
      X509CertInfo info = new X509CertInfo(inCertBytes);       
      info.set(X509CertInfo.ISSUER, new CertificateIssuerName(       
          (X500Name) issuer));       
      
      X509CertImpl outCert = new X509CertImpl(info);       
      outCert.sign(issuerPrivateKey, issuerSigAlg);       
      outCert.derEncode(out);       
      
      out.close();       
    } catch (Exception exception) {       
      System.out.println(exception);       
    }       
  }       
      
  public static char[] readPassword(PushbackReader in, String prompt)       
      throws IOException {       
    System.out.print(prompt + ": ");       
    System.out.flush();       
    final int MAX_PASSWORD_LENGTH = 100;       
    int length = 0;       
    char[] buffer = new char[MAX_PASSWORD_LENGTH];       
      
    while (true) {       
      int ch = in.read();       
      if (ch == '\r' || ch == '\n' || ch == -1      
          || length == MAX_PASSWORD_LENGTH) {       
        if (ch == '\r') // handle DOS "\r\n" line ends       
        {       
          ch = in.read();       
          if (ch != '\n' && ch != -1)       
            in.unread(ch);       
        }       
        char[] password = new char[length];       
        System.arraycopy(buffer, 0, password, 0, length);       
        Arrays.fill(buffer, ' ');       
        return password;       
      } else {       
        buffer[length] = (char) ch;       
        length++;       
      }       
    }       
  }       
      
  public static void error(String message) {       
    System.out.println(message);       
    System.exit(1);       
  }       
      
  public static void usage() {       
    System.out.println("Usage: java CertificateSigner"      
        + " -keystore keyStore -alias issuerKeyAlias"      
        + " -infile inputFile -outfile outputFile");       
    System.exit(1);       
  }       
}