java程序实现对证书的操作

1 Java程序从证书文件读取证书

import java.io.*;
import java.security.cert.*; 
public class PrintCert{ 
public static void main(String args[ ]) throws Exception{
        CertificateFactory cf=CertificateFactory.getInstance("X.509"); 
        FileInputStream in=new FileInputStream("my.cer"); 
        Certificate c=cf.generateCertificate(in);
        in.close();
        String s=c.toString( );
        // 显示证书
        FileOutputStream fout=new FileOutputStream("tmp.txt");
         BufferedWriter out= new BufferedWriter(new OutputStreamWriter(fout));
       out.write(s,0,s.length( )); 
        out.close();   
}
}  
 2 Java程序从密钥库直接读取证书

import java.io.*;
import java.security.*;
import java.security.cert.Certificate;
public class PrintCert2{
    public static void main(String args[ ]) throws Exception{
          String pass="080302";
          String alias="mykey";
          String name=".keystore";
          FileInputStream in=new FileInputStream(name);
          KeyStore ks=KeyStore.getInstance("JKS");           
          ks.load(in,pass.toCharArray());
          Certificate c=ks.getCertificate(alias);
          in.close();
         System.out.println(c.toString( )); 
   }
 }  
3 Java程序显示证书指定信息（全名/公钥/签名等)

import java.io.*;
import java.security.*;
import java.security.cert.*;
import java.math.*;
public class ShowCertInfo{
   public static void main(String args[ ]) throws Exception{
        CertificateFactory cf=CertificateFactory.getInstance("X.509");
        FileInputStream in=new FileInputStream("my.cer");
        java.security.cert.Certificate c=cf.generateCertificate(in);
        in.close();
        X509Certificate t=(X509Certificate) c;
        System.out.println("版本号 "+t.getVersion());
        System.out.println("序列号 "+t.getSerialNumber().toString(16));
        System.out.println("全名 "+t.getSubjectDN());
        System.out.println("签发者全名n"+t.getIssuerDN());
        System.out.println("有效期起始日 "+t.getNotBefore());
        System.out.println("有效期截至日 "+t.getNotAfter());
        System.out.println("签名算法 "+t.getSigAlgName());
        byte[] sig=t.getSignature();
        System.out.println("签名n"+new BigInteger(sig).toString(16));
        PublicKey pk=t.getPublicKey();
        byte[ ] pkenc=pk.getEncoded();
        System.out.println("公钥");
        for(int i=0;i< div=""> 
        System.out.print(pkenc[i]+",");
        }
}
}

4 数字签名-对数字证书的数字签名

import java.io.*;
import java.security.*;
import java.security.cert.*;
import java.util.*;
import sun.security.x509.*;
/*
 * CA密钥库和其密码、CA中要使用的条目和其密码，新密钥库和其密码、新的条目名称
 * 特别注意：java中有些类得到特别保护（比如X509CertImpl），必须设置规则才能访问【项目属性-Java Build Path-JRE  
 * System Library-Access Rules-Edit-"sun/**"(Accessible)】
 */
public class SignCert{
    public static void main(String args[ ]) throws Exception{
        String signerName = "keystore/ibe"; 
        String signerAlias = "he";
        char[] signerStorePass = "080302".toCharArray( );
        char[] signerKeyPass = "080302".toCharArray( ); 
        String CertName = "cert/ibe-mao.cer";
        String newStore = "keystore/newstore";
        String newStoreAlias = "mao";
        char[] newStorePass = "080302".toCharArray();
        // CA证书
        FileInputStream in=new FileInputStream(signerName);
        KeyStore ks=KeyStore.getInstance("JKS");
        ks.load(in,signerStorePass);
        java.security.cert.Certificate c1=ks.getCertificate(signerAlias);
        PrivateKey caprk=(PrivateKey)ks.getKey(signerAlias,signerKeyPass);
        in.close();
        //得到签发者
        byte[] encod1=c1.getEncoded();
        X509CertImpl cimp1=new X509CertImpl(encod1);
        X509CertInfo cinfo1=(X509CertInfo)cimp1.get(X509CertImpl.NAME+"."+X509CertImpl.INFO);
        X500Name issuer=(X500Name)cinfo1.get(X509CertInfo.SUBJECT+"."+CertificateIssuerName.DN_NAME);
        //要签名的证书
        CertificateFactory cf=CertificateFactory.getInstance("X.509");
        FileInputStream in2=new FileInputStream(CertName);
        java.security.cert.Certificate c2=cf.generateCertificate(in2);
        in2.close();
        byte[] encod2=c2.getEncoded();
        X509CertImpl cimp2=new X509CertImpl(encod2);    
        X509CertInfo cinfo2=(X509CertInfo)cimp2.get(
        X509CertImpl.NAME+"."+X509CertImpl.INFO);
        //设置新证书有效期
        Date begindate =new Date();
        //60 day
        Date enddate =new Date(begindate.getTime()+3000*24*60*60*1000L);           
        CertificateValidity cv=new CertificateValidity(begindate,enddate);
        cinfo2.set(X509CertInfo.VALIDITY,cv);
        //设置新证书序列号
        int sn=(int)(begindate.getTime()/1000);
        CertificateSerialNumber csn=new CertificateSerialNumber(sn);
        cinfo2.set(X509CertInfo.SERIAL_NUMBER,csn);
        //设置新证书签发者
        cinfo2.set(X509CertInfo.ISSUER+"."+CertificateIssuerName.DN_NAME,issuer);
        //设置新证书算法
        AlgorithmId algorithm = new AlgorithmId(AlgorithmId.sha1WithRSAEncryption_oid);
        cinfo2.set(CertificateAlgorithmId.NAME+"."+CertificateAlgorithmId.ALGORITHM, algorithm);
        // 创建证书
        X509CertImpl newcert=new X509CertImpl(cinfo2);
        // 签名
        newcert.sign(caprk,"sha1WithRSA");
        //打印到控制台，验证一下信息
        System.out.println(newcert);
        // 存入密钥库
        ks.setCertificateEntry(newStoreAlias, newcert);
        FileOutputStream out=new FileOutputStream(newStore);
        ks.store(out,newStorePass);
        out.close();
    }
} 
注意：SignCert.java需要进行下面的处理才能正常导包。（eclipse把默认访问受限的api设成了error）
选中项目--右键--进入Properties(属性)视图
选中Java Build Path--点击Libraries--展开JRE System Library[JavaSE-1.6],选中Access rules这一项（如果没有，那就是JDK安装和配置的问题）。   
Edit--点击Add--在Rule Pattern（规则式样）编辑你允许导入的类库，如本例中输入(sun/**)，允许就是在Resolution选项中选中Accessible（当然，有些项目需要可以选择Forbidden、Discourage某些类库）。
然后重启就可以了。
5 验证CertPath证书链
验证CertPath证书链-CertPathValidator类基于TrustAnchor验证证书链
CertPathValidator类中的validate( )方法可以使用现成的PKIX certification path验证算法直接验证CertPath类型的对象。方法的第一个参数传入要验证的CertPath对象，第二个参数传入PKIXParameters类型的对象，它提供了验证时所使用的参数。
为了得到PKIXParameters类型的对象，必须指定最信任哪些CA。
ValidateCP.java
package cert;
import java.io.*;
import java.security.cert.*;
import java.security.cert.Certificate;
import java.util.*;
public class ValidateCP{          
    public static void main(String args[ ]) throws Exception{
        String[] arg=new String[]{"cert/ibe-mao-signed.cer","cert/ibe-he.cer"};
        String trustAnchor = "cert/ibe-he.cer";
        CertificateFactory cf = CertificateFactory.getInstance("X.509");
        int i;
        Listmylist = new ArrayList();
        for (i=0;i<arg.length;i++){
        FileInputStream in=new FileInputStream(arg[i]);
                Certificate c=cf.generateCertificate(in);
                mylist.add(c);
        }
        CertPath cp = cf.generateCertPath(mylist);
        //以上将证书列表转换成证书链
        //设置锚点
        FileInputStream in=new FileInputStream(trustAnchor);
        Certificate trust=cf.generateCertificate(in);
        // Create TrustAnchor
        TrustAnchor anchor = new TrustAnchor( (X509Certificate)trust,null);
        // Set the PKIX parameters
        PKIXParameters params = new PKIXParameters(Collections.singleton(anchor));
        params.setRevocationEnabled(false);
        CertPathValidator cpv = CertPathValidator.getInstance("PKIX");
        try {
         PKIXCertPathValidatorResult result =(PKIXCertPathValidatorResult) cpv.validate(cp, params);
         System.out.println(result);
         System.out.println(result.getTrustAnchor());
        } catch (CertPathValidatorException cpve) {
         System.out.println("Validation failure, cert[" + cpve.getIndex() + "] :" + cpve.getMessage());
        }
 }
}