Java从证书库文件中导出RSA公钥私钥

RSA的证书的生成，见博文：http://blog.csdn.net/yx0628/article/details/78421017

下面是Java从证书库keystore文件，及证书cer文件中提取私钥，公钥的示例代码：

import java.io.FileInputStream;
import java.security.KeyStore;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;

import sun.misc.BASE64Encoder;

public class Demo {

	public static void main(String[] args) throws Exception {

		String cerPath = "D:/mypublickey.cer";		//证书文件路径
		String storePath = "D:/mykeystore.keystore";	//证书库文件路径
		String alias = "mykey";		//证书别名
		String storePw = "123456";	//证书库密码
		String keyPw = "123456";	//证书密码

		System.out.println("从证书获取的公钥为:" + getPublicKey(cerPath));
		System.out.println("从证书获取的私钥为:" + getPrivateKey(storePath, alias, storePw, keyPw));

	}

	
	private static String getPublicKey(String cerPath) throws Exception {
		CertificateFactory certificatefactory = CertificateFactory.getInstance("X.509");
		FileInputStream fis = new FileInputStream(cerPath);
		X509Certificate Cert = (X509Certificate) certificatefactory.generateCertificate(fis);
		PublicKey pk = Cert.getPublicKey();
		String publicKey = new BASE64Encoder().encode(pk.getEncoded());
		return publicKey;
	}

	private static String getPrivateKey(String storePath, String alias, String storePw, String keyPw) throws Exception {
		FileInputStream is = new FileInputStream(storePath);
		KeyStore ks = KeyStore.getInstance("JKS");
		ks.load(is, storePw.toCharArray());
		is.close();
		PrivateKey key = (PrivateKey) ks.getKey(alias, keyPw.toCharArray());
		System.out.println("privateKey:" + new BASE64Encoder().encode(key.getEncoded()));
		String privateKey = new BASE64Encoder().encode(key.getEncoded());
		return privateKey;
	}

}

运行结果：可以看到公钥和私钥，私钥自己保存好即可。