[code=java]
import java.io.File;
import java.io.FileInputStream;
import java.io.FileWriter;
import java.security.Key;
import java.security.KeyPair;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.UnrecoverableKeyException;
import java.security.cert.Certificate;

import sun.misc.*;

public class ExportPrivateKey {
private File keystoreFile;
private String keyStoreType;
private char[] password;
private String alias;
private File exportedFile;

public static KeyPair getPrivateKey(KeyStore keystore, String alias, char[] password) {
try {
Key key=keystore.getKey(alias,password);
if(key instanceof PrivateKey) {
Certificate cert=keystore.getCertificate(alias);
PublicKey publicKey=cert.getPublicKey();
return new KeyPair(publicKey,(PrivateKey)key);
}
} catch (UnrecoverableKeyException e) {
} catch (NoSuchAlgorithmException e) {
} catch (KeyStoreException e) {
}
return null;
}

public void export() throws Exception{
KeyStore keystore=KeyStore.getInstance(keyStoreType);
BASE64Encoder encoder=new BASE64Encoder();
keystore.load(new FileInputStream(keystoreFile),password);
KeyPair keyPair=getPrivateKey(keystore,alias,password);
PrivateKey privateKey=keyPair.getPrivate();
String encoded=encoder.encode(privateKey.getEncoded());
FileWriter fw=new FileWriter(exportedFile);
fw.write("—–BEGIN PRIVATE KEY—–\n");
fw.write(encoded);
fw.write("\n");
fw.write("—–END PRIVATE KEY—–");
fw.close();
}

public static void main(String args[]) throws Exception{
ExportPrivateKey export=new ExportPrivateKey();
export.keystoreFile=new File("/Users/Luke/Workspace/StringTest/src/com/lukejin/stringtest/keystore.jks");
export.keyStoreType="JKS";
export.password="changeit".toCharArray();
export.alias="tom_server";
export.exportedFile=new File("luke");
export.export();
}
}
[/code]

在eclipse中使用 import sun.misc.*;这个会报错的，可以先将这个的jar包移除，然后再添加下。就可以了