公钥使用X509EncodedKeySpec存储，但私有键使用PKCS8EncodedKeySpec。例如：

Public keys are stored using a X509EncodedKeySpec as you have, but Private keys use the PKCS8EncodedKeySpec. For example like this:

public static PrivateKey loadPrivateKey(String key64) throws GeneralSecurityException {
    byte[] clear = base64Decode(key64);
    PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(clear);
    KeyFactory fact = KeyFactory.getInstance("DSA");
    PrivateKey priv = fact.generatePrivate(keySpec);
    Arrays.fill(clear, (byte) 0);
    return priv;
}


public static PublicKey loadPublicKey(String stored) throws GeneralSecurityException {
    byte[] data = base64Decode(stored);
    X509EncodedKeySpec spec = new X509EncodedKeySpec(data);
    KeyFactory fact = KeyFactory.getInstance("DSA");
    return fact.generatePublic(spec);
}

public static String savePrivateKey(PrivateKey priv) throws GeneralSecurityException {
    KeyFactory fact = KeyFactory.getInstance("DSA");
    PKCS8EncodedKeySpec spec = fact.getKeySpec(priv,
            PKCS8EncodedKeySpec.class);
    byte[] packed = spec.getEncoded();
    String key64 = base64Encode(packed);

    Arrays.fill(packed, (byte) 0);
    return key64;
}


public static String savePublicKey(PublicKey publ) throws GeneralSecurityException {
    KeyFactory fact = KeyFactory.getInstance("DSA");
    X509EncodedKeySpec spec = fact.getKeySpec(publ,
            X509EncodedKeySpec.class);
    return base64Encode(spec.getEncoded());
}


public static void main(String[] args) throws Exception {
    KeyPairGenerator gen = KeyPairGenerator.getInstance("DSA");
    KeyPair pair = gen.generateKeyPair();

    String pubKey = savePublicKey(pair.getPublic());
    PublicKey pubSaved = loadPublicKey(pubKey);
    System.out.println(pair.getPublic()+"\n"+pubSaved);

    String privKey = savePrivateKey(pair.getPrivate());
    PrivateKey privSaved = loadPrivateKey(privKey);
    System.out.println(pair.getPrivate()+"\n"+privSaved);
}