从java中的密钥库文件中提取私钥

Question

我有一个密钥库文件，我有一些加密文本。我必须使用存储在密钥库文件中的私钥来解密它。我无法弄清楚如何在我的java方法中提取该私钥。

public void decrypt(String encryptedText) {
    byte[] decryptedData = null;  
    try { 
      FileInputStream is = new FileInputStream("/Users/rajat/workspace/dev/abc.jks");    
      KeyStore keystore = KeyStore.getInstance(KeyStore.getDefaultType());
      keystore.load(is, "abc".toCharArray());
      String alias = "xyz";
      Key key = keystore.getKey(alias, "abc".toCharArray());

      Cipher cipher = Cipher.getInstance("RSA");  
      cipher.init(Cipher.DECRYPT_MODE, key);  
      decryptedData = cipher.doFinal(encryptedText.getBytes());  
      System.out.println("Decrypted Data: " + new String(decryptedData));  
    } catch (Exception e) {  
     e.printStackTrace();  
    }   
  }

当我跑步时，我得到错误：

javax.crypto.IllegalBlockSizeException: Data must not be longer than 256 bytes
    at com.sun.crypto.provider.RSACipher.doFinal(RSACipher.java:337)
    at com.sun.crypto.provider.RSACipher.engineDoFinal(RSACipher.java:382)
    at javax.crypto.Cipher.doFinal(Cipher.java:2087)