java实现重要信息的加密解密(模拟信用卡号的保存)

package cn.felay.io;

import java.io.Externalizable;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectInputStream;
import java.io.ObjectOutput;
import java.io.ObjectOutputStream;
import java.security.InvalidKeyException;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.KeyGenerator;
import javax.crypto.spec.SecretKeySpec;

/**
 * 自定义序列化对象信息(加密保存重要信息)
 *
 * @author <a mailto:[email protected]>felayman</a>
 * @timer 2014年6月10日 下午8:10:29
 */
public class ExternalizableDemo {

	public static void main(String[] args) {
		Customer customer;
		try {
			// 构造一个信用卡用户
			customer = new Customer(1, "1234-5678-9876");
			// 打印加密前的信用卡信息
			System.out.println("before saving object:");
			System.out.println("ID:" + customer.getId() + ",CC:"
					+ customer.getCreditCard());
			// 创建对象输出流,该流是给予文件输出流的,即该流的数据是从文件中获取的,下面两行代码表示创建一个写入到指定文件的对象输出流
			ObjectOutputStream outStream = new ObjectOutputStream(
					new FileOutputStream("src/res/customer.dat"));
			// 将创建号的信用卡用户保存到customer.dat文件中
			outStream.writeObject(customer);
			outStream.close();// 关闭流
			// 创建一个从指定文件读取内容的输入流
			ObjectInputStream inputStream = new ObjectInputStream(
					new FileInputStream("src/res/customer.dat"));
			// 将读取的对象保存到
			customer = (Customer) inputStream.readObject();
			System.out.println("after retreieving object");// 输出解密后的对象信息
			System.out.println("ID:" + customer.getId() + ",CC:"
					+ customer.getCreditCard());
			inputStream.close();
		} catch (IOException e) {
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}

	}
}

class Customer implements Externalizable {

	private int id; // ID号
	private String creditCard; // 信用卡号
	private static Cipher cipher; // 加密和解密
	private static SecretKeySpec secretKeySpec; // 密钥

	public Customer() {
		this.id = 0;
		this.creditCard = "";
	}

	// 该实例保存用户的id号和信用卡号
	public Customer(int id, String creditCard) {
		this.id = id;
		this.creditCard = creditCard;
	}

	static {
		try {
			createCipher(); // 创建一个加密解密机
		} catch (Exception e) {
			e.printStackTrace();
			System.out.println("加密过程出现错误");
			System.exit(1);
		}
	}

	public int getId() {
		return this.id;
	}

	private static void createCipher() throws Exception {
		KeyGenerator kgen = KeyGenerator.getInstance("AES");// Rijndael加密算法
		kgen.init(128); // 指定生成的密钥长度为128位
		SecretKeySpec skey = (SecretKeySpec) kgen.generateKey();// 根据Rijndael加密算法生成一个密钥,并将密钥以字节数组方式保存到SecretKeySpec对象中
		byte[] raw = skey.getEncoded();// 将生成的密钥保存到字节数组中
		secretKeySpec = new SecretKeySpec(raw, "AES");// 密钥转换,将上述的密钥保存到Customer类的属性中,防止失效
		cipher = Cipher.getInstance("AES");// 将算法密钥保存到该对象中以实现解密功能
	}

	public String getCreditCard() {
		return this.creditCard;
	}

	public static Cipher getCipher() {
		return cipher;
	}

	public static SecretKeySpec getSecretKeySpec() {
		return secretKeySpec;
	}

	// 保存密钥
	@Override
	public void writeExternal(ObjectOutput out) throws IOException {
		try {
			out.write(this.id);
			this.encript();
			out.writeUTF(this.creditCard);
			System.out.println("after encryption:");// 加密后
			System.out.println("id:" + this.id + ",CC:" + this.creditCard);
		} catch (InvalidKeyException | IllegalBlockSizeException
				| BadPaddingException e) {
			e.printStackTrace();
		}
	}

	// 读取密钥
	@Override
	public void readExternal(ObjectInput in) throws IOException,
			ClassNotFoundException {
		this.id = in.read();
		String str = in.readUTF();
		this.decrypt(str);
	}

	// 加密
	private void encript() throws InvalidKeyException,
			IllegalBlockSizeException, BadPaddingException {
		cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec);
		byte[] buff = cipher.doFinal(this.creditCard.getBytes());
		this.creditCard = new String(buff);
	}

	// 解密
	private void decrypt(String str) {
		try {
			cipher.init(Cipher.DECRYPT_MODE, secretKeySpec);
			byte[] buff = cipher.doFinal(str.getBytes());
			this.creditCard = new String(buff);
		} catch (InvalidKeyException | IllegalBlockSizeException
				| BadPaddingException e) {
			e.printStackTrace();
		}

	}

}

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