java 实现文件内容的加密和解密

package com.umapp.test;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.Key;
import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
import javax.crypto.KeyGenerator;

public class TestDES {
  Key key;
  public TestDES(String str) {
    getKey(str);//生成密匙
  }
  /**
  * 根据参数生成KEY
  */
  public void getKey(String strKey) {
    try {
        KeyGenerator _generator = KeyGenerator.getInstance("DES");
        _generator.init(new SecureRandom(strKey.getBytes()));
        this.key = _generator.generateKey();
        _generator = null;
    } catch (Exception e) {
        throw new RuntimeException("Error initializing SqlMap class. Cause: " + e);
    }
  } 

  /**
  * 文件file进行加密并保存目标文件destFile中
  *
  * @param file   要加密的文件 如c:/test/srcFile.txt
  * @param destFile 加密后存放的文件名 如c:/加密后文件.txt
  */
  public void encrypt(String file, String destFile) throws Exception {
    Cipher cipher = Cipher.getInstance("DES");
    // cipher.init(Cipher.ENCRYPT_MODE, getKey());
    cipher.init(Cipher.ENCRYPT_MODE, this.key);
    InputStream is = new FileInputStream(file);
    OutputStream out = new FileOutputStream(destFile);
    CipherInputStream cis = new CipherInputStream(is, cipher);
    byte[] buffer = new byte[1024];
    int r;
    while ((r = cis.read(buffer)) > 0) {
        out.write(buffer, 0, r);
    }
    cis.close();
    is.close();
    out.close();
  }
  /**
  * 文件采用DES算法解密文件
  *
  * @param file 已加密的文件 如c:/加密后文件.txt
  *         * @param destFile
  *         解密后存放的文件名 如c:/ test/解密后文件.txt
  */
  public void decrypt(String file, String dest) throws Exception {
    Cipher cipher = Cipher.getInstance("DES");
    cipher.init(Cipher.DECRYPT_MODE, this.key);
    InputStream is = new FileInputStream(file);
    OutputStream out = new FileOutputStream(dest);
    CipherOutputStream cos = new CipherOutputStream(out, cipher);
    byte[] buffer = new byte[1024];
    int r;
    while ((r = is.read(buffer)) >= 0) {
    	System.out.println();
        cos.write(buffer, 0, r);
    }
    cos.close();
    out.close();
    is.close();
  }
  public static void main(String[] args) throws Exception {
    TestDES td = new TestDES("aaa");
    td.encrypt("e:/r.txt", "e:/r解密.txt"); //加密
    td.decrypt("e:/r解密.txt", "e:/r1.txt"); //解密 

  }
}