java 实现文件内容的加密和解密

转载： http://xiaoxiaokuang.iteye.com/blog/1440031

留作备用，直接代码

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 
    
  } 
}