java怎么给文件加密

1. 怎样用java给文件夹加密，拜求各位大侠！

一个例子
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.io.*;
import java.security.*;
import javax.crypto.*;
import javax.crypto.spec.*;

/**
文件名：FileEncrypter.java
JDK：1.40以上
说明：文件加密
加密方法：三重DES加密
加密过程：对选中的文件加密后在同文件夹下生成一个增加了".tdes"
扩展名的加密文件

解密过程：对选中的加密文件（必须有".tdes"扩展名）进行解密
*/
public class FileEncrypter extends JFrame{
public static final int WIDTH = 550;
public static final int HEIGHT = 200;

public static void main(String args[]) {
FileEncrypter fe = new FileEncrypter();
fe.show();
}

FileEncrypter(){
this.setSize(WIDTH,HEIGHT);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setResizable(false);
Toolkit tk = Toolkit.getDefaultToolkit();
Dimension screenSize = tk.getScreenSize();
this.setLocation((screenSize.width - WIDTH)/2,
(screenSize.height - HEIGHT)/2);
this.setTitle("文件加密器(TriDES)");
Container c = this.getContentPane();
c.setLayout( new FlowLayout());

final FilePanel fp = new FilePanel("文件选择");
c.add(fp);

final KeyPanel pp = new KeyPanel("密码");
c.add(pp);

JButton jbE = new JButton("加密");
c.add(jbE);
jbE.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent event){
File file = new File(fp.getFileName());
if (file.exists())
encrypt(file.getAbsoluteFile(),pp.getKey());
else
JOptionPane.showMessageDialog(
null,"请选择文件！","提示",JOptionPane.OK_OPTION);
}
});
JButton jbD = new JButton("解密");
c.add(jbD);
jbD.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent event){
File file = new File(fp.getFileName());
if (file.exists())
decrypt(file.getAbsoluteFile(),pp.getKey());
else
JOptionPane.showMessageDialog(
null,"请选择文件！","提示",JOptionPane.OK_OPTION);
}
});
}

/**
加密函数
输入：
要加密的文件，密码（由0-F组成，共48个字符，表示3个8位的密码）如：

其中：
AD67EA2F3BE6E5AD DES密码一
D368DFE03120B5DF DES密码二
92A8FD8FEC2F0746 DES密码三
输出：
对输入的文件加密后，保存到同一文件夹下增加了".tdes"扩展名的文件中。
*/
private void encrypt(File fileIn,String sKey){
try{
if(sKey.length() == 48){
byte[] bytK1 = getKeyByStr(sKey.substring(0,16));
byte[] bytK2 = getKeyByStr(sKey.substring(16,32));
byte[] bytK3 = getKeyByStr(sKey.substring(32,48));

FileInputStream fis = new FileInputStream(fileIn);
byte[] bytIn = new byte[(int)fileIn.length()];
for(int i = 0;i<fileIn.length();i++){
bytIn[i] = (byte)fis.read();
}
//加密
byte[] bytOut = encryptByDES(encryptByDES(
encryptByDES(bytIn,bytK1),bytK2),bytK3);
String fileOut = fileIn.getPath() + ".tdes";
FileOutputStream fos = new FileOutputStream(fileOut);
for(int i = 0;i<bytOut.length;i++){
fos.write((int)bytOut[i]);
}
fos.close();
JOptionPane.showMessageDialog(
this,"加密成功！","提示",JOptionPane.OK_OPTION);
}else
JOptionPane.showMessageDialog(
this,"密码长度必须等于48！","错误信息",JOptionPane.ERROR_MESSAGE);
}catch(Exception e){
e.printStackTrace();
}
}

/**
解密函数
输入：
要解密的文件，密码（由0-F组成，共48个字符，表示3个8位的密码）如：

其中：
AD67EA2F3BE6E5AD DES密码一
D368DFE03120B5DF DES密码二
92A8FD8FEC2F0746 DES密码三
输出：
对输入的文件解密后，保存到用户指定的文件中。
*/
private void decrypt(File fileIn,String sKey){
try{
if(sKey.length() == 48){
String strPath = fileIn.getPath();
if(strPath.substring(strPath.length()-5).toLowerCase().equals(".tdes"))
strPath = strPath.substring(0,strPath.length()-5);
else{
JOptionPane.showMessageDialog(
this,"不是合法的加密文件！","提示",JOptionPane.OK_OPTION);
return;
}
JFileChooser chooser = new JFileChooser();
chooser.setCurrentDirectory(new File("."));
chooser.setSelectedFile(new File(strPath));
//用户指定要保存的文件
int ret = chooser.showSaveDialog(this);
if(ret==JFileChooser.APPROVE_OPTION){

byte[] bytK1 = getKeyByStr(sKey.substring(0,16));
byte[] bytK2 = getKeyByStr(sKey.substring(16,32));
byte[] bytK3 = getKeyByStr(sKey.substring(32,48));

FileInputStream fis = new FileInputStream(fileIn);
byte[] bytIn = new byte[(int)fileIn.length()];
for(int i = 0;i<fileIn.length();i++){
bytIn[i] = (byte)fis.read();
}
//解密
byte[] bytOut = decryptByDES(decryptByDES(
decryptByDES(bytIn,bytK3),bytK2),bytK1);
File fileOut = chooser.getSelectedFile();
fileOut.createNewFile();
FileOutputStream fos = new FileOutputStream(fileOut);
for(int i = 0;i<bytOut.length;i++){
fos.write((int)bytOut[i]);
}
fos.close();
JOptionPane.showMessageDialog(
this,"解密成功！","提示",JOptionPane.OK_OPTION);
}
}else
JOptionPane.showMessageDialog(
this,"密码长度必须等于48！","错误信息",JOptionPane.ERROR_MESSAGE);
}catch(Exception e){
JOptionPane.showMessageDialog(
this,"解密失败，请核对密码！","提示",JOptionPane.OK_OPTION);
}
}

/**
用DES方法加密输入的字节
bytKey需为8字节长，是加密的密码
*/
private byte[] encryptByDES(byte[] bytP,byte[] bytKey) throws Exception{
DESKeySpec desKS = new DESKeySpec(bytKey);
SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");
SecretKey sk = skf.generateSecret(desKS);
Cipher cip = Cipher.getInstance("DES");
cip.init(Cipher.ENCRYPT_MODE,sk);
return cip.doFinal(bytP);
}

/**
用DES方法解密输入的字节
bytKey需为8字节长，是解密的密码
*/
private byte[] decryptByDES(byte[] bytE,byte[] bytKey) throws Exception{
DESKeySpec desKS = new DESKeySpec(bytKey);
SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");
SecretKey sk = skf.generateSecret(desKS);
Cipher cip = Cipher.getInstance("DES");
cip.init(Cipher.DECRYPT_MODE,sk);
return cip.doFinal(bytE);
}

/**
输入密码的字符形式，返回字节数组形式。
如输入字符串：AD67EA2F3BE6E5AD
返回字节数组：{ 173,103,234,47,59,230,229,173 }
*/
private byte[] getKeyByStr(String str){
byte[] bRet = new byte[str.length()/2];
for(int i=0;i<str.length()/2;i++){
Integer itg =
new Integer(16*getChrInt(str.charAt(2*i)) + getChrInt(str.charAt(2*i+1)));
bRet[i] = itg.byteValue();
}
return bRet;
}
/**
计算一个16进制字符的10进制值
输入：0-F
*/
private int getChrInt(char chr){
int iRet=0;
if(chr=="0".charAt(0)) iRet = 0;
if(chr=="1".charAt(0)) iRet = 1;
if(chr=="2".charAt(0)) iRet = 2;
if(chr=="3".charAt(0)) iRet = 3;
if(chr=="4".charAt(0)) iRet = 4;
if(chr=="5".charAt(0)) iRet = 5;
if(chr=="6".charAt(0)) iRet = 6;
if(chr=="7".charAt(0)) iRet = 7;
if(chr=="8".charAt(0)) iRet = 8;
if(chr=="9".charAt(0)) iRet = 9;
if(chr=="A".charAt(0)) iRet = 10;
if(chr=="B".charAt(0)) iRet = 11;
if(chr=="C".charAt(0)) iRet = 12;
if(chr=="D".charAt(0)) iRet = 13;
if(chr=="E".charAt(0)) iRet = 14;
if(chr=="F".charAt(0)) iRet = 15;
return iRet;
}
}

/**
文件选择组件。
*/
class FilePanel extends JPanel{
FilePanel(String str){
JLabel label = new JLabel(str);
JTextField fileText = new JTextField(35);
JButton chooseButton = new JButton("浏览...");
this.add(label);
this.add(fileText);
this.add(chooseButton);
clickAction ca = new clickAction(this);
chooseButton.addActionListener(ca);

}

public String getFileName(){
JTextField jtf = (JTextField)this.getComponent(1);
return jtf.getText();
}

private class clickAction implements ActionListener{
clickAction(Component c){
cmpt = c;
}

public void actionPerformed(ActionEvent event){
JFileChooser chooser = new JFileChooser();
chooser.setCurrentDirectory(new File("."));
int ret = chooser.showOpenDialog(cmpt);
if(ret==JFileChooser.APPROVE_OPTION){
JPanel jp = (JPanel)cmpt;
JTextField jtf = (JTextField)jp.getComponent(1);
jtf.setText(chooser.getSelectedFile().getPath());
}
}

private Component cmpt;
}
}

/**
密码生成组件。
*/
class KeyPanel extends JPanel{
KeyPanel(String str){
JLabel label = new JLabel(str);
JTextField fileText = new JTextField(35);
JButton chooseButton = new JButton("随机产生");
this.add(label);
this.add(fileText);
this.add(chooseButton);
clickAction ca = new clickAction(this);
chooseButton.addActionListener(ca);

}

//返回生成的密码（48个字符长度）
public String getKey(){
JTextField jtf = (JTextField)this.getComponent(1);
return jtf.getText();
}

private class clickAction implements ActionListener{
clickAction(Component c){
cmpt = c;
}

public void actionPerformed(ActionEvent event){
try{
KeyGenerator kg = KeyGenerator.getInstance("DES");
kg.init(56);
Key ke = kg.generateKey();
byte[] bytK1 = ke.getEncoded();
ke = kg.generateKey();
byte[] bytK2 = ke.getEncoded();
ke = kg.generateKey();
byte[] bytK3 = ke.getEncoded();

JPanel jp = (JPanel)cmpt;
JTextField jtf = (JTextField)jp.getComponent(1);
jtf.setText(getByteStr(bytK1)+getByteStr(bytK2)+getByteStr(bytK3));
}catch(Exception e){
e.printStackTrace();
}
}

private String getByteStr(byte[] byt){
String strRet = "";
for(int i=0;i<byt.length;i++){
//System.out.println(byt[i]);
strRet += getHexValue((byt[i]&240)/16);
strRet += getHexValue(byt[i]&15);
}
return strRet;
}

private String getHexValue(int s){
String sRet=null;
switch (s){
case 0: sRet = "0";break;
case 1: sRet = "1";break;
case 2: sRet = "2";break;
case 3: sRet = "3";break;
case 4: sRet = "4";break;
case 5: sRet = "5";break;
case 6: sRet = "6";break;
case 7: sRet = "7";break;
case 8: sRet = "8";break;
case 9: sRet = "9";break;
case 10: sRet = "A";break;
case 11: sRet = "B";break;
case 12: sRet = "C";break;
case 13: sRet = "D";break;
case 14: sRet = "E";break;
case 15: sRet = "F";
}
return sRet;
}

private Component cmpt;
}
}

2. 请问用java如何对文件进行加密解密

packagecom.palic.pss.afcs.worldthrough.common.util;

importjavax.crypto.Cipher;
importjavax.crypto.spec.SecretKeySpec;

importrepack.com.thoughtworks.xstream.core.util.Base64Encoder;
/**
*AES加密解密
*@authorEX-CHENQI004
*
*/
publicclassAesUtils{
		publicstaticfinalStringcKey="assistant7654321";
		/**
	*加密--把加密后的byte数组先进行二进制转16进制在进行base64编码
	*@paramsSrc
	*@paramsKey
	*@return
	*@throwsException
	*/
	publicstaticStringencrypt(StringsSrc,StringsKey)throwsException{
	if(sKey==null){
	("ArgumentsKeyisnull.");
	}
	if(sKey.length()!=16){
	(
	"ArgumentsKey'lengthisnot16.");
	}
	byte[]raw=sKey.getBytes("ASCII");
	SecretKeySpecskeySpec=newSecretKeySpec(raw,"AES");
	
	Ciphercipher=Cipher.getInstance("AES");
	cipher.init(Cipher.ENCRYPT_MODE,skeySpec);
	
	byte[]encrypted=cipher.doFinal(sSrc.getBytes("UTF-8"));
	StringtempStr=parseByte2HexStr(encrypted);
	
	Base64Encoderencoder=newBase64Encoder();
	returnencoder.encode(tempStr.getBytes("UTF-8"));
	}
	
	/**
	*解密--先进行base64解码，在进行16进制转为2进制然后再解码
	*@paramsSrc
	*@paramsKey
	*@return
	*@throwsException
	*/
	publicstaticStringdecrypt(StringsSrc,StringsKey)throwsException{
	
	if(sKey==null){
	("499");
	}
	if(sKey.length()!=16){
	("498");
	}
	
	byte[]raw=sKey.getBytes("ASCII");
	SecretKeySpecskeySpec=newSecretKeySpec(raw,"AES");
	
	Ciphercipher=Cipher.getInstance("AES");
	cipher.init(Cipher.DECRYPT_MODE,skeySpec);
	
	Base64Encoderencoder=newBase64Encoder();
	byte[]encrypted1=encoder.decode(sSrc);
	
	StringtempStr=newString(encrypted1,"utf-8");
	encrypted1=parseHexStr2Byte(tempStr);
	byte[]original=cipher.doFinal(encrypted1);
	StringoriginalString=newString(original,"utf-8");
	returnoriginalString;
	}
	
	/**
	*将二进制转换成16进制
	*
	*@parambuf
	*@return
	*/
	(bytebuf[]){
	StringBuffersb=newStringBuffer();
	for(inti=0;i<buf.length;i++){
	Stringhex=Integer.toHexString(buf[i]&0xFF);
	if(hex.length()==1){
	hex='0'+hex;
	}
	sb.append(hex.toUpperCase());
	}
	returnsb.toString();
	}
	
	/**
	*将16进制转换为二进制
	*
	*@paramhexStr
	*@return
	*/
	publicstaticbyte[]parseHexStr2Byte(StringhexStr){
	if(hexStr.length()<1)
	returnnull;
	byte[]result=newbyte[hexStr.length()/2];
	for(inti=0;i<hexStr.length()/2;i++){
	inthigh=Integer.parseInt(hexStr.substring(i*2,i*2+1),16);
	intlow=Integer.parseInt(hexStr.substring(i*2+1,i*2+2),
	16);
	result[i]=(byte)(high*16+low);
	}
	returnresult;
	}
	publicstaticvoidmain(String[]args)throwsException{
			/*
			*加密用的Key可以用26个字母和数字组成，最好不要用保留字符，虽然不会错，至于怎么裁决，个人看情况而定
			*/
			StringcKey="assistant7654321";
			//需要加密的字串
			StringcSrc="123456";
			//加密
			longlStart=System.currentTimeMillis();
			StringenString=encrypt(cSrc,cKey);
			System.out.println("加密后的字串是："+enString);
			longlUseTime=System.currentTimeMillis()-lStart;
			System.out.println("加密耗时："+lUseTime+"毫秒");
			//解密
			lStart=System.currentTimeMillis();
			StringDeString=decrypt(enString,cKey);
			System.out.println("解密后的字串是："+DeString);
			lUseTime=System.currentTimeMillis()-lStart;
			System.out.println("解密耗时："+lUseTime+"毫秒");
		}
}

3. 如何用java 将文件加密压缩为zip文件.

用java加密压缩zip文件：
package com.ninemax.demo.zip.decrypt;

import java.io.File;
import java.io.IOException;
import java.util.List;
import java.util.zip.DataFormatException;

import org.apache.commons.io.FileUtils;

import de.idyl.winzipaes.AesZipFileDecrypter;
import de.idyl.winzipaes.AesZipFileEncrypter;
import de.idyl.winzipaes.impl.AESDecrypter;
import de.idyl.winzipaes.impl.AESDecrypterBC;
import de.idyl.winzipaes.impl.AESEncrypter;
import de.idyl.winzipaes.impl.AESEncrypterBC;
import de.idyl.winzipaes.impl.ExtZipEntry;

/**
* 压缩指定文件或目录为ZIP格式压缩文件
* 支持中文(修改源码后)
* 支持密码(仅支持256bit的AES加密解密)
* 依赖bcprov项目(bcprov-jdk16-140.jar)
*
* @author zyh
*/
public class DecryptionZipUtil {

/**
* 使用指定密码将给定文件或文件夹压缩成指定的输出ZIP文件
* @param srcFile 需要压缩的文件或文件夹
* @param destPath 输出路径
* @param passwd 压缩文件使用的密码
*/
public static void zip(String srcFile,String destPath,String passwd) {
AESEncrypter encrypter = new AESEncrypterBC();
AesZipFileEncrypter zipFileEncrypter = null;
try {
zipFileEncrypter = new AesZipFileEncrypter(destPath, encrypter);
/**
* 此方法是修改源码后添加,用以支持中文文件名
*/
zipFileEncrypter.setEncoding("utf8");
File sFile = new File(srcFile);
/**
* AesZipFileEncrypter提供了重载的添加Entry的方法,其中:
* add(File f, String passwd)
* 方法是将文件直接添加进压缩文件
*
* add(File f, String pathForEntry, String passwd)
* 方法是按指定路径将文件添加进压缩文件
* pathForEntry - to be used for addition of the file (path within zip file)
*/
doZip(sFile, zipFileEncrypter, "", passwd);
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
zipFileEncrypter.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}

/**
* 具体压缩方法,将给定文件添加进压缩文件中,并处理压缩文件中的路径
* @param file 给定磁盘文件(是文件直接添加,是目录递归调用添加)
* @param encrypter AesZipFileEncrypter实例,用于输出加密ZIP文件
* @param pathForEntry ZIP文件中的路径
* @param passwd 压缩密码
* @throws IOException
*/
private static void doZip(File file, AesZipFileEncrypter encrypter,
String pathForEntry, String passwd) throws IOException {
if (file.isFile()) {
pathForEntry += file.getName();
encrypter.add(file, pathForEntry, passwd);
return;
}
pathForEntry += file.getName() + File.separator;
for(File subFile : file.listFiles()) {
doZip(subFile, encrypter, pathForEntry, passwd);
}
}

/**
* 使用给定密码解压指定压缩文件到指定目录
* @param inFile 指定Zip文件
* @param outDir 解压目录
* @param passwd 解压密码
*/
public static void unzip(String inFile, String outDir, String passwd) {
File outDirectory = new File(outDir);
if (!outDirectory.exists()) {
outDirectory.mkdir();
}
AESDecrypter decrypter = new AESDecrypterBC();
AesZipFileDecrypter zipDecrypter = null;
try {
zipDecrypter = new AesZipFileDecrypter(new File(inFile), decrypter);
AesZipFileDecrypter.charset = "utf-8";
/**
* 得到ZIP文件中所有Entry,但此处好像与JDK里不同,目录不视为Entry
* 需要创建文件夹,entry.isDirectory()方法同样不适用,不知道是不是自己使用错误
* 处理文件夹问题处理可能不太好
*/
List<ExtZipEntry> entryList = zipDecrypter.getEntryList();
for(ExtZipEntry entry : entryList) {
String eName = entry.getName();
String dir = eName.substring(0, eName.lastIndexOf(File.separator) + 1);
File extractDir = new File(outDir, dir);
if (!extractDir.exists()) {
FileUtils.forceMkdir(extractDir);
}
/**
* 抽出文件
*/
File extractFile = new File(outDir + File.separator + eName);
zipDecrypter.extractEntry(entry, extractFile, passwd);
}
} catch (IOException e) {
e.printStackTrace();
} catch (DataFormatException e) {
e.printStackTrace();
} finally {
try {
zipDecrypter.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}

/**
* 测试
* @param args
*/
public static void main(String[] args) {
/**
* 压缩测试
* 可以传文件或者目录
*/
// zip("M:\\ZIP\\test\\bb\\a\\t.txt", "M:\\ZIP\\test\\temp1.zip", "zyh");
// zip("M:\\ZIP\\test\\bb", "M:\\ZIP\\test\\temp2.zip", "zyh");

unzip("M:\\ZIP\\test\\temp2.zip", "M:\\ZIP\\test\\temp", "zyh");
}
}
压缩多个文件时，有两个方法(第一种没试)：
（1） 预先把多个文件压缩成zip，然后调用enc.addAll(inZipFile, password);方法将多个zip文件加进来。
（2）针对需要压缩的文件循环调用enc.add(inFile, password);，每次都用相同的密码。

4. 如何通过JAVA对电脑中的文本文档进行加密,最好能够详细的说一下！

package com.test.zc;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import javax.crypto.Cipher;

public class RSAEncrypt {

private KeyPairGenerator keyPairGen;

private KeyPair keyPair;

private RSAPrivateKey privateKey;

private RSAPublicKey publicKey;

public RSAEncrypt() {
try {
keyPairGen = KeyPairGenerator.getInstance("RSA");
keyPairGen.initialize(512);
keyPair = keyPairGen.generateKeyPair();
// Generate keys
privateKey = (RSAPrivateKey) keyPair.getPrivate();
publicKey = (RSAPublicKey) keyPair.getPublic();
} catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

public static void main(String[] args) {
RSAEncrypt encrypt = new RSAEncrypt();
File file = new File(
"C:\\Documents and Settings\\Administrator.DCB5E0D91E0D436\\桌面\\test.txt");
File newFile = new File(
"C:\\Documents and Settings\\Administrator.DCB5E0D91E0D436\\桌面\\test1.txt");
encrypt.encryptFile(encrypt, file, newFile);
File file1 = new File(
"C:\\Documents and Settings\\Administrator.DCB5E0D91E0D436\\桌面\\test1.txt");
File newFile1 = new File(
"C:\\Documents and Settings\\Administrator.DCB5E0D91E0D436\\桌面\\test2.txt");
encrypt.decryptFile(encrypt, file1, newFile1);
}

public void encryptFile(RSAEncrypt encrypt, File file, File newFile) {
try {
InputStream is = new FileInputStream(file);
OutputStream os = new FileOutputStream(newFile);

byte[] bytes = new byte[53];
while (is.read(bytes) > 0) {
byte[] e = encrypt.encrypt(encrypt.publicKey, bytes);
bytes = new byte[53];
os.write(e, 0, e.length);
}
os.close();
is.close();
System.out.println("write success");
} catch (Exception e) {
e.printStackTrace();
}
}

public void decryptFile(RSAEncrypt encrypt, File file, File newFile) {
try {
InputStream is = new FileInputStream(
new File(
"C:\\Documents and Settings\\Administrator.DCB5E0D91E0D436\\桌面\\test1.txt"));
OutputStream os = new FileOutputStream(
"C:\\Documents and Settings\\Administrator.DCB5E0D91E0D436\\桌面\\test2.txt");
byte[] bytes1 = new byte[64];
while (is.read(bytes1) > 0) {
byte[] de = encrypt.decrypt(encrypt.privateKey, bytes1);
bytes1 = new byte[64];
os.write(de, 0, de.length);
}
os.close();
is.close();
System.out.println("write success");

} catch (Exception e) {
e.printStackTrace();
}
}

/** */
/**
* * Encrypt String. *
*
* @return byte[]
*/
protected byte[] encrypt(RSAPublicKey publicKey, byte[] obj) {
if (publicKey != null) {
try {
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
return cipher.doFinal(obj);
} catch (Exception e) {
e.printStackTrace();
}
}
return null;
}

/** */
/**
* * Basic decrypt method *
*
* @return byte[]
*/
protected byte[] decrypt(RSAPrivateKey privateKey, byte[] obj) {
if (privateKey != null) {
try {
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.DECRYPT_MODE, privateKey);
return cipher.doFinal(obj);
} catch (Exception e) {
e.printStackTrace();
}
}
return null;
}
}

注意，RSAPrivateKey与RSAPublicKey在加密和解密中需保持一致，如果加密与解密需要分开进行，则需要把RSAPrivateKey与RSAPublicKey写入文件或其他方式保存进行解密

5. 如何用java实现文件（不只是txt文本）的整体加密解密

importjava.io.File;
importjava.io.FileInputStream;
importjava.io.FileOutputStream;
importjava.io.InputStream;
importjava.io.OutputStream;
importjava.security.KeyPair;
importjava.security.KeyPairGenerator;
importjava.security.NoSuchAlgorithmException;
importjava.security.interfaces.RSAPrivateKey;
importjava.security.interfaces.RSAPublicKey;
importjavax.crypto.Cipher;

/**
*文件加密解密
*加解密需要依靠以下四个属性，
	;
	staticKeyPairkeyPair;
	staticRSAPrivateKeyprivateKey;
	staticRSAPublicKeypublicKey;
*@authoryoung
*
*/
publicclassRSAEncrypt{

	;

	staticKeyPairkeyPair;

	staticRSAPrivateKeyprivateKey;

	staticRSAPublicKeypublicKey;

	static{
		try{
			//实例类型
			keyPairGen=KeyPairGenerator.getInstance("RSA");
			//初始化长度
			keyPairGen.initialize(512);
			//声场KeyPair
			keyPair=keyPairGen.generateKeyPair();
			//Generatekeys
			privateKey=(RSAPrivateKey)keyPair.getPrivate();
			publicKey=(RSAPublicKey)keyPair.getPublic();
		}catch(NoSuchAlgorithmExceptione){
			//TODOAuto-generatedcatchblock
			e.printStackTrace();
		}
	}

	publicstaticvoidmain(String[]args){
		RSAEncryptencrypt=newRSAEncrypt();
		Filefile=newFile(
				"C:\DocumentsandSettings\Administrator.DCB5E0D91E0D436\桌面\sdf.txt");
		FilenewFile=newFile(
				"C:\DocumentsandSettings\Administrator.DCB5E0D91E0D436\桌面\sdf1.txt");
		encrypt.encryptFile(encrypt,file,newFile);
		Filefile1=newFile(
				"C:\DocumentsandSettings\Administrator.DCB5E0D91E0D436\桌面\sdf1.txt");
		FilenewFile1=newFile(
				"C:\DocumentsandSettings\Administrator.DCB5E0D91E0D436\桌面\sdf2.txt");
		encrypt.decryptFile(encrypt,file1,newFile1);
	}

	/**
	*加密文件
	*@paramencryptRSAEncrypt对象
	*@paramfile源文件
	*@paramnewFile目标文件
	*/
	publicvoidencryptFile(RSAEncryptencrypt,Filefile,FilenewFile){
		try{
			InputStreamis=newFileInputStream(file);
			OutputStreamos=newFileOutputStream(newFile);

			byte[]bytes=newbyte[53];
			while(is.read(bytes)>0){
				byte[]e=encrypt.encrypt(RSAEncrypt.publicKey,bytes);
				bytes=newbyte[53];
				os.write(e,0,e.length);
			}
			os.close();
			is.close();
			System.out.println("writesuccess");
		}catch(Exceptione){
			e.printStackTrace();
		}
	}

	/**
	*解密文件
	*@paramencryptRSAEncrypt对象
	*@paramfile
	*@paramnewFile
	*/
	publicvoiddecryptFile(RSAEncryptencrypt,Filefile,FilenewFile){
		try{
			InputStreamis=newFileInputStream(file);
			OutputStreamos=newFileOutputStream(newFile);
			byte[]bytes1=newbyte[64];
			while(is.read(bytes1)>0){
				byte[]de=encrypt.decrypt(RSAEncrypt.privateKey,bytes1);
				bytes1=newbyte[64];
				os.write(de,0,de.length);
			}
			os.close();
			is.close();
			System.out.println("writesuccess");

		}catch(Exceptione){
			e.printStackTrace();
		}
	}

	/**
	*加密实现
	**EncryptString.*
	*
	*@returnbyte[]加密后的字节数组
	*/
	protectedbyte[]encrypt(RSAPublicKeypublicKey,byte[]obj){
		if(publicKey!=null){
			try{
				Ciphercipher=Cipher.getInstance("RSA");
				cipher.init(Cipher.ENCRYPT_MODE,publicKey);
				returncipher.doFinal(obj);
			}catch(Exceptione){
				e.printStackTrace();
			}
		}
		returnnull;
	}

	/**
	*解密实现
	**Basicdecryptmethod*
	*
	*@returnbyte[]解密后的字节数组
	*/
	protectedbyte[]decrypt(RSAPrivateKeyprivateKey,byte[]obj){
		if(privateKey!=null){
			try{
				Ciphercipher=Cipher.getInstance("RSA");
				cipher.init(Cipher.DECRYPT_MODE,privateKey);
				returncipher.doFinal(obj);
			}catch(Exceptione){
				e.printStackTrace();
			}
		}
		returnnull;
	}
}

6. java 对数据库properties文件加密

可以通过其它方法来实现：
1：如果没用框架，直接加密、解密即可
2：如果用hibernate之类，可以绕过Configuration，读取Hibernate配置文件解密后再连接数据库
3：考虑集群影响

7. 怎样为一个java程序加密 谢谢

只给编译后的.jar文件，不给.java文件

不过要说明的是，java因为是字节码，所以没有办法防止被反编译。
最多也就是做一下代码混淆，比如把方法或变量名改成无意义的名称，或者加一些完全无用的代码进去，让恶意攻击的人难以看懂