java IO 流加密解密小例子

一定要关流，完了。

import java.io.BufferedReader;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.OutputStream;

import java.security.InvalidKeyException;

import java.security.NoSuchAlgorithmException;

import javax.crypto.Cipher;

import javax.crypto.CipherInputStream;

import javax.crypto.CipherOutputStream;

import javax.crypto.NoSuchPaddingException;

import javax.crypto.SecretKey;

import javax.crypto.spec.SecretKeySpec;

public class T {

static String fileA = "D:/a.txt";

static String fileB = "D:/b.txt";

private static final byte[] KEY = { 37, -82, 88, -42, 1, -36, -104, -125,

4, 81, -75, -94, -33, -75, 110, -3, -32, 64, -48, -105, -43, -113,

104, 32 };

public static void main(String[] args) throws IOException,

InvalidKeyException, NoSuchAlgorithmException,

NoSuchPaddingException {

String sourceString = doReadNoDes(fileB);

doWrite(sourceString, fileA);

System.out.println(doRead(fileA));

}

private static String doRead(String file) throws InvalidKeyException,

NoSuchAlgorithmException, NoSuchPaddingException, IOException {

FileInputStream input = null;

try {

input = new FileInputStream(file);

return read(input);

} finally {

input.close();

}

}

private static void doWrite(String sourceString, String file)

throws IOException, InvalidKeyException, NoSuchAlgorithmException,

NoSuchPaddingException {

FileOutputStream output = null;

try {

output = new FileOutputStream(file);

write(output, sourceString);

} finally {

output.close();

}

}

private static String doReadNoDes(String file) throws IOException {

FileInputStream input = null;

try {

input = new FileInputStream(file);

return getStringFromStream(input);

} finally {

input.close();

}

}

private static String read(InputStream input)

throws NoSuchAlgorithmException, NoSuchPaddingException,

InvalidKeyException, IOException {

CipherInputStream cin = null;

try {

SecretKey key = getKey();

Cipher cp = Cipher.getInstance("DESede");

cp.init(Cipher.DECRYPT_MODE, key);

cin = new CipherInputStream(input, cp);

return getStringFromStream(cin);

} finally {

cin.close();

}

}

private static void write(OutputStream output, String sourceString)

throws IOException, NoSuchAlgorithmException,

NoSuchPaddingException, InvalidKeyException {

CipherOutputStream cin = null;

try {

SecretKey key = getKey();

Cipher cp = Cipher.getInstance("DESede");

cp.init(Cipher.ENCRYPT_MODE, key);

cin = new CipherOutputStream(output, cp);

cin.write(sourceString.getBytes());

} finally {

cin.close();

}

}

private static SecretKey getKey() {

return new SecretKeySpec(KEY, "DESede");

}

private static String getStringFromStream(InputStream stream) {

try {

BufferedReader in = new BufferedReader(

new InputStreamReader(stream));

StringBuffer buffer = new StringBuffer();

String line = null;

while ((line = in.readLine()) != null) {

buffer.append(line);

}

return buffer.toString();

} catch (IOException e) {

throw new RuntimeException(e);

}

}

}