我测试的字符串是JQuery源码。

明文长度:78082
压缩后：26566
加密长度：54746
再压缩:41647
-----------------------------
密文长度:41647
解压缩：54746
解密后：26566
再解压：78082
-----------------------------
比对成功

Des需要Jar：sun.misc.BASE64Decoder.jar

Test
复制代码 代码如下:
public static void main(String[] args) throws Exception {
String cont = "";
String cont2=jm(yjy(cont));
if(cont.equals(cont2)){
System.out.println("比对成功");
}else{
System.out.println("比对失败");
}
}

public static String yjy(String cont) throws Exception {
System.out.println("明文长度:" + cont.length());
// 第一次压缩
cont = ZipUtil2.compress(cont);
System.out.println("压缩后：" + cont.length());
// 第一次加密
cont = DesUtil.encrypt(cont, DesUtil.PWD_KEY);
System.out.println("加密长度：" + cont.length());
// 第二次压缩
cont = ZipUtil2.compress(cont);
System.out.println("再压缩:" + cont.length());
return cont;
}

public static String jm(String cont) throws Exception {
System.out.println("-----------------------------");
System.out.println("密文长度:" + cont.length());

// 第一次解压缩
cont = ZipUtil2.uncompress(cont);
System.out.println("解压缩：" + cont.length());

// 第一次解密
cont = DesUtil.decrypt(cont, DesUtil.PWD_KEY);
System.out.println("解密后：" + cont.length());

// 第二次解压缩
cont = ZipUtil2.uncompress(cont);
System.out.println("再解压：" + cont.length());

return cont;
}

DesUtil

复制代码 代码如下:
import java.io.IOException;
import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;

import Decoder.BASE64Decoder;
import Decoder.BASE64Encoder;

public class DesUtil {

private final static String DES = "DES";
public final static String PWD_KEY = "MZTHPWDJM";
public final static String ID_KEY = "MZTHIDJM";

public static void main(String[] args) throws Exception {
String data = "xkajsdasdk'al;ks'dl;kasl;d";
System.err.println("加密："+encrypt(data, PWD_KEY));
System.err.println("解密：" +decrypt(encrypt(data, PWD_KEY), PWD_KEY));
}

/**
* Description 根据键值进行加密
*
* @param data
* @param key
* 加密键byte数组
* @return
* @throws Exception
*/
public static String encrypt(String data, String key) throws Exception {
byte[] bt = encrypt(data.getBytes(), key.getBytes());
String strs = new BASE64Encoder().encode(bt);
return strs;
}

/**
* Description 根据键值进行解密
*
* @param data
* @param key
* 加密键byte数组
* @return
* @throws IOException
* @throws Exception
*/
public static String decrypt(String data, String key) throws IOException,
Exception {
if (data == null)
return null;
BASE64Decoder decoder = new BASE64Decoder();
byte[] buf = decoder.decodeBuffer(data);
byte[] bt = decrypt(buf, key.getBytes());
return new String(bt);
}

/**
* Description 根据键值进行加密
*
* @param data
* @param key
* 加密键byte数组
* @return
* @throws Exception
*/
private static byte[] encrypt(byte[] data, byte[] key) throws Exception {
// 生成一个可信任的随机数源
SecureRandom sr = new SecureRandom();

// 从原始密钥数据创建DESKeySpec对象
DESKeySpec dks = new DESKeySpec(key);

// 创建一个密钥工厂，然后用它把DESKeySpec转换成SecretKey对象
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(DES);
SecretKey securekey = keyFactory.generateSecret(dks);

// Cipher对象实际完成加密操作
Cipher cipher = Cipher.getInstance(DES);

// 用密钥初始化Cipher对象
cipher.init(Cipher.ENCRYPT_MODE, securekey, sr);

return cipher.doFinal(data);
}

/**
* Description 根据键值进行解密
*
* @param data
* @param key
* 加密键byte数组
* @return
* @throws Exception
*/
private static byte[] decrypt(byte[] data, byte[] key) throws Exception {
// 生成一个可信任的随机数源
SecureRandom sr = new SecureRandom();

// 从原始密钥数据创建DESKeySpec对象
DESKeySpec dks = new DESKeySpec(key);

// 创建一个密钥工厂，然后用它把DESKeySpec转换成SecretKey对象
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(DES);
SecretKey securekey = keyFactory.generateSecret(dks);

// Cipher对象实际完成解密操作
Cipher cipher = Cipher.getInstance(DES);

// 用密钥初始化Cipher对象
cipher.init(Cipher.DECRYPT_MODE, securekey, sr);

return cipher.doFinal(data);
}
}

ZipUtil2
.
复制代码 代码如下:
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;

// 将一个字符串按照zip方式压缩和解压缩
public class ZipUtil2 {

// 测试方法
public static void main(String[] args) throws IOException {

// 测试字符串
String str = "";
System.out.println("原长度：" + str.length());
System.out.println("压缩后：" + ZipUtil2.compress(str).length());
System.out
.println("解压缩：" + ZipUtil2.uncompress(ZipUtil2.compress(str)));
}

// 压缩
public static String compress(String str) throws IOException {
if (str == null || str.length() == 0) {
return str;
}
ByteArrayOutputStream out = new ByteArrayOutputStream();
GZIPOutputStream gzip = new GZIPOutputStream(out);
gzip.write(str.getBytes());
gzip.close();
return out.toString("ISO-8859-1");
}

// 解压缩
public static String uncompress(String str) throws IOException {
if (str == null || str.length() == 0) {
return str;
}
ByteArrayOutputStream out = new ByteArrayOutputStream();
ByteArrayInputStream in = new ByteArrayInputStream(
str.getBytes("ISO-8859-1"));
GZIPInputStream gunzip = new GZIPInputStream(in);
byte[] buffer = new byte[256];
int n;
while ((n = gunzip.read(buffer)) >= 0) {
out.write(buffer, 0, n);
}
// toString()使用平台默认编码，也可以显式的指定如toString("GBK")
return out.toString();
}

}