扩展Spring——外部属性文件安全（二）

编写支持加密属性文件的实现类
    通过以上分析，我们设计一个支持加密属性文件的增强型PropertyPlaceholderConfigurer，其代码如所示：
代码清单 2

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.security.Key;
import java.util.Properties;
import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer;
import org.springframework.core.io.Resource;
import org.springframework.util.DefaultPropertiesPersister;
import org.springframework.util.PropertiesPersister;
public class DecryptPropertyPlaceholderConfigurer
        extends PropertyPlaceholderConfigurer ...{
    private Resource[] locations;   //① 重新定义父类中的这个同名属性
    private Resource keyLocation; //② 用于指定密钥文件
    public void setKeyLocation(Resource keyLocation) ...{
        this.keyLocation = keyLocation;
    }
    public void setLocations(Resource[] locations) ...{
        this.locations = locations;
    }
    public void loadProperties(Properties props) throws IOException ...{
        if (this.locations != null) ...{
            PropertiesPersister propertiesPersister = new DefaultPropertiesPersister();
            for (int i = 0; i < this.locations.length; i++) ...{
                Resource location = this.locations[i];
                if (logger.isInfoEnabled()) ...{
                    logger.info("Loading properties file from " + location);
                }
                InputStream is = null;
                try ...{
                    is = location.getInputStream();
                        //③ 加载密钥
                    Key key = DESEncryptUtil.getKey(keyLocation.getInputStream());
                    //④ 对属性文件进行解密
is = DESEncryptUtil.doDecrypt(key, is);
//⑤ 将解密后的属性流装载到props中
                    if(fileEncoding != null)...{
                        propertiesPersister.load(props,
        new InputStreamReader(is,fileEncoding));
                    }else...{
                        propertiesPersister.load(props ,is);
                    }
                } finally ...{
                    if (is != null)
                        is.close();
                }
            }
        }
    }
    }
}

    对locations指定的属性文件流数据进行额外的解密工作，解密后再装载到props中。比起PropertyPlaceholderConfigurer，我们只做了额外的一件事：装载前对属性资源进行解密。

    在代码清单 2的③和④处，我们使用了一个DES解密的工具类对加密的属性文件流进行解密。
    对文件进行对称加密的算法很多，一般使用DES对称加密算法，因为它速度很快，破解困难，DESEncryptUtil不但提供了DES解密功能，还提供了DES加密的功能，因为属性文件在部署前必须经常加密：
    代码清单 3 加密解密工具类

public class DESEncryptUtil ...{
    public static Key createKey() throws NoSuchAlgorithmException {//创建一个密钥
        Security.insertProviderAt(new com.sun.crypto.provider.SunJCE(), 1);
        KeyGenerator generator = KeyGenerator.getInstance("DES");
        generator.init(new SecureRandom());
        Key key = generator.generateKey();
        return key;
    }
    public static Key getKey(InputStream is) {
        try ...{
            ObjectInputStream ois = new ObjectInputStream(is);
            return (Key) ois.readObject();
        } catch (Exception e) ...{
            e.printStackTrace();
            throw new RuntimeException(e);
        }
    }
    private static byte[] doEncrypt(Key key, byte[] data) {//对数据进行加密
        try {
            Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, key);
            byte[] raw = cipher.doFinal(data);
            return raw;
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }
    }
    public static InputStream doDecrypt(Key key, InputStream in) {//对数据进行解密
        try {
            Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
            cipher.init(Cipher.DECRYPT_MODE, key);
            ByteArrayOutputStream bout = new ByteArrayOutputStream();
            byte[] tmpbuf = new byte[1024];
            int count = 0;
            while ((count = in.read(tmpbuf)) != -1) {
                bout.write(tmpbuf, 0, count);
                tmpbuf = new byte[1024];
            }
            in.close();
            byte[] orgData = bout.toByteArray();
            byte[] raw = cipher.doFinal(orgData);
            ByteArrayInputStream bin = new ByteArrayInputStream(raw);
            return bin;
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }
    }
    public static void main(String[] args) throws Exception {//提供了Java命令使用该工具的功能
        if (args.length == 2 && args[0].equals("key")) {// 生成密钥文件
            Key key = DESEncryptUtil.createKey();
            ObjectOutputStream oos = new ObjectOutputStream(
                    new FileOutputStream(args[1]));
            oos.writeObject(key);
            oos.close();
            System.out.println("成功生成密钥文件。");
        } else if (args.length == 3 && args[0].equals("encrypt")) {//对文件进行加密
            File file = new File(args[1]);
            FileInputStream in = new FileInputStream(file);
            ByteArrayOutputStream bout = new ByteArrayOutputStream();
            byte[] tmpbuf = new byte[1024];
            int count = 0;
            while ((count = in.read(tmpbuf)) != -1) {
                bout.write(tmpbuf, 0, count);
                tmpbuf = new byte[1024];
            }
            in.close();
            byte[] orgData = bout.toByteArray();
            Key key = getKey(new FileInputStream(args[2]));
            byte[] raw = DESEncryptUtil.doEncrypt(key, orgData);
            file = new File(file.getParent() + "\\en_" + file.getName());
            FileOutputStream out = new FileOutputStream(file);
            out.write(raw);
            out.close();
            System.out.println("成功加密，加密文件位于:"+file.getAbsolutePath());
        } else if (args.length == 3 && args[0].equals("decrypt")) {//对文件进行解密
            File file = new File(args[1]);
            FileInputStream fis = new FileInputStream(file);
            Key key = getKey(new FileInputStream(args[2]));
            InputStream raw = DESEncryptUtil.doDecrypt(key, fis);
            ByteArrayOutputStream bout = new ByteArrayOutputStream();
            byte[] tmpbuf = new byte[1024];
            int count = 0;
            while ((count = raw.read(tmpbuf)) != -1) {
                bout.write(tmpbuf, 0, count);
                tmpbuf = new byte[1024];
            }
            raw.close();
            byte[] orgData = bout.toByteArray();
            file = new File(file.getParent() + "\\rs_" + file.getName());
            FileOutputStream fos = new FileOutputStream(file);
            fos.write(orgData);
            System.out.println("成功解密，解密文件位于:"+file.getAbsolutePath());
        }
    }
}  

    解密工作主要涉及到两个类Cipher和Key，前者是加密器，可以通过init()方法设置工作模式和密钥，在这里，我们设置为解密工作模式：Cipher.DECRYPT_MODE。Cipher通过doFinal()方法对字节数组进行加密或解密。