java - 如何在没有文件输出的情况下用Java显示解密文件？

Question

我正在尝试开发一个系统，该系统将解密一个文件，然后允许授权用户在不保存解密文件的情况下查看它。这是为了确保其他用户无法打开解密后的文件。

以下代码产生了一个文件输出。

    public NewJFrame() {try{
                String key = "squirrel123";
                FileInputStream fis2 = newFileInputStream("encrypted.mui");
                FileOutputStream fos2 = new FileOutputStream("decrypt.rar");

                decrypt(key, fis2, fos2);
                Desktop dk=Desktop.getDesktop();
                File f = new File("decrypt.rar");
                dk.open(f);
            }
                catch (Throwable e) {
         JOptionPane.showMessageDialog(null, e);
    }}  
    public static void decrypt(String key, InputStream is, OutputStream os) throws Throwable {
    encryptOrDecrypt(key, Cipher.DECRYPT_MODE, is, os);
}

public static void encryptOrDecrypt(String key, int mode, InputStream is, OutputStream os) throws Throwable {

    DESKeySpec dks = new DESKeySpec(key.getBytes());
    SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");
    SecretKey desKey = skf.generateSecret(dks);
    Cipher cipher = Cipher.getInstance("DES"); // DES/ECB/PKCS5Padding for SunJCE

    if (mode == Cipher.ENCRYPT_MODE) {
        cipher.init(Cipher.ENCRYPT_MODE, desKey);
        CipherInputStream cis = new CipherInputStream(is, cipher);
        doCopy(cis, os);
    } else if (mode == Cipher.DECRYPT_MODE) {
        cipher.init(Cipher.DECRYPT_MODE, desKey);
        CipherOutputStream cos = new CipherOutputStream(os, cipher);
        doCopy(is, cos);
    }
}

public static void doCopy(InputStream is, OutputStream os) throws IOException {
    byte[] bytes = new byte[64];
    int numBytes;
    while ((numBytes = is.read(bytes)) != -1) {
        os.write(bytes, 0, numBytes);
    }
    os.flush();
    os.close();
    is.close();
}

如何在不使用 FileOutputStream 的情况下解密文件，然后允许授权用户在解密后查看它？

Answer 1

如果您不想将其写入物理文件，而只是呈现数据，您可以使用与 FileOutputStream 不同的编写器。

比如可以创建一对PipedStream，解密后读取结果。

        String key = "squirrel123";
        FileInputStream fis2 = newFileInputStream("encrypted.mui");

        PipedInputStream pis = new PipedInputStream();
        PipedOutputStream pos = new PipedOutputStream(pis);

        decrypt(key, fis2, pis);

        BufferedReader reader = new BufferedReader(new InputStreamReader(pis));
        String line;
        while( (line=reader.readLine()) != null ){
            System.out.println(line);
        }