软件设计三

 

 

实验3：工厂方法模式

本次实验属于模仿型实验，通过本次实验学生将掌握以下内容：

1、理解工厂方法模式的动机，掌握该模式的结构；

2、能够利用工厂方法模式解决实际问题。

 

[实验任务一]：加密算法

目前常用的加密算法有DES（Data Encryption Standard）和IDEA（International Data Encryption Algorithm）国际数据加密算法等，请用工厂方法实现加密算法系统。

实验要求：

1.  画出对应的类图；

 

 

2.  提交该系统的代码，该系统务必是一个可以能够直接使用的系统，查阅资料完成相应加密算法的实现；

Encryption：

public interface Encryption

{

    String encrypt(String text);

 

    String decrypt(String ciphertext);

}

DES：

public class DES implements Encryption

{

    private SecretKey secretKey;

 

    public DES()

    {

        try

        {

            KeyGenerator keyGenerator = KeyGenerator.getInstance("DES");

            secretKey = keyGenerator.generateKey();

        }

        catch (Exception e)

        {

            e.printStackTrace();

        }

    }

 

    //DES加密

    @Override

    public String encrypt(String text)

    {

        try

        {

            Cipher cipher = Cipher.getInstance("DES");

            cipher.init(Cipher.ENCRYPT_MODE, secretKey);

            byte[] encryptedBytes = cipher.doFinal(text.getBytes(StandardCharsets.UTF_8));

            return Base64.getEncoder().encodeToString(encryptedBytes);

        }

        catch (Exception e)

        {

            e.printStackTrace();

            return null;

        }

    }

 

    //DES解密

    @Override

    public String decrypt(String ciphertext)

    {

        try

        {

            Cipher cipher = Cipher.getInstance("DES");

            cipher.init(Cipher.DECRYPT_MODE, secretKey);

            byte[] decryptedBytes = cipher.doFinal(Base64.getDecoder().decode(ciphertext));

            return new String(decryptedBytes, StandardCharsets.UTF_8);

        }

        catch (Exception e)

        {

            e.printStackTrace();

            return null;

        }

    }

}

 

IDEA：

public class IDEA implements Encryption

{

    private SecretKey secretKey;

 

    static

    {

        // 添加Bouncy Castle提供程序

        Security.addProvider(new BouncyCastleProvider());

    }

 

    public IDEA()

    {

        try

        {

            KeyGenerator keyGenerator = KeyGenerator.getInstance("IDEA", "BC");

            secretKey = keyGenerator.generateKey();

        }

        catch (Exception e)

        {

            e.printStackTrace();

        }

    }

 

    @Override

    public String encrypt(String text)

    {

        try

        {

            // 创建一个IDEA加密器

            Cipher cipher = Cipher.getInstance("IDEA/ECB/PKCS5Padding", "BC");

            cipher.init(Cipher.ENCRYPT_MODE, secretKey);

            byte[] encryptedBytes = cipher.doFinal(text.getBytes());

            return Base64.getEncoder().encodeToString(encryptedBytes);

        }

        catch (Exception e)

        {

            e.printStackTrace();

            return null;

        }

    }

 

    @Override

    public String decrypt(String ciphertext)

    {

        try

        {

            Cipher cipher = Cipher.getInstance("IDEA/ECB/PKCS5Padding", "BC");

            cipher.init(Cipher.DECRYPT_MODE, secretKey);

            byte[] encryptedBytes = Base64.getDecoder().decode(ciphertext);

            return new String(cipher.doFinal(encryptedBytes), StandardCharsets.UTF_8);

        }

        catch (Exception e)

        {

            e.printStackTrace();

            return null;

        }

    }

}

EncryptionFactory

public interface EncryptionFactory

{

    Encryption createEncryption();

}

 

DESFactory：

public class DESFactory implements EncryptionFactory

{

    @Override

    public Encryption createEncryption()

    {

        return new DES();

    }

}

 

 

IDEAFactory：

public class IDEAFactory implements EncryptionFactory

{

    @Override

    public Encryption createEncryption()

    {

        return new IDEA();

    }

}

 

 

FactoryMethod：

import java.util.Scanner;

 

public class FactoryMethod

{

    public static void main(String[] args)

    {

        Scanner sc = new Scanner(System.in);

        System.out.println("请输入要加密的文本：");

        String text = sc.next();

 

        EncryptionFactory factory = null;

 

        System.out.println("请输入加密算法编号：\n" +

                "1、DES加密  2、IDEA加密"  3、退出);

        int choose = sc.nextInt();

        if (choose == 1)

        {

            //DES加密

            factory = new DESFactory();

            System.out.println("DES加密");

        } else if (choose == 2)

        {

            //IDEA加密

            factory = new IDEAFactory();

            System.out.println("IDEA加密");

        }

 

        Encryption encryptionAlgorithm = factory.createEncryption();

        String encryptedText = encryptionAlgorithm.encrypt(text);

        String decryptedText = encryptionAlgorithm.decrypt(encryptedText);

        System.out.println("原文本：" + text);

        System.out.println("加密后：" + encryptedText);

        System.out.println("解密后：" + decryptedText);

    }

}

 

运行结果：