11.3日学习笔记

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；
3.注意编程规范。

一、类图设计
Mermaid

classDiagram
class EncryptionAlgorithm {
<>
+encrypt(data: String): String
+decrypt(data: String): String
}

class DESAlgorithm {+encrypt(data: String): String+decrypt(data: String): String
}class IDEAAlgorithm {+encrypt(data: String): String+decrypt(data: String): String
}class EncryptionFactory {<<interface>>+createAlgorithm(): EncryptionAlgorithm
}class DESFactory {+createAlgorithm(): EncryptionAlgorithm
}class IDEAFactory {+createAlgorithm(): EncryptionAlgorithm
}class Client {-factory: EncryptionFactory+encryptData(data: String): String+decryptData(data: String): String
}EncryptionFactory ..> EncryptionAlgorithm : creates
DESFactory ..|> EncryptionFactory
IDEAFactory ..|> EncryptionFactory
DESFactory ..> DESAlgorithm : creates
IDEAFactory ..> IDEAAlgorithm : creates
EncryptionAlgorithm <|.. DESAlgorithm
EncryptionAlgorithm <|.. IDEAAlgorithm
Client ..> EncryptionFactory : uses

二、代码实现

1. 加密算法接口和实现类
   java

// EncryptionAlgorithm.java
public interface EncryptionAlgorithm {
String encrypt(String data) throws Exception;
String decrypt(String data) throws Exception;
}

// DESAlgorithm.java
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.util.Base64;

public class DESAlgorithm implements EncryptionAlgorithm {
private static final String ALGORITHM = "DES";
private SecretKey key;

public DESAlgorithm() throws Exception {// 生成密钥KeyGenerator keyGen = KeyGenerator.getInstance(ALGORITHM);keyGen.init(56); // DES使用56位密钥this.key = keyGen.generateKey();
}@Override
public String encrypt(String data) throws Exception {Cipher cipher = Cipher.getInstance(ALGORITHM);cipher.init(Cipher.ENCRYPT_MODE, key);byte[] encryptedBytes = cipher.doFinal(data.getBytes());return Base64.getEncoder().encodeToString(encryptedBytes);
}@Override
public String decrypt(String data) throws Exception {Cipher cipher = Cipher.getInstance(ALGORITHM);cipher.init(Cipher.DECRYPT_MODE, key);byte[] decryptedBytes = cipher.doFinal(Base64.getDecoder().decode(data));return new String(decryptedBytes);
}

}

// IDEAAlgorithm.java
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.util.Base64;

public class IDEAAlgorithm implements EncryptionAlgorithm {
private static final String ALGORITHM = "IDEA";
private SecretKey key;

public IDEAAlgorithm() throws Exception {// 生成密钥KeyGenerator keyGen = KeyGenerator.getInstance(ALGORITHM);keyGen.init(128); // IDEA使用128位密钥this.key = keyGen.generateKey();
}@Override
public String encrypt(String data) throws Exception {Cipher cipher = Cipher.getInstance(ALGORITHM);cipher.init(Cipher.ENCRYPT_MODE, key);byte[] encryptedBytes = cipher.doFinal(data.getBytes());return Base64.getEncoder().encodeToString(encryptedBytes);
}@Override
public String decrypt(String data) throws Exception {Cipher cipher = Cipher.getInstance(ALGORITHM);cipher.init(Cipher.DECRYPT_MODE, key);byte[] decryptedBytes = cipher.doFinal(Base64.getDecoder().decode(data));return new String(decryptedBytes);
}

}
2. 工厂接口和实现类
java

// EncryptionFactory.java
public interface EncryptionFactory {
EncryptionAlgorithm createAlgorithm() throws Exception;
}

// DESFactory.java
public class DESFactory implements EncryptionFactory {
@Override
public EncryptionAlgorithm createAlgorithm() throws Exception {
return new DESAlgorithm();
}
}

// IDEAFactory.java
public class IDEAFactory implements EncryptionFactory {
@Override
public EncryptionAlgorithm createAlgorithm() throws Exception {
return new IDEAAlgorithm();
}
}
3. 客户端类
java

// Client.java
public class Client {
private EncryptionFactory factory;
private EncryptionAlgorithm algorithm;

public Client(EncryptionFactory factory) throws Exception {this.factory = factory;this.algorithm = factory.createAlgorithm();
}public String encryptData(String data) throws Exception {return algorithm.encrypt(data);
}public String decryptData(String encryptedData) throws Exception {return algorithm.decrypt(encryptedData);
}public void setFactory(EncryptionFactory factory) throws Exception {this.factory = factory;this.algorithm = factory.createAlgorithm();
}

}
4. 测试类
java

// EncryptionTest.java
import java.util.Scanner;

public class EncryptionTest {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);

    try {System.out.println("=== 加密算法系统 ===");System.out.println("1. DES加密算法");System.out.println("2. IDEA加密算法");System.out.print("请选择加密算法(1-2): ");int choice = scanner.nextInt();scanner.nextLine(); // 消费换行符EncryptionFactory factory = null;String algorithmName = "";switch (choice) {case 1:factory = new DESFactory();algorithmName = "DES";break;case 2:factory = new IDEAFactory();algorithmName = "IDEA";break;default:System.out.println("无效选择！");return;}Client client = new Client(factory);while (true) {System.out.println("\n=== " + algorithmName + "加密系统 ===");System.out.println("1. 加密数据");System.out.println("2. 解密数据");System.out.println("3. 切换加密算法");System.out.println("4. 退出");System.out.print("请选择操作(1-4): ");int operation = scanner.nextInt();scanner.nextLine(); // 消费换行符switch (operation) {case 1:System.out.print("请输入要加密的文本: ");String plainText = scanner.nextLine();String encrypted = client.encryptData(plainText);System.out.println("加密结果: " + encrypted);break;case 2:System.out.print("请输入要解密的文本: ");String encryptedText = scanner.nextLine();String decrypted = client.decryptData(encryptedText);System.out.println("解密结果: " + decrypted);break;case 3:System.out.println("\n=== 切换加密算法 ===");System.out.println("1. DES加密算法");System.out.println("2. IDEA加密算法");System.out.print("请选择加密算法(1-2): ");int newChoice = scanner.nextInt();scanner.nextLine();switch (newChoice) {case 1:client.setFactory(new DESFactory());algorithmName = "DES";System.out.println("已切换到DES算法");break;case 2:client.setFactory(new IDEAFactory());algorithmName = "IDEA";System.out.println("已切换到IDEA算法");break;default:System.out.println("无效选择！");}break;case 4:System.out.println("感谢使用！");return;default:System.out.println("无效选择！");}}} catch (Exception e) {System.err.println("错误: " + e.getMessage());e.printStackTrace();} finally {scanner.close();}
}

}
三、使用说明
编译运行：
bash

javac *.java
java EncryptionTest
功能特点：
支持DES和IDEA两种加密算法
可以动态切换加密算法
提供加密和解密功能
使用Base64编码显示加密结果
注意事项：
需要Java 8或更高版本
IDEA算法可能需要额外的加密库支持（如Bouncy Castle）
每次实例化都会生成新的密钥
四、扩展建议
可以添加AES、RSA等其他加密算法
实现密钥的保存和加载功能
添加文件加密/解密功能
实现加密强度配置