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
- 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
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