java加密方式MD5、RSA、AES等工具类

当涉及到Java中的加密方式，可以使用以下工具类来实现MD5、RSA和AES加密：

1. MD5 加密工具类：

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5Util {
    public static String encrypt(String input) {
        try {
            MessageDigest md = MessageDigest.getInstance("MD5");
            byte[] messageDigest = md.digest(input.getBytes());
            StringBuilder hexString = new StringBuilder();
            for (byte b : messageDigest) {
                hexString.append(String.format("%02x", b));
            }
            return hexString.toString();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
            return null;
        }
    }
}

使用示例：

String encryptedText = MD5Util.encrypt("Hello World");
System.out.println(encryptedText);

1. RSA 加密工具类：

import java.nio.charset.StandardCharsets;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import javax.crypto.Cipher;

public class RSAUtil {
    public static KeyPair generateKeyPair(int keySize) {
        try {
            KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
            keyPairGenerator.initialize(keySize);
            return keyPairGenerator.generateKeyPair();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
            return null;
        }
    }

    public static byte[] encrypt(String plaintext, PublicKey publicKey) {
        try {
            Cipher cipher = Cipher.getInstance("RSA");
            cipher.init(Cipher.ENCRYPT_MODE, publicKey);
            return cipher.doFinal(plaintext.getBytes(StandardCharsets.UTF_8));
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    public static String decrypt(byte[] ciphertext, PrivateKey privateKey) {
        try {
            Cipher cipher = Cipher.getInstance("RSA");
            cipher.init(Cipher.DECRYPT_MODE, privateKey);
            byte[] decryptedBytes = cipher.doFinal(ciphertext);
            return new String(decryptedBytes, StandardCharsets.UTF_8);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    public static PublicKey getPublicKey(byte[] publicKeyBytes) {
        try {
            X509EncodedKeySpec keySpec = new X509EncodedKeySpec(publicKeyBytes);
            KeyFactory keyFactory = KeyFactory.getInstance("RSA");
            return keyFactory.generatePublic(keySpec);
        } catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
            e.printStackTrace();
            return null;
        }
    }

    public static PrivateKey getPrivateKey(byte[] privateKeyBytes) {
        try {
            PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(privateKeyBytes);
            KeyFactory keyFactory = KeyFactory.getInstance("RSA");
            return keyFactory.generatePrivate(keySpec);
        } catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
            e.printStackTrace();
            return null;
        }
    }
}

使用示例：

// 生成密钥对
KeyPair keyPair = RSAUtil.generateKeyPair(2048);
PublicKey publicKey = keyPair.getPublic();
PrivateKey privateKey = keyPair.getPrivate();

// 加密
String plaintext = "Hello World";
byte[] ciphertext = RSAUtil.encrypt(plaintext, publicKey);

// 解密
String decryptedText = RSAUtil.decrypt(ciphertext, privateKey);
System.out.println(decryptedText);

1. AES 加密工具类：

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.nio.charset.StandardCharsets;
import java.security.Key;

public class AESUtil {
    public static byte[] encrypt(String plaintext, Key key) {
        try {
            Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, key);
            return cipher.doFinal(plaintext.getBytes(StandardCharsets.UTF_8));
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    public static String decrypt(byte[] ciphertext, Key key) {
        try {
            Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
            cipher.init(Cipher.DECRYPT_MODE, key);
            byte[] decryptedBytes = cipher.doFinal(ciphertext);
            return new String(decryptedBytes, StandardCharsets.UTF_8);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    public static Key generateKey() {
        String keyString = "YourSecretKey"; // 密钥字符串
        byte[] keyBytes = keyString.getBytes(StandardCharsets.UTF_8);
        return new SecretKeySpec(keyBytes, "AES");
    }
}

使用示例：

// 生成密钥
Key key = AESUtil.generateKey();

// 加密
String plaintext = "Hello World";
byte[] ciphertext = AESUtil.encrypt(plaintext, key);

// 解密
String decryptedText = AESUtil.decrypt(ciphertext, key);
System.out.println(decryptedText);

这些是在Java中实现MD5、RSA和AES加密的简单示例。请根据自己的需求进行调整和扩展。

注意：这些示例仅供参考，并不涵盖完整的加密实现和安全性考虑。在实际应用中，建议使用成熟的加密库或框架来确保安全性。